3
Transportation Risk

The original statement of task for this study (Sidebar 1.1) directs the committee to examine the “principal risks” for transporting spent fuel and high-level waste; determine how well these risks are understood; and compare them to other risks that confront members of society. Those tasks are addressed in this chapter.

As noted in Chapter 1, risk is a multidimensional concept: It includes health and safety risks that arise from exposures of workers and members of the public to radiation from shipments of spent fuel and high-level waste. It also includes social risks that arise from social processes1 and people’s perceptions,2 even in the absence of radiation exposures. The health and safety risks and social risks are collectively referred to as societal risks in the statement of task given in Sidebar 1.1.

A great deal of work has been carried out over the past four decades to understand the risks (Sidebar 3.1) arising from the transport of spent fuel, both in the United States and abroad. Although the principal focus of this

1  

Social process is defined as “a characteristic mode of social interaction” (Webster’s Third New International Dictionary). Social interactions shape the communities in which people live by, for example, influencing choices about where to purchase or rent a home, where to work, and where to send children to school.

2  

Perception is defined as the “integration of sensory impressions of events in the external world … as a function of nonconscious expectations derived from past experience” (Webster’s Third New International Dictionary). Perceptions can have a strong influence on peoples’ behavior, whether or not such perceptions are an accurate picture of reality.



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Going the Distance? The Safe Transport of Spent Nuclear Fuel and High-Level Radioactive Waste in the United States 3 Transportation Risk The original statement of task for this study (Sidebar 1.1) directs the committee to examine the “principal risks” for transporting spent fuel and high-level waste; determine how well these risks are understood; and compare them to other risks that confront members of society. Those tasks are addressed in this chapter. As noted in Chapter 1, risk is a multidimensional concept: It includes health and safety risks that arise from exposures of workers and members of the public to radiation from shipments of spent fuel and high-level waste. It also includes social risks that arise from social processes1 and people’s perceptions,2 even in the absence of radiation exposures. The health and safety risks and social risks are collectively referred to as societal risks in the statement of task given in Sidebar 1.1. A great deal of work has been carried out over the past four decades to understand the risks (Sidebar 3.1) arising from the transport of spent fuel, both in the United States and abroad. Although the principal focus of this 1   Social process is defined as “a characteristic mode of social interaction” (Webster’s Third New International Dictionary). Social interactions shape the communities in which people live by, for example, influencing choices about where to purchase or rent a home, where to work, and where to send children to school. 2   Perception is defined as the “integration of sensory impressions of events in the external world … as a function of nonconscious expectations derived from past experience” (Webster’s Third New International Dictionary). Perceptions can have a strong influence on peoples’ behavior, whether or not such perceptions are an accurate picture of reality.

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Going the Distance? The Safe Transport of Spent Nuclear Fuel and High-Level Radioactive Waste in the United States SIDEBAR 3.1 Background on Risk Risks for spent fuel and high-level waste transportation arise from conventional vehicular accidents and exposures to ionizing radiation under both normal and accident conditions. Radiation risks are primarily a concern for people who live near, or travel on, spent fuel shipment routes. Risk considers both the likelihood of occurrence of a specific hazard and its consequences. Frequently, one considers several scenarios that involve different kinds of hazards, each with a different likelihood of occurrence and consequence. One way in which risk can be expressed is in terms of a triplet (Kaplan and Garrick, 1981): Where, for spent fuel shipments, Scenarios represents transport conditions that can lead to an exposure to ionizing radiation from either routine operations or severe accidents, Probability expresses quantitatively the likelihood that a scenario will actually occur during one shipment; it is expressed as a dimensionless quantity that ranges in value from 0 (impossible) to 1 (certain)—for example, a probability of 0.5 indicates that a particular scenario has a 50 percent chance of occurring, and Consequences describe the undesirable results if the scenario does occur: for example, undesirable health effects. The risks from spent nuclear fuel transport can be characterized by several measures. For example, risk can be expressed in terms of the expected number of deaths per quantity of spent fuel transported, per number of packages shipped, or per number of package shipments. It also could be expressed in terms of the number of deaths expected for a specific subpopulation exposed to ionizing radiation, for example, the subpopulation of transportation workers. Although they are difficult to quantify, consequences may also include socioeconomic outcomes. The choice of scenarios and consequences selected for a risk calculation can make a difference in how that risk is understood by potentially affected populations. A risk may be understood as low by one measure in comparison to another, even though the same risk is being considered (NRC, 1996). This has implications for informing decision makers, for communicating about risks with non-experts, and for the legitimacy of risk comparisons in the eyes of interested and affected people (NRC, 1989, 1996). Comparing risks arising from fundamentally different activities also requires care in the selection of appropriate scenarios and consequences. This point is discussed in more detail elsewhere in this chapter. report is on transportation in the United States, much can be learned from international experiences. Spent fuel and high-level waste are being transported in many other countries, in some cases in much greater quantities than in the United States. The committee has drawn upon the experiences

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Going the Distance? The Safe Transport of Spent Nuclear Fuel and High-Level Radioactive Waste in the United States of foreign transportation programs to inform its judgments. This information has been acquired through the review of published documents and from first-hand experience.3 Transportation risks can arise both during normal transport operations and from accidents involving loaded spent fuel or high-level waste shipping packages.4 Table 3.1 describes the transportation impacts for these two operational scenarios. These risks can also arise from incidents (e.g., terrorist attacks) involving packages containing spent fuel or high-level waste; such incidents are not addressed in this report (see Section 1.2). The health and safety risks to be discussed in this chapter arise from exposures of people who travel, work, or live near transportation routes, and transportation workers themselves, to radiation (Sidebar 3.2) from loaded spent fuel and high-level waste transportation packages. During normal operations, such exposures can occur as the result of radiation shine5 from transportation packages loaded with spent fuel or high-level waste. Although the radiation doses to individuals near transport routes are likely to be very low, large numbers of individuals may receive exposures, producing a “collective dose” that can be used to estimate health impacts (see Sidebar 3.3). Degradation and/or loss of package containment in a severe accident has the potential to increase such radiation exposures and possibly result in the release of radioactive material from the package to the environment, although the committee notes in Chapter 2 that the robust design of transportation packages makes such releases unlikely. Health and safety risks are frequently characterized in terms of human health effects: for example, injuries and loss of human life. Modern society generally considers such consequences to be the most severe harms that can 3   Committee member Clive Young has extensive experience with the transport of spent fuel in the United Kingdom. In addition, a group of committee members visited Germany and the United Kingdom in September 2004 (see Appendix B) to obtain first-hand information about European transportation programs. 4   International Atomic Energy Agency regulations for the safe transport of radioactive materials define three levels of severity for transportation conditions: routine conditions of transport, normal conditions of transport, and accident conditions of transport. Routine conditions are free of any transport mishaps; normal conditions can involve minor mishaps due to rough handling or exposure to weather. Accidents subject packages to severe conditions that well exceed normal conditions of transport. 5   Transportation packages contain heavy shielding to protect workers and the public from the radiation emitted by the spent fuel or high-level waste contained within them. The packages are effective in shielding well over 99 percent of this emitted radiation, but a small amount (below regulatory limits) of radiation, primarily gamma rays, can escape from the interior of the packages and provide external doses to workers and the public. This report uses the term radiation shine to refer to this external radiation.

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Going the Distance? The Safe Transport of Spent Nuclear Fuel and High-Level Radioactive Waste in the United States TABLE 3.1 Transportation Risks Examined in this Report Transportation Conditions Transportation Impacts Health and Safety Risks Social Risks Normal Health impacts arising from the emission of radiation (i.e., radiation shine) from transportation packages Direct socioeconomic impacts: loss of economic or social well-being as a direct result of transportation program operations     Perception-based impacts: anxiety and associated illness; loss of property values; and reduced economic activity Accidents Health and environmental impacts arising from elevated radiation and/or the physical release of radioactive material as a result of the degradation or loss of package containment Direct socioeconomic impacts: Temporary loss of transportation route use and associated business disruptions such as a loss of tourism     Perception-based impacts: social amplification of the normal impacts as a result of accidents; these can result in secondary or tertiary impacts, including stigmatization of people and places; loss of trust in transportation program management; moratorium on transportation program operations; and/or increased program costs result from any hazard, especially anthropogenic hazards that can be controlled through regulation. Society places a high value on human life and routinely demands that governments strictly regulate life-threatening hazards. Reductions in severe injuries and loss of human life are generally considered to be primary measures of regulatory effectiveness. Because of this emphasis on protecting human life, risk assessment experts have developed methodologies to quantitatively estimate risks to human life. Sidebar 3.1 provides a description of one way in which such risks are estimated.

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Going the Distance? The Safe Transport of Spent Nuclear Fuel and High-Level Radioactive Waste in the United States Social risks can have both direct socioeconomic and perception-based impacts such as those shown in Table 3.1. These risks may reduce the desirability of living and working in communities associated with spent fuel and high-level waste transportation operations. The social risks of interest in this chapter are harder to measure than the corresponding health and safety risks, and even identifying cause-and-effect relationships can be difficult. The impacts of social risk occur within a much larger sphere of social and economic activities that can mask important effects. The measurement of perception-based impacts can be especially difficult, because it frequently requires the use of surveys to measure people’s anticipated, rather than actual, behaviors. The health and safety risks and the social risks associated with spent fuel and high-level waste transportation can have significant interactions. Increases in radiation exposures or in the incidence of health effects from transportation operations (e.g., because of well-publicized mishaps, accidents, or fatalities) may, over time, increase the perception-based impacts. On the other hand, transportation operations that are carried out without demonstrable health impacts may, over time, reduce the perception-based impacts. A shipping incident or accident that leads to a moratorium on transportation operations might well change the entire profile of social risks associated with a transportation program. There is another class of nonradiological impacts that are not considered in detail in this chapter: conventional vehicular impacts associated with the transportation of spent fuel and high-level waste. These include the health impacts of exhaust emissions from transport conveyances and vehicular accidents that result in fatalities, injuries, and property damage. While these impacts are real and predictable, they generally do not garner the same level of awareness or concern among members of the public as the radiation-based impacts described previously. Moreover, it could be argued that given the higher standards for driver training and equipment maintenance, and the conduct of vehicle and package inspections and operations for spent fuel and high-level waste transportation, conventional vehicular impacts associated with accidents would actually be lower than for other types of hazardous materials or heavy-freight transport. In any case, spent fuel and high-level waste transportation programs are a very small component of the overall transport system for hazardous materials, as measured both by load mass and by volume of traffic. The committee provides an examination of health and safety risks of spent fuel and high-level waste transportation in Section 3.1. The social risks are examined in Section 3.2, and the risk comparisons called for by the study charge (see Sidebar 1.1) are described in Section 3.3. The committee’s findings and recommendations on transportation risks are provided in Section 3.4.

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Going the Distance? The Safe Transport of Spent Nuclear Fuel and High-Level Radioactive Waste in the United States SIDEBAR 3.2 Radiation Dose Materials that are radioactive are unstable (i.e., the nuclei in the atoms of the material possess too much energy) and transform spontaneously (decay) through the emission of radiation. This radiation may be in the form of energetic particles, such as alpha particles, beta particles, or neutrons, or energy may be emitted in the form of electromagnetic radiation (e.g., gamma rays). Collectively these emissions are known as ionizing radiation because they are sufficiently energetic to directly or indirectly ionize the matter (i.e., remove electrons from the atoms) they travel through. Absorption of radiation energy by a cell of a living organism can alter its chemical and physical state. The absorption of large amounts of radiation can produce short-term or “acute” effects in the cell. The most severe effect would be cell death. Small amounts of radiation (not sufficient to cause cell death) potentially can damage the cell’s genetic material (i.e., DNA contained in the chromosomes). If the cell’s natural repair mechanisms cannot repair this damage correctly, it may lead to the induction of cancer at some future time. Because of the long time periods involved in their development, such cancers are referred to as “latent.” The following quantities are commonly used to characterize radiation exposures in living organisms: Absorbed dose. The quantity of ionizing radiation deposited into an organ or tissue, expressed in terms of the energy absorbed per unit mass of tissue. The basic unit of absorbed dose is the rad or its SI (international system of units, also known as the metric system) alternative the gray (Gy; 1 Gy = 100 rad). Equivalent dose. The absorbed dose averaged over the organ or tissue of interest multiplied by a weighting factor that accounts for the differences in biological effects (per unit of absorbed dose) for different types of radiation. The weighting factor ranges from 1 for X-rays and gamma rays to 20 for alpha particles and some neutrons. The equivalent dose is expressed in units of rem or its SI alternative the sievert (Sv; 1 Sv = 100 rem). Effective dose. A measure of dose that accounts for the differences in biological effects of different types of radiation and for the varying sensitivity of different organs to the biological effects of radiation. Effective doses are also expressed in rem or sieverts. Radiation and radioactivity can be found in nature in a number of different forms. The natural radiation environment consists of cosmic and solar radiation, external radiation from radioactive materials present in rocks and soil, and inhaled 3.1 HEALTH AND SAFETY RISKS Two approaches are used in this section to estimate the health and safety risks of spent fuel and high-level waste transportation: (1) an examination of the worldwide record of spent fuel transport (Section 3.1.1); and

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Going the Distance? The Safe Transport of Spent Nuclear Fuel and High-Level Radioactive Waste in the United States and ingested radioactive materials from air, food, and water. These sources have been present since the creation of Earth and provide an effective dose to all living organisms. The table below shows that, worldwide, the average annual effective dose to individuals is about 2.4 millisieverts (mSv; 240 millirem). This annual exposure is a good starting point to use in judging the magnitude of equivalent doses received from man-made sources. The National Council on Radiation Protection and Measurements (NCRP, 1987) estimates that man-made sources of radiation and radioactivity contribute an additional effective dose of 0.6 mSv (60 millirem) annually to an average person living in the United States. Most of this dose is due to medical procedures such as diagnostic X-rays and nuclear medicine procedures. Since the NCRP report was published, new diagnostic medical procedures that utilize ionizing radiation (especially computed tomography scanning) have come into wide use in the United States. Consequently, the average annual doses from medical procedures are probably increasing. It is important to keep in mind that the effective dose statistics presented in this sidebar are averages. Individuals can receive much more or much less than the average depending on where they live (i.e., location as well as height above sea level), the type of house in which they reside, their occupation, the medical procedures they undergo, and many other factors determined by the individual life-style (e.g., air travel, watching television, diet). TABLE Worldwide Exposure to Natural Sources of Radiation and Radioactive Material Source of Exposure Average Annual Effective Dose, mSv (millirem) Typical Range of Effective Doses, mSv (millirem) Cosmic radiation 0.39 (39) 0.3–1.0 (30–100) External terrestrial radiation 0.48 (48) 0.3–0.6 (30–60) Inhalation (U, Th, 222Rn, 220Rn) 1.26 (126) 0.2–10.0 (20–1,000) Ingestion (40K) 0.29 (29) 0.2–0.8 (20–80) Total 2.42 (242) 1.0–10.0 (100–1,000)   SOURCE: Adapted from UNSCEAR (2000, Annex B, Table 31). (2) an examination of the principal quantitative risk analyses that have been carried out for spent fuel and high-level waste transport, including the analysis for transporting spent fuel and high level-waste to a federal repository at Yucca Mountain, Nevada (Section 3.1.2).

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Going the Distance? The Safe Transport of Spent Nuclear Fuel and High-Level Radioactive Waste in the United States SIDEBAR 3.3 Collective Dose and Latent Cancer Fatalities Collective dose is defined as the sum of all radiation doses received by all members of a population at risk (NCRP, 1995). The units of collective dose are usually given as person-sieverts or person-rem. This concept is frequently used in radiation protection applications, both for controlling actual exposures and for estimating potential exposure risks. The use of the collective dose for radiation protection purposes assumes the following (NCRP, 1995): There is a direct proportionality between radiation dose and risk over their respective ranges of concern. Risk is independent of dose rate. A radiation dose leads to an identical risk whether it is administered to a single individual or to a population. NCRP (1995, p. 1) notes that “[w]hile these assumptions may or may not be valid, they are considered to be conservative and have been generally accepted by the scientific community concerned with radiation protection.” The Department of Energy (DOE) used the collective dose concept to estimate latent cancer fatalities (LCFs) in the final Yucca Mountain Environmental Impact Statement (EIS). These cancers are expected to be produced many years after a radiation dose is received (i.e., after a latency period) and are never traceable directly to the received dose. DOE calculated collective doses for populations of workers and the public from prospective exposures to radiation from its transportation program. These doses were calculated using computer programs such as RADTRAN (see Sidebar 3.4). DOE then estimated the number of latent cancer fatalities using the International Commission on Radiological Protection (ICRP, 1991) recommended conversion factors: 5 × 10−4 latent cancer fatality per person-rem (5 × 10−2 per person-sievert) of collective dose for the general public and 4 × 10−4 latent cancer fatality per person-rem (4 × 10−2 per person-sievert) of collective dose for workers; these factors were doubled when doses greater than 20 rem are received over short time periods. The conversion factor for the public is higher because it applies over an entire lifetime, whereas the factor for workers applies only for working ages. Radiation is a weak carcinogen at the low doses involved in the routine transport of spent fuel and high-level waste. Consequently, the incremental increase in latent cancers from low doses of radiation is very small relative to the natural occurrence of this disease in human populations. Moreover, radiation-induced cancers do not have any special characteristics that allow them to be differentiated from cancers developed from other causes. 3.1.1 Historical Record of Spent Fuel Transport Spent fuel has been transported routinely in more than a dozen countries, including the United States, for many decades. The quality of record keeping on these shipments varies significantly, especially between the mid-

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Going the Distance? The Safe Transport of Spent Nuclear Fuel and High-Level Radioactive Waste in the United States 1940s and 1970s. The committee first provides a brief review of the transportation experience in the United States and then examines experiences in some other countries. U.S. Transportation Experience The United States has been transporting irradiated nuclear fuel since World War II. The first irradiated fuel shipments were made by the Manhattan Project as part of the national effort to develop atomic weapons. More than 170,000 MTHM6 of irradiated fuel were transported within the Hanford (Washington) and Savannah River (South Carolina) sites as part of the nuclear weapons production effort between 1944 and the end of the Cold War in the late 1980s. Most of this transport occurred over very short distances (a few kilometers [miles]) on publicly restricted lands, mostly by rail. By the early 1960s, civilian spent fuel was being transported routinely on the nation’s road and rail systems by the Atomic Energy Commission (AEC).7 In 1974, the AEC was reorganized,8 and authority for regulating the commercial transport of radioactive materials transportation was given to the newly established U.S. Nuclear Regulatory Commission (USNRC). The most complete records of spent fuel transportation date from the creation of this agency. Most spent fuel transport across the nation’s public highways and private railroads has involved small-quantity shipments of commercial spent fuel. Estimates of quantities of commercial spent fuel shipments are available from several sources. Pope et al. (1991, 2001) provide commercial spent fuel shipping estimates since 1964. These estimates were developed from Department of Energy (DOE) and Department of Transportation (DOT) databases supplemented with data from the USNRC and private sources. Pope et al. (1991) note that their estimates do not include shipments from six commercial reactors because of the difficulty in obtaining data. 6   Metric tons of heavy metal, where the heavy metal is uranium. This is a commonly used measure of fuel quantity. For comparison purposes, a typical reactor core contains about 100 MTHM (110 short tons) of nuclear fuel. A typical truck transport package typically holds between 0.5 and 2 MTHM (0.55 and 2.2 short tons) of spent fuel; a typical rail package holds between 10 and 18 MTHM (11 and 20 short tons). 7   The AEC was created by the Atomic Energy Act (also known as the McMahon Act) in 1946 to control and promote the use of nuclear power. 8   The Energy Reorganization Act of 1974 abolished the AEC and created two federal agencies in its place: the Nuclear Regulatory Commission and the Energy Research and Development Administration. The Energy Research and Development Administration became the Department of Energy after the Energy Reorganization Act of 1977.

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Going the Distance? The Safe Transport of Spent Nuclear Fuel and High-Level Radioactive Waste in the United States TABLE 3.2 Commercial Spent Nuclear Fuel Shipments in the United States, 1964–2004 Time Period Mass of Spent Fuel Shipped (MTHM) Number of Shipments Highway Rail Highway Rail 1964–1978 473 348 1565 126 1979–1997 356 1097 1181 153 1998–2004 16 766 102 261 Totals 845 2211 2848 540 NOTE: MTHM = metric tons of heavy metal. SOURCES: Pope et al. (1991, 2001); USNRC, written communication, 2005. Additional unpublished information was made available to the committee from Energy Resources International (Supko, 2000; Supko, 2005, written communication) and the USNRC (USNRC, 2005, written communication). The latter communication provided shipping data for 1998–2004 based on shipper notifications required under regulation 10 CFR Part 73.9 This communication is an update of USNRC’s public circular on spent fuel shipments (USNRC, 1998). Updated information has not been released since the September 2001 terrorist attacks. The agency was preparing an updated version for public release when the present report was being finalized in December 2005. Table 3.2 provides an estimate of commercial spent fuel shipments in the United States since 1964. The committee was not able to assess the completeness or accuracy of these data, except to note that the pre-1979 data are likely incomplete. Information on spent fuel shipments prior to 1964 is not available, although accident and incident reports dating back to the mid-1950s are available, as discussed elsewhere in this chapter. One conclusion that can be drawn from these data is that the previous U.S. spent fuel shipping experience as measured by the total number of shipments or mass of spent fuel shipped is small compared with anticipated future transportation campaigns. The federal repository and Private Fuel Storage, LLC, programs, for example, plan to ship about 20 and 13 times, respectively, the amount of commercial spent fuel that has been shipped in the United States since 1964. Moreover, both programs plan to ship spent fuel primarily by rail. The planned number of rail shipments to a federal 9   Code of Federal Regulations, Title 10, Part 73: Physical Protection of Plants and Materials.

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Going the Distance? The Safe Transport of Spent Nuclear Fuel and High-Level Radioactive Waste in the United States repository at Yucca Mountain under the mostly rail scenario (9600 shipments; see Table 3.8) is approximately 18 times the number of rail shipments that have occurred in the United States since 1964. Spent nuclear fuel shipments in the United States are usually made under the USNRC’s or DOT’s exclusive use regulations (10 CFR 71.47(b)).10 Such shipments can be transported using public road and rail systems in the United States only if they do not exceed the following dose limits: 2 millisieverts (mSv) per hour (200 millirem [mrem] per hour) (see Sidebar 3.2) on the external surface of the transport package11 and at any point on the outer surface of the vehicle. 0.1 mSv per hour (10 mrem per hour) at any point 2 meters (6.5 feet) from the outer lateral surfaces (but not the top or bottom) of the vehicle. 0.02 mSv per hour (2 mrem per hour) in any normally occupied space. This provision does not apply to private carriers if exposed personnel under their control wear approved radiation dosimetry devices.12 U.S. agencies do not collect records of radiation exposures resulting from the transportation of irradiated nuclear fuel as is done for personnel exposures in nuclear power plants. Private carriers will keep records for those workers who use radiation monitoring devices in accordance with regulations, but these records are not published. Consequently, the doses received by workers and the public associated with spent nuclear fuel shipments in the United States are not precisely known, although the committee judges that they are likely to be relatively small given the external dose limits allowed by regulations combined with the small numbers of shipments that have been made to date. Estimates of doses to populations and to hypothesized maximally exposed individuals in future shipments have been made by the USNRC, DOE, and DOT based on the projected number and characteristics of shipments and the populations that live in the proximity of planned transportation routes. These estimates have generally assumed that the dose rates from the packages are the maximum allowed 10   Exclusive use is defined in 10 CFR 71.4 as “sole use by a single consignor of a conveyance for which all initial, intermediate, and final loading and unloading are carried out in accordance with the direction of the consignor or consignee. The loading and unloading must be carried out by personnel having radiological training and resources appropriate for the safe handling of the consignment.” 11   A limit of 10 mSv per hour (1000 mrem per hour) applies when the shipment is made in a closed transport vehicle in which the package is secured so that its position remains fixed and there are no loading or unloading operations between the beginning and end of transportation. 12   In this case, the normal occupational dose limits apply (see Table 3.10).

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Going the Distance? The Safe Transport of Spent Nuclear Fuel and High-Level Radioactive Waste in the United States FIGURE 3.3 Graphical illustration of the radiation dose comparisons shown in Table 3.10. The dose data are plotted on a logarithmic scale to better illustrate the spread of values. Doses shown in the figure are annual limits (for standards and regulations) or exposures except for medical procedures and round-trip airline flights, which are one-time exposures. Black bars depict doses to workers or residents for the Yucca Mountain (YM) transportation program (SS = service station). uncontrollable risk. In principle, people do have some control over the background dose they receive based on where they choose to live. In practice, however, the great majority of people probably do not explicitly include radiation dose considerations in decisions about where to live. Most people probably do not even know the average background radiation dose in their current location of residence. Similarly, the radiation received by members of the public from a Yucca Mountain transportation program is also frequently viewed as involuntary and uncontrollable. Again, this is not completely true in principle; people have some control based on where they choose to live. In practice, however, it would be very difficult to make such a choice, given that transportation routes and schedules have not been established by DOE (see Chapter 5). There is also a qualitative difference between natural background radiation and radiation from a Yucca Mountain transportation program. The former is natural, whereas the latter is the result of human activities. Although exposures to radiation from these two sources have identical bio-

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Going the Distance? The Safe Transport of Spent Nuclear Fuel and High-Level Radioactive Waste in the United States logical effects on living organisms, the committee recognizes that some people may view the acceptability of these exposures differently given their different origins. Under the linear no-threshold risk model, background doses would be expected to elevate the risk of a fatal cancer.49 The use of background radiation in risk comparisons has been criticized by some (e.g., MacGregor et al., 2002a,b) because it implicitly suggests that anthropogenic exposures of the same magnitude as background radiation are acceptable to society and it does not address the possible effects of cumulative exposures. The committee uses natural background radiation to give interested readers an established benchmark for making comparisons and makes no value judgments about the acceptability of doses at background levels. Table 3.10 and Figure 3.3 also present the radiation doses received from a small number of common medical treatments. Comparisons using medical diagnostic procedures might be viewed by some people as inappropriate because the circumstances under which they are received are qualitatively different from spent fuel and high-level waste transportation: medical diagnostic procedures are voluntary and familiar and are widely perceived as having positive health benefits. The committee acknowledges these differences, but nevertheless decided to use medical procedures in its comparisons precisely because they would be familiar to many readers. The committee selected medical diagnostic procedures that represent relatively high, medium, and low radiation exposures to aid readers in making comparisons. The entries in Table 3.10 and Figure 3.3 are arranged from high to low dose to provide a visual comparative ranking. This “risk ladder” is commonly used to display comparative information (Covello et al., 1989). Several noteworthy observations can be made. First, according to analyses presented in the final Yucca Mountain EIS (DOE, 2002a), maximally exposed workers (primarily transportation crews, escorts, and inspectors) for the Yucca Mountain transportation program (first column in Table 3.10) are assumed to receive annual doses at the limits of the current international standards and DOE administrative limits shown in the second column of the table. The final EIS (DOE, 2002a, p. 6-43) notes that “individual crew members who operated legal weight trucks and escorts for rail shipments could be exposed to as much as 48 rem over 24 years of operation (maximum exposure of 2 rem each year).” In practice, this probably means that DOE will monitor worker doses to ensure that they do not exceed these limits. These exposures will be about seven times higher than average annual natural background radiation doses and about twice as high as the dose received in a whole-body CT (computed tomography) scan. 49   However, epidemiologic studies have not observed an association between background exposures and latent cancer incidence or fatalities.

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Going the Distance? The Safe Transport of Spent Nuclear Fuel and High-Level Radioactive Waste in the United States According to the final EIS, under the mostly truck scenario, the maximally exposed service station worker could receive a dose of about 1.3 mSv (130 mrem) per year, which would exceed current allowable dose limits to members of the public of 1.0 mSv (100 mrem) per year from all anthropogenic, nonmedical sources. The final Yucca Mountain EIS (DOE, 2002a, p. 6-40) notes that measures would be taken to keep this dose at or below the 1.0 mSv (100 mrem) limit. It should be noted that this worker dose estimate is very conservative: it assumes that every spent fuel and high-level waste truck shipment bound for Yucca Mountain stops at the service station during the 1800 hours the worker is on duty each year for 24 years. Maximally exposed members of the public are estimated to receive substantially lower annual radiation doses from a Yucca Mountain transportation program as shown by the two bottom-most entries in the first column of the table. The maximally exposed resident near a rail stop (for the mostly rail scenario) would receive an annual dose of about 0.12 mSv (12 mrem). This is roughly equivalent to the dose from about one chest X-ray or one round-trip airline flight between New York and Tokyo. The maximally exposed resident near a rail route (again for the mostly rail scenario) would receive about 0.0007 mSv (0.07 mrem), which is about 6 percent of the dose received in an X-ray to a human extremity (e.g., hand or foot). 3.3.2 Transport Accident Risks Given the robust construction of spent fuel transportation packages and the rigorous regulatory requirements for transporting them (Chapter 2), significant releases of radioactive material are very unlikely except possibly in extreme accidents, as indicated by the studies in Section 3.1.2. The final Yucca Mountain EIS estimates that the probability of such accidents is very low: 2.3 in 10 million per year for trucks to 2.8 in 10 million per year for trains (Table 3.8). This EIS also estimates exposures from releases in such accidents (Table 3.8): Estimated exposures in a maximally reasonably foreseeable accident would range from about 1100 person-rem for truck accidents to 9900 person-rem for train accidents. The maximally exposed individual is estimated to receive between 3 and 29 rem of radiation, which would be insufficient to cause acute radiation sickness or death. This exposure is estimated to produce between 0.5 and 5 latent cancer fatalities. The committee provides a comparison of the potential consequences of extreme accidents involving spent fuel transportation packages with those for other types of hazardous materials transport using cumulative complementary distribution functions. The construction of these functions for accidents involving a loaded spent fuel package is described in Section 3.1.2.

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Going the Distance? The Safe Transport of Spent Nuclear Fuel and High-Level Radioactive Waste in the United States For this comparison, the committee used the mean CCDF for accidents involving rail transport of PWR spent fuel that was analyzed in the reexamination study (Sprung et al., 2000) and is shown in Figure 3.2. The committee compared this mean CCDF to those for accidents involving rail transport of three other kinds of hazardous materials: a flammable liquid (methanol), a flammable gas (propane), and a toxic gas (chlorine). These materials were selected because they behave differently under accident conditions and produce a wide range of consequences. The CCDFs for these hazardous materials were estimated using a computer model that was designed to study the risks of hazardous materials shipments by rail.50 The model was a joint effort of the Chemical Manufacturers Association (now the American Chemistry Council), the Association of American Railroads, and the Railway Progress Institute. The model was designed to be used by the participating associations and their member companies to evaluate changes to rail hazardous material transportation equipment, routings, and operating practices and to evaluate the effectiveness of options for reducing the risk of accident-caused hazardous material releases from tank cars through such changes. The model has not been published in the open literature, but it was peer reviewed during its development. The overall model has two main components: A frequency submodel that provides an estimate of the probability of occurrence and size of a release as a function of railroad operating factors (e.g., speed, track class) and tank car type A consequence submodel that provides estimates of the consequences of a release of a defined volume of a specific chemical for human and/or environmental impact51 The model also has an extensive database that contains accident rates, benefits of risk reduction options, release probabilities, ignition probabilities, spill size distributions, basic sets of weather conditions, chemical properties for eight preselected materials, and other information needed to run the model. The eight materials included in the model are acetaldehyde, ammonia, chlorine, ethylene oxide, methanol, propane, sodium hydroxide, and styrene. 50   Inter-Industry Rail Safety Task Force’s Detailed Rail Model, Version 2.0, 1996. 51   SuperChems™ is the consequence modeling package used within the model to generate the hazard zones for potential human impacts.

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Going the Distance? The Safe Transport of Spent Nuclear Fuel and High-Level Radioactive Waste in the United States The model is designed to run “projects.” A project is defined by A hazardous material of interest, A designated type of railcar, A specified number of trips (trains) of interest, and A route, which includes information on length, track class, train speed, train length, number of hazardous material cars of interest per train, population density (for human impact) and/or soil type (for environmental impact). Each route is generally subdivided into pieces, called segments, within which the variables listed above are essentially constant. This model was used to calculate CCDFs for a single railcar carrying 20,000 gallons of three types of hazardous materials (chlorine, propane, and methanol) being transported in a general train with typical train speeds, track conditions, and train lengths. The number of shipments (100), the route lengths (about 1600 miles), and the population densities along the shipping routes were approximately the same for these three types of hazardous material shipments and the spent fuel shipments. The results should not be taken as exact estimates, but they are useful for comparison purposes. The results of the calculations are plotted in Figure 3.4. The horizontal axis represents the number of expected fatalities from an accident having an annual frequency shown on the vertical axis. The CCDF for spent fuel shown on the figure was plotted by multiplying the mean CCDF curve shown in Figure 3.2 by a nominal probability coefficient of 5.75 × 10−2 fatal cancer per sievert (5.75 × 10−4 fatal cancer per rem)52 (EPA, 1998b, Table 7.3). Several features of this plot are noteworthy: First, the mean CCDF for chlorine has a relatively flat shape and has the highest accident frequencies and fatalities of the four cases examined. Chlorine gas is highly toxic and can be fatal if inhaled. Once released, gas can be dispersed widely by wind and can have adverse consequences even at relatively low concentrations. Thus, accidental releases can have adverse consequences even in lightly populated areas and can produce many casualties in densely populated areas. Accidental releases of flammable gases such as propane can have similar consequences to toxic gas releases, but the expected number of fatalities is lower. The primary consequence of concern in a flammable gas release is an explosion or large fire. This requires an ignition source to be present when the proper fuel-air mixture is attained following the accident. The 52   For low-dose, low linear energy transfer radiation, assuming uniform irradiation of the body. This nominal probability coefficient is age and gender averaged.

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Going the Distance? The Safe Transport of Spent Nuclear Fuel and High-Level Radioactive Waste in the United States FIGURE 3.4 Complementary cumulative distribution functions showing expected fatalities from hypothesized accidents during transport of three types of hazardous materials and spent fuel. Calculations are explained in the text. consequences of an explosion or fire will be more localized than a toxic gas release; hence, the expected fatalities from accidental releases are lower. Accidental releases of flammable liquids such as methanol would be expected to have even fewer consequences. These consequences will generally be more localized to the area of the spill, and not all releases will yield fatalities. The mean CCDF is truncated at about three fatalities due to these localized effects. The mean CCDF for accidental releases of radioactive material from spent fuel packages has the same general shape as the CCDF for propane. However, the frequency of accidents that lead to such releases is expected to be four to five orders of magnitude lower because of the robust construction of the transportation packages. Figure 3.4 shows that on a comparative basis, the likelihood of extreme accidents that would lead to fatalities is several orders of magnitude lower for spent fuel than for the other hazardous materials shown in the figure. In Section 3.1.2, the committee notes

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Going the Distance? The Safe Transport of Spent Nuclear Fuel and High-Level Radioactive Waste in the United States that the risk estimates provided in the reexamination study (Sprung et al., 2000) from which this CCDF was taken are likely to be neither realistic nor bounding and may overestimate the risks. In other words, the risk estimates for accidents involving spent fuel shown in Figure 3.4 may be higher than is actually the case. 3.4 TRANSPORTATION RISKS: FINDINGS AND RECOMMENDATIONS The committee concludes this chapter with findings and recommendations in response to the first three charges of its original statement of task shown in Sidebar 1.1: FINDING: There are two potential sources of radiological exposures from transporting spent fuel and high-level waste: (1) radiation shine from spent fuel and high-level waste transport packages under normal transport conditions; and (2) potential increases in radiation shine and release of radioactive materials from transport packages under accident conditions that are severe enough to compromise fuel element and package integrity. The radiological risks associated with the transportation of spent fuel and high-level waste are well understood and are generally low, with the possible exception of risks from releases in extreme accidents involving very long duration, fully engulfing fires. While the likelihood of such extreme accidents appears to be very small, their occurrence cannot be ruled out based on historical accident data for other types of hazardous material shipments. However, the likelihood of occurrence and consequences can be reduced further through relatively simple operational controls and restrictions and route-specific analyses to identify and mitigate hazards that could lead to such accidents. RECOMMENDATION: Transportation planners and managers should undertake detailed surveys of transportation routes to identify potential hazards that could lead to or exacerbate extreme accidents involving very long duration, fully engulfing fires. Planners and managers should also take steps to avoid or mitigate such hazards before the commencement of shipments or shipping campaigns. (See also the recommendation to transportation regulators in Chapter 2 on operational controls and restrictions on spent fuel and high-level waste shipments to reduce the chances that such hazards might be encountered in actual service.) The finding that “radiological risks … are well understood and are generally low” is based on a large set of observational data and studies described in this chapter and in Chapter 2. These include the following:

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Going the Distance? The Safe Transport of Spent Nuclear Fuel and High-Level Radioactive Waste in the United States Rigorous international standards and U.S. regulations for the design, construction, testing, and quality assurance of spent fuel packages, including the built-in safety margin requirements for package designs (see Chapter 2); and more than four decades of worldwide experience in transporting spent fuel (Section 3.1). Although there have been accidents and incidents, to the committee’s knowledge there has never been a large-scale release of radioactive materials reported from the failure of a spent fuel package during an accident. The broad sharing of information on experiences and best practices by transportation planners, implementers, and regulators through organizations such as the IAEA promotes the continued maintenance of this safety record. Full-scale crash testing of transport packages under severe accident conditions (Section 2.3). These tests show that properly constructed spent fuel packages can withstand severe accidents without a loss of containment that would result in releases of radioactive material that exceed regulatory limits. These tests also illustrate that the regulatory requirements for spent fuel packages (e.g., free-drop tests) produce in many cases more severe tests of package integrity than do severe accidents. A series of increasingly sophisticated analytical and computer modeling studies of spent fuel transport package performance (Section 3.1.2). The most recent of these studies (Sprung et al., 2000; DOE, 2002a) have attempted to estimate risks using actual spent fuel transport package, fuel, route, and severe accident characteristics and generally conservative assumptions and models. Other studies that examine the mechanical and thermal loading conditions from severe accidents that did not involve spent fuel transport (Section 2.2.3). These studies have shown that with the possible exception of very long duration fires, the loading conditions from these accidents would not have exceeded regulatory limits. Of course, spent fuel transportation is not risk-free, and past experience is not necessarily a useful predictor of future performance. The fact that spent fuel transportation risks have been low in the past does not necessarily mean that risks will also be low in the future. Future risks depend on a number of factors including the quantities and ages of spent fuel transported, associated scaling issues related to the overall size of the transport program, transport modes, and the care taken in fabricating and maintaining transport packages and executing transportation operations. Ongoing vigilance by regulators and shippers will be essential for maintaining low-risk programs in the future, especially for the scale-up and operation of large-quantity shipping programs. Any accident or terrorist attack that results in the large-scale release of radioactive material into the environment would likely have worldwide implications and could result in a

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Going the Distance? The Safe Transport of Spent Nuclear Fuel and High-Level Radioactive Waste in the United States temporary or even permanent halt to ongoing transportation programs for spent fuel in the United States. The recommendation calls for transportation implementers to survey the routes they plan to use for spent fuel and high-level waste to identify hazards that could lead to very long duration fires. This recommendation arises from the finding in Chapter 2 that very long duration, fully engulfing fires might produce thermal loading conditions sufficient to compromise package containment effectiveness. The recommended survey would involve traveling the route in advance of a shipment (or shipping campaign if several shipments are planned) to identify Facilities close to the route that use or store large quantities of flammable materials (e.g., refineries, petroleum and gas storage tanks); Large-volume flammable hazardous material shipments along the routes to be used; and Other route conditions (e.g., the presence of multitrack tunnels, bridges, rail yards, and sidings, as well as remote locations) that could make it difficult to deploy an effective firefighting capability. Once these conditions have been identified, implementers can take steps to avoid or mitigate these hazards. For example, routes can be altered to avoid multitrack train tunnels, and time spent in rail yards and sidings, where packages could be exposed to other trains carrying large amounts of flammable materials, can be minimized. Where such hazards cannot be avoided completely, shipments can be scheduled to minimize encounters with other hazardous materials trains, or emergency response preparedness can be improved along specific route segments of concern. The committee judges that none of these recommended survey and mitigation actions would be difficult or expensive to implement. Transportation implementers and regulatory authorities now routinely survey routes to identify other safety and security concerns prior to shipping spent fuel. This recommended action simply represents an expansion of an activity that many implementers already carry out on a routine basis. FINDING: The social risks for spent fuel and high-level waste transportation pose important challenges to the successful implementation of programs for transporting spent fuel and high-level waste in the United States. Such risks, which can result in lower property values along transportation routes, reductions in tourism, and increased anxiety, have received substantially less attention than health and safety risks, and some are difficult to characterize. Current research and practice suggest that transportation planners and managers can take early proactive steps to characterize, communicate, and manage the social risks that arise from their operations. Such

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Going the Distance? The Safe Transport of Spent Nuclear Fuel and High-Level Radioactive Waste in the United States steps may have additional benefits: they may increase the openness and transparency of transportation planning and programs; build community capacity to mitigate these risks; and possibly increase trust and confidence in transportation programs. RECOMMENDATION: Transportation implementers should take early and proactive steps to establish formal mechanisms for gathering high-quality and diverse advice about social risks and their management on an ongoing basis. The committee makes two recommendations for the establishment of such mechanisms for the Department of Energy’s program to transport spent fuel and high-level waste to a federal repository at Yucca Mountain: (1) expand the membership and scope of an existing advisory group (Transportation External Coordination [TEC] Working Group; see Chapter 5) to obtain outside advice on social risk, including impacts and management; and (2) establish a transportation risk advisory group that is explicitly designed to provide advice on characterizing, communicating, and mitigating the social, security, and health and safety risks that arise from the transportation of spent fuel and high-level waste to a federal repository or interim storage. This group should be comprised of risk experts and practitioners drawn from the relevant technical and social science disciplines and should be convened under the Federal Advisory Committee Act or a similar arrangement to enhance the openness of its operations. Its members should receive security clearances to facilitate access to appropriate transportation security information. The existing federal Nuclear Waste Technical Review Board, which will cease operations no later than one year after the Department of Energy begins disposal of spent fuel or high-level waste in a repository, could be broadened to serve this function. This finding and recommendation spring from several factors: Social risk is a poorly understood phenomenon; expert opinion frequently differs; DOE does not, to the committee’s knowledge, have any precedent to guide its understanding and management of social risks; and most transportation program staff are not likely to be well acquainted with either theory or practice on this issue. Consequently, the committee concluded that broad input and advice on social risks will be essential to the establishment and ultimate success of programs to transport spent fuel and high-level waste to a federal repository or interim storage. The recommendation represents pragmatic steps that transportation implementers can take immediately and at relatively low cost to better understand and (working with affected communities) manage the social risks from their programs. These groups are not intended to undertake research on risk. Instead, the committee intends that they have a practical, problem-solving focus and be committed to working closely with program

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Going the Distance? The Safe Transport of Spent Nuclear Fuel and High-Level Radioactive Waste in the United States staff to help it become more effective in carrying out the program’s mission. One of the most important functions of these advisory groups would be to foster continuous learning and improvement. The recommendation to expand the scope and membership of the TEC Working Group builds on and complements existing public participation and communication activities within DOE’s transportation program for Yucca Mountain. The TEC Working Group is now comprised of state, tribal, local, and industry representatives, and it provides a conduit for communication and advice on topics such as emergency response, inspection and enforcement, training, and public information. The committee recommends that the membership of TEC be expanded to include social risk experts and representative stakeholders from affected communities to provide information on social risks of DOE’s transportation operations and their management. The committee also recommends the establishment of a separate transportation risk advisory group that would advise DOE on characterizing, communicating, and mitigating the social, security, and health and safety risks to communities near transportation routes. The suggestion that the Nuclear Waste Technical Review Board could be broadened to serve this function is intended to take advantage of an established capability within the federal government. This group is independent of DOE and its membership is drawn from the scientific and technical communities. The procedures for nominating and appointing members to this board (i.e., presidential appointments based on nominations by the National Academy of Sciences) are designed to ensure that it is balanced and credible to carry out its mission. Finally, although this recommendation is focused primarily on DOE, it also applies to any large-quantity shipping program, including the program to ship commercial spent fuel to centralized interim storage (e.g., Private Fuel Storage, LLC, in Utah).