Characterization of Remote-Handled Transuranic Waste for the Waste Isolation Pilot Plant: Final Report (2002)

The Department of Energy’s (DOE’s) Carlsbad Field Office asked the National Research Council to review a proposed characterization plan for remote-handled transuranic (RH-TRU)¹ waste and to provide recommendations, as necessary, for improving the plan’s technical soundness, protection of worker safety and health, and compliance with regulatory requirements.

There are approximately 3,800 cubic meters of defense-related RH-TRU waste to be removed from DOE’s weapons complex. DOE is seeking authorization to dispose of this RH-TRU waste in the Waste Isolation Pilot Plant (WIPP), a geologic repository in southeastern New Mexico. WIPP is regulated by the Environmental Protection Agency (EPA) and the New Mexico Environment Department (NMED).

WIPP is currently certified by the EPA and permitted by the NMED to dispose only of contact-handled (CH) and mixed² CH-TRU waste. To obtain authorization to ship RH-TRU waste to WIPP, DOE must submit to the regulatory agencies a characterization plan for RH-TRU waste and request a modification of the EPA Certification and RCRA Permit. The regulatory agencies may accept, reject, or propose modifications to the characterization plan and, eventually, may authorize RH-TRU waste disposal in WIPP.

Remote-handled TRU waste presents a long-term (i.e., 10,000 years) radiological hazard associated with TRU radionuclides (related to the presence of long-lived alpha-emitting isotopes) and a short-term (less than 300 years) radiological hazard associated with short-lived gamma-emitting radionuclides (related to the presence of fission and activation products). Gamma radiation can penetrate through the walls of waste containers and the skin; therefore, RH-TRU waste presents a potential for radiation doses to workers during waste characterization, handling, and emplacement. The associated costs due to the heavy shielding and remote-handling equipment, necessary to protect workers from radiation, are also significant. The long-term radiological hazard of RH-TRU waste is associated with the potential for TRU radionuclide release into the environment once the waste is disposed of in WIPP.

While RH-TRU waste volume represents a small fraction of the allowed TRU waste in WIPP (3,800 cubic meters out of approximately 176,000 cubic meters), it accounts for

14 percent of the total curie activity in DOE’s TRU inventory. However, the number of TRU (i.e., from alpha-emitting radionuclides with a half-life greater than 20 years) curies in the RH-TRU waste inventory is 2 orders of magnitude lower than that in the CH-TRU waste inventory expected in WIPP. Also, most of the total (CH plus RH) long-term (i.e., TRU) activity expected in WIPP comes from CH-TRU waste, with only a 0.5 percent contribution from RH-TRU waste (see Table 2.3 in Chapter 2).

Remote-handled TRU waste to be emplaced in WIPP is stored or is to be generated as the result of cleanup activities at 13 DOE weapons complex sites (see Chapter 2). Approximately 1,600 cubic meters of projected RH-TRU waste is waste that originates from the dismantlement of hot cells and other facilities used for defense-related purposes, waste that must be recovered and separated from other wastes (such as at the Hanford Site), or waste that must be reprocessed to eliminate hazardous components prohibited in WIPP (such as at Oak Ridge National Laboratory). Already stored at DOE sites are approximately 2,200 cubic meters of RH-TRU waste, but most of this inventory must be characterized and repackaged to meet waste transportation criteria. Only 5 percent of the waste has been characterized and packaged in a form that could be suitable for shipment to WIPP. To obtain authorization to ship RH-TRU waste to WIPP, generator sites must characterize all their RH-TRU waste inventories according to a plan approved by EPA and NMED.

Congress designated WIPP as the nation’s defense-related transuranic waste repository in the Land Withdrawal Act of 1992. This Act allows the geologic disposal in WIPP of up to 175,564 cubic meters of TRU waste, including 7,080 cubic meters (4 percent of the total volume) of RH-TRU waste. The EPA, under this Act, regulates the radiological release limits for WIPP over a period of 10,000 years. The NMED, under RCRA, regulates the non-radiological risks related to hazardous waste disposal during the operational phase and up to 30 years following repository closure.

The EPA Certification and RCRA Permit establish characterization requirements for all TRU waste (CH and RH) to be emplaced in WIPP. Contact-handled TRU waste is characterized according to a plan that was negotiated for almost two decades among DOE and the regulators prior to the certification of the WIPP facility. This plan consists of 100 percent confirmation of acceptable knowledge (AK)³ information through visual examination, radioassay, headspace gas sampling, or radiography. A DOE review of the CH-TRU waste characterization procedures revealed that DOE developed self-imposed waste restrictions in the waste acceptance criteria and in the implementation documents used by generator sites to characterize CH-TRU waste. A previous National Research Council committee found that these self-imposed procedures lack technical, safety, or legal basis (see Sidebar 3.1). DOE is now facing the challenge of proposing a characterization plan for RH-TRU waste that meets EPA and NMED requirements but follows a different approach than that used for CH-TRU waste.

The following two documents include DOE’s proposed characterization plan for RH-TRU waste:

• Document 1: Notification of Proposed Change to the EPA Title 40 CFR Part 194 Certification of the WIPP.

• Document 2: Request for RCRA Class 3 Permit Modification to the NMED.

On June 28, 2002 DOE submitted Documents 1 and 2 to EPA and NMED, respectively. The committee reviewed two drafts of the above documents prior to their submission. Findings and recommendations in this report apply to the characterization plan as presented in the March 2002 draft.

DOE’s goal is to adopt a performance-based approach to meet EPA and NMED requirements for waste characterization. This approach relies on the impact of the RH-TRU waste inventory on the performance of WIPP. The Sandia National Laboratories undertook two performance assessment analyses showing that the characteristics of RH-TRU waste will have a negligible impact on the potential long-term release of radionuclides into the environment. This is due to the characteristics of DOE’s RH-TRU waste inventories in terms of volume and radiological composition.

To address the EPA and NMED regulatory requirements, DOE proposes to use the following characterization methods: dose-to-curie conversion, visual examination, radiography, direct assay, counting containers, AK, and characterization at the time of packaging. The dose-to-curie method consists of correlating a surface dose rate measurement with documented waste isotopic distributions through the use of empirically developed conversion factors. Visual examination involves the removal of items from the container (by remote-handled methods) for inspection and identification. Visual examination does not provide information on the isotopic composition of waste. Radiography utilizes penetrating radiation (typically X-rays) to investigate the contents of containers. Direct assay consists of radiochemical analyses using the same methods approved for CH-TRU waste characterization. Counting containers is the method used to determine the amount of metal emplaced in WIPP by an automatic inventory of the number of containers during packaging. Characterization at the time of packaging consists of visual examination and the use of other characterization methods (i.e., AK, radiochemical analysis, or radiography) as waste is generated, packaged, or repackaged in a form suitable for shipment to WIPP. The AK method, which is the primary method of compliance for waste characterization, consists of collecting historical information and new information obtained through the “characterization at the time of packaging” method (see Finding 1B below). Further details are provided in Chapter 4.

Unlike the current CH-TRU waste characterization approach, which requires 100 percent confirmation of the AK information, for RH-TRU waste characterization DOE proposes performing confirmatory measurements only on 10 percent of the waste. This confirmation activity is proposed when AK is insufficient to address a characterization requirement.

This report is not meant to be a comprehensive review of the entire RH-TRU waste program, which encompasses RH-TRU waste transportation, storage, waste

certification, operational safety issues, occupational health and safety regulations, waste generator states’ regulations, waste acceptance criteria, as well as DOE orders.

The committee used the criteria listed in the statement of task to assess DOE’s proposed characterization plan (see Sidebar P.1 in the Preface). Findings and recommendations address: 1) the context of RH-TRU waste characterization, 2) the characterization plan’s technical soundness, 3) protection of worker safety and health, and 4) compliance with regulatory requirements. Findings are referenced (in parentheses) according to the order they are presented in Chapter 5. Each finding is followed by the corresponding recommendation (in bold characters). The rationales are provided in Chapter 5.

1) Context of RH-TRU Waste Characterization

The committee did not verify the data provided by DOE on its RH-TRU waste inventories. Acknowledging the past fluctuations of RH-TRU waste inventories, the committee assumes that DOE presented the most up-to-date information available. Even if the information presented in DOE inventories were not accurate, by law the RH-TRU waste emplaced in WIPP cannot exceed 4 percent of the total volume inventory and 5.1 million curies. According to DOE inventories, 95 percent of the RH-TRU waste to be disposed of in WIPP has yet to be generated or needs to be processed, packaged, or repackaged. This waste will be characterized (through visual examination and physical and chemical analyses) at the time of packaging (Finding 1A). DOE should emphasize the argument that the characterization information collected for most of RH-TRU waste does not need confirmatory measurements because the repackaging or generation of waste will be carried out under a certified quality assurance program. If the volume of RH-TRU waste represents between 2 and 4 percent of the volume of TRU waste, and the information collected for over 95 percent of RH-TRU waste does not need confirmation, then only the remaining 5 percent of the RH-TRU waste inventory (between 0.1 and 0.2 percent of the total inventory) needs confirmatory activities.

As previously mentioned, DOE uses the term “AK” to indicate both the historical information and the newly generated characterization information collected at the time of waste generation, packaging, or repackaging. However, for 95 percent of the RH-TRU waste inventory, AK refers mostly to the latter (Finding 1B). The committee recommends that DOE use a different term than “AK” for this newly generated information. Using AK for both historical and newly generated information is potentially confusing because AK is generally associated with historical information, which requires some type of confirmation.

2) Characterization Plan’s Technical Soundness

The committee found that DOE’s proposed characterization plan is not completely performance based and that several characterization activities are based on non-technical considerations (Finding 2A). The committee questions the technical basis of some of these characterization activities. The committee acknowledges that non-technical considerations may be important for maintaining effective working relationships among DOE, EPA, and NMED; however, DOE should propose only characterization activities that have a technical, health and safety, or regulatory basis.

The committee provides the following examples of activities lacking a technical basis in the context of RH-TRU waste characterization: determination of radiological activity, free water/liquid, ferrous metal, cellulosics, plastic, rubber, and polychlorinated biphenyls

content. According to the Sandia impact analyses, these RH-TRU waste parameters will have only a negligible impact on the performance of the repository. Also, DOE did not provide the technical basis for selecting 10 percent of the waste as a representative waste sample to perform confirmation activities.

In some instances, the plan lacked specificity because most of the operational details are site-specific and were not available at the time of writing (Finding 2B). It is the committee’s understanding that, along with Documents 1 and 2, DOE will submit three site-specific documents containing a completed characterization plan for selected RH-TRU generator sites. The committee supports this initiative. The site-specific documents should present clear and technically defensible data qualification requirements for RH-TRU waste characterization.

Also, tolerable decision error rates are never clearly defined in Documents 1 and 2 (Finding 2C). Tolerable decision error rates are determined by weighing the consequences of mischaracterization against the costs (including worker risks) of achieving better characterization. Once established, tolerable decision error rates can be used to identify the attendant quality assurance requirements for sampling (i.e., the measurement quality objectives, which DOE calls quality assurance objectives⁴). DOE’s proposed characterization plan should address tolerable decision error rates associated with characterization information. These errors should not be overly stringent so as to negatively impact the sites’ ability to implement ALARA.⁵

For the 5 percent of the RH-TRU waste inventory that does not require packaging or repackaging, it is not clear how visual examination and radiography can confirm AK information for prohibited items (Finding 2D). For example, visual examination and radiography cannot distinguish between corrosive and non-corrosive liquids, whereas AK may provide records of the existence of such liquids in the waste. Historical AK may be a better indicator of some of the currently prohibited items than visual examination and radiography. The characterization plan should clarify under which conditions confirmation of historical AK is warranted and what are the most effective methods proposed. The committee could not determine the effectiveness of specific technologies, such as X-ray radiography, in providing confirmatory data for the high-dose-rate fraction of RH-TRU waste containers (Finding 2E). DOE should provide justification for the technologies proposed for obtaining confirmatory data and provide evidence of their effectiveness across the entire spectrum of dose rates for RH-TRU waste.

Overall, in the context of RH-TRU waste characterization and from a performance point of view, the committee found that the general approach DOE is proposing is technically sound. However, Documents 1 and 2 do not present a performance-based plan as effectively as they could.

3) Protection of Worker Safety and Health

Potential worker radiation doses and related characterization costs are distinguishing features of RH-TRU waste compared to CH-TRU waste, but estimates of worker doses and characterization costs for RH-TRU waste are limited, site-specific, and not completely reliable (Finding 3A). DOE could strengthen the rationale of its

characterization plan for RH-TRU waste by including a discussion of estimates of worker doses and characterization costs in the three site-specific plans accompanying the submittal documents. Discussion of worker doses and costs is relevant since radiation protection standards and criteria are predicated on the concept of assessing the decrement in risk per increment in cost. It is also important to recognize that tolerable decision error rates associated with characterization methods will have an impact on the implementation of the ALARA principle at generator sites (see Finding 2C).

Documents 1 and 2 provide flexibility to the generator sites in the implementation of the RH-TRU waste characterization plan (Finding 3B). DOE should continue its effort in ensuring sufficient flexibility to generator sites in the implementation of the characterization plan. However, characterization activities that share common elements across sites should be standardized. Given the differences among generator sites (for instance, in the composition of waste streams, quality of AK and inventories, and characterization and repackaging facilities), flexibility in a waste characterization plan is important to adapt the sites’ implementation programs. A rigid, overly prescriptive characterization plan may lead to unnecessary radiation doses to workers and characterization costs. However, standardization of common elements of the characterization program may facilitate characterization compliance verifications and, possibly, reduce characterization costs.

4) Compliance with Regulatory Requirements

The difficulty of this latter part of the statement of task lies in performing a review of a characterization plan for RH-TRU waste against compliance with existing characterization requirements that currently exclude RH-TRU waste. The task is further complicated by the existence of the characterization approach approved by EPA and NMED that is currently used for CH-TRU waste. It is important to emphasize the difference between regulatory requirements and the approach to meet such requirements. While the regulatory requirements for CH- and RH-TRU waste characterization are the same, the approach to address these requirements can be different. The committee evaluated, from a technical point of view, the approach DOE is proposing to characterize RH-TRU waste and how it addresses regulatory requirements. The committee was not asked to comment on these requirements nor was it asked to determine if the plan complies with the regulatory requirements. The latter is obviously a policy decision belonging to the regulatory agencies.

The committee found that DOE’s proposed characterization plan for RH-TRU waste deliberately tracks the characterization plan for CH-TRU waste (Finding 4A). The committee recommends that DOE evaluate whether existing characterization practices for CH-TRU waste, when applied to the characterization of RH-TRU waste, have an impact on the protection of the environment, health and safety of public and workers, and cost-effectiveness of the characterization program. Also, like in the CH-TRU waste characterization plan, Documents 1 and 2 include, as basis for characterization objectives, requirements other than those applicable to EPA certification and RCRA permit, for instance transportation requirements or waste acceptance criteria (Finding 4B). The committee recommends that submittal documents focus on regulatory requirements under the relevant agency’s purview and distinguish between these requirements and ancillary information describing the context of RH-TRU waste characterization. While it is important to provide, in the submittal documents, the full context of the characterization of RH-TRU waste, including material outside the regulatory jurisdiction of EPA and NMED may unnecessarily complicate the

regulatory review process. It would be helpful for both DOE and the regulatory agencies if the submittal documents indicate which requirements are to be reviewed and which are given for information purposes. This would allow the regulator and DOE to keep track of various requirements and to streamline characterization practices as experience is gained.

The committee observed a net improvement between the July 2001 and March 2002 drafts of the characterization plan. Concerning the plan’s technical soundness, DOE itself recognized that this plan is not completely performance based and that other considerations played a role in its development. The committee identified some characterization activities lacking technical bases in the context of RH-TRU waste and a potential technical problem with radiographic examination of waste. Also, DOE’s proposed characterization plan does not adequately address the issue of tolerable decision error rates associated with all characterization information.

In some instances, the plan lacks specificity because most of the operational details are site-specific and were not available at the time of writing. The site-specific accompanying documents should provide useful clarifications. In the context of RH-TRU waste characterization and from a performance point of view, the committee found that the general approach DOE is proposing is technically sound. However, Documents 1 and 2 do not present a performance-based plan as effectively as they could.

Concerning the plan’s protection of worker health and safety, the committee recommends that the approved characterization plan not include overly stringent tolerable decision error rates that could negatively impact the sites’ ability to manage worker risks. It is important to recognize that the allowable uncertainties in the final characterization plan approved by EPA and NMED may have an impact on generator sites’ radiation protection programs.

Concerning compliance with regulatory requirements in the EPA Certification and RCRA Permit, the committee did not observe any requirement that was not addressed in DOE’s characterization plan. In fact, the proposed characterization plan for RH-TRU waste addresses some requirements that are not under the relevant agency’s purview. Moreover, the characterization plan for RH-TRU waste deliberately tracks that for CH-TRU waste. The committee recommends evaluating whether existing characterization practices for CH-TRU waste, when applied to the characterization of RH-TRU waste, have an impact on the protection of the environment, health and safety of public and workers, and cost-effectiveness of the characterization program.