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OCR for page 183
9
Other Guidances for TENORM
This chapter reviews guidances for TENORM other than indoor radon
that have been developed by organizations other than the Environmental
Protection Agency (EPA). Guidances for TENORM developed by EPA,
including the guidance for indoor radon, are discussed in chapter 7, and
guidances for indoor radon developed by EPA and other organizations are
discussed in chapter 8.
This chapter discusses guidances that are directly applicable, or
potentially relevant, to TENORM other than indoor radon that have been
developed by the National Council on Radiation Protection and Measurements,
the International Commission on Radiological Protection, the Health Physics
Society, the Nuclear Regulatory Commission, the Department of Energy,
various state governments and the Conference of Radiation Control Program
Directors, the International Atomic Energy Agency, and the Commission of the
European Communities and other nations. The roles of these organizations in
radiation protection of the public and the regulation of TENORM are discussed
in chapter 6. This chapter also discusses the important issue of the transferability
of standards from one exposure situation to another.
NATIONAL COUNCIL ON RADIATION PROTECTION AND
MEASUREMENTS
National Council on Radiation Protection and Measurements (NCRP)
Report No. 116 (NCRP 1993a) contains NCRP's most recent recommendations
on limitation of exposure of workers and the public to ionizing radiation. For
human-made sources, the recommended annual dose limits for individual
members of the public are 1 mSv (100 mrem) for continuous exposures and 5
mSv (500 mrem) for infrequent exposures. Exposures of the public should be
183
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184
GUIDELINES FOR EXPOSURE TO TENORM
justified (no exposures without expectation of benefit) and should be "as low as
reasonably achievable" (ALARA). It is also recommended that if a single site
could potentially expose members of the public to more than 25% of the dose
limit, the operator should ensure that the annual dose from all human-made
sources does not exceed 1 mSv (100 mrem). This guidance is similar to the
federal guidance proposed by EPA, which is discussed in chapter 7, but it does
not apply to natural sources and, by extension, apparently not to TENORM.
NCRP recognizes that there are circumstances when natural
background itself, or more especially "natural radiation sources enhanced
locally by man's operations for selected purposes, can give rise (sometimes quite
inadvertently) to annual exposures above the level of 1 mSv. It then becomes
necessary to consider at what exposure level remedial action, which may only
be possible at substantial societal cost, should be undertaken. Remedial action
levels involve a balance of risk with many other socio-econornic factors."
Once a remedial action level is established, action is expected when a
level above it is found. NCRP recommends that, once a decision is made to take
remedial action, the action not be limited to reducing the dose to just below the
action level. Reduction to levels substantially below the remedial action level,
following the ALARA principle, might be obtainable and appropriate.
Most of the discussion on remedial action levels for natural sources in
NCRP Report No. 116 (NCRP 1993a) is focused on indoor radon for which an
action level of 7 x 10-3 Jh/m3 (2 WLM/y) is recommended. This action level is
recognized as 10 times the national average for indoor radon and appears to be
justified partly on the basis of feasibility, rather than attainment of an a priori
numerical risk limit.5 NCRP states that "a remedial action level must, therefore,
be chosen for which the greatest risks are avoided but the societal impacts are
not excessive" and NCRP goes on to state that "Therefore, NCRP has proposed
a remedial action level which is based on excess lifetime risk being no more
than ten times the excess lifetime risk associated with the average annual
background level found in homes that is 7.0 x 10-3 Jhlm3/y."
sAlthough it seems clear in NCRP Report No. 116 (NCRP 1993a) that the
remedial action level for indoor radon is justified as a multiple of 10 of the
average indoor radon level, and that societal effects are considered, a
predecessor report (NCRP 1984c) justifies the same limit on the basis of
numerical risk such that "an excess risk of death from lung cancer of 2% or
more over a lifetime for the individual exposed to elevated or enhanced levels of
radon daughters should be avoided."
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OTHER GUIDANCES FOR TENORM
185
For other natural sources, NCRP states "that in the case of other
exposure from natural radiation sources, considerations similar to those applied
to radon would appear to be reasonable. Since the average exposure to
individuals in the United States from natural radiation sources, excluding radon,
is approximately 1 mSv annually, it is recommended that remedial action be
undertaken when continuous exposures from natural sources, excluding radon,
are expected to exceed five times the average or 5 mSv (500 mrem) annually."
As in the case of radon, the 5-mSv action level appears to be justified, at least
partly, on the basis of feasibility rather than attainment of an a priori numerical
risk; lathe committee has assumed that this remedial action level is applicable
only to pre-existing situations for which remedial action is the only remedy, and
not to future practices.
It is important to note that the 5-mSv remedial action level is a total
dose (except of radon) from natural radiation, including naturally distributed
sources and any increases in natural radiation dose caused by human activities
(that is, TENORM). For example, in an area with a somewhat elevated
background of 1.5 mSv (excluding radon) from naturally distributed sources,
the recommended remedial action level would amount to 3.5 mSv for the
TENORM contribution.
INTERNATIONAL COMMISSION ON RADIOLOGICAL
PROTECTION
International Commission on Radiological Protection Publication 60
(ICRP 1991) contains the most recent ICRP recommendations on limitation of
exposure to ionizing radiation. As with NCRP Report No. 116 (NCRP 1993a),
recommendations are made for both workers and the public. Recommended
limits for the public are given for "practices which involve the intended release
of radioactivity to the environment from installations," but are explicitly
avoided for cases where intervention is the only possible remedy. ICRP uses
essentially the same principles of dose limitation as NCRP. Both require that
practices leading to increased dose be justified as being beneficial. NCRP uses
ALARA as a guiding principle, whereas ICRP uses the term "optimization" to
mean essentially the same thing. ICRP positions on limitation of dose to the
public are summarized below.
For "practices" that involve the intended release of radioactivity to the
environment from installations, ICRP recommends an annual dose limit for
individuals of 1 mSv (100 mrem). Radon in air and natural and artificial
radioactivity already present in the environment are specifically excluded from
this limit, which is the same as that recommended by NCRP.
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186
GUIDELINES FOR EXPOSURE TO TENORM
In some situations, the sources, pathways, and exposed people are
already in place when decisions about control measures are being considered.
Any new control procedures will commonly constitute intervention. ICRP states
that "An important group of such situations is that involving exposure to natural
radiation," so its recommendations concerning intervention appear to be
applicable to existing TENORM situations. However, the recommendations
concerning intervention are not applicable to decommissioning of licensed
operations involving naturally occurring radionuclides, such as the milling of
uranium ores (Clarke 1995~.
According to ICRP, intervention should be justified in the sense that it
does more good than harm; net benefit should be optimized. The dose limits for
the public recommended by ICRP are only for use in the control of practices.
The use of ICRP dose limits or other predetermined dose limits as the basis for
deciding on intervention might involve measures that would be out of
proportion to the benefit obtained and would thus conflict with the principle of
justification. ICRP recommends against the application of dose limits for
deciding on the need for, or scope of, intervention unless doses approach those
at which serious deterministic effects are caused.
For the case of radioactive residues from previous events, ICRP states
that "the need for and extent of remedial action has to be judged by comparing
the benefit of the reductions in dose with the detriment of the remedial work,
including that due to doses incurred in the remedial work."
HEALTH PHYSICS SOCIETY
The Health Physics Society (HPS), a US professional organization of
radiation-protection specialists, has issued policy statements on radiation dose
limits for the general public (HPS 1992) and radiation standards for site cleanup
and restoration (HPS 1993~. Several of the recommendations are directly
applicable to TENORM; others are indirectly applicable.
HPS Recommendations on Radiation Dose Limits for the General Public
HPS endorses the dose limits for human-made sources recommended
by NCRP (1993a) and adopted by the Nuclear Regulatory Commission (1991),
noting that they are sufficiently conservative for public-health protection,
compliance can be verified by actual measurement, they can be achieved in
most cases without sacrificing important public benefits, and they can be applied
without discrimination to essentially all human-made sources.
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OTHER GUIDANCES FOR TENORM
187
HPS Recommendations on Radiation Standards for Site Cleanup and
Restoration
below.
Regarding radiation standards for site cleanup and restoration, HPS
recommends that radiation-protection standards be based on health risks and be
clearly related to quantities that can be measured, such as radiation exposure
rates or radionuclide concentrations in soil, on equipment, or in buildings.
Standards should be consistent with the fundamental principles recommended
for all radiation-protection activities, including for example, that radiation doses
be ALARA.
The seven specific recommendations made by HPS are summarized
· Remedial action should do more good than harm.
· For decisions on decommissioning strategies, the ALARA
principle should be applied to the total radiation dose to society,
including workers at the site as well as the general public.
· For unrestricted use of a restored site, HPS endorses the limit
of 1 mSv for the total effective dose equivalents (TEDE) to any
member of the public in any one year from all nonmedical, human-
made sources combined recommended by ICRP (1991) and NCRP
(1993a). For site cleanup and restoration standards, HPS
recommends that the dose limit be applied to all site-specific,
nonoccupational sources, except indoor radon, including natural
radionuclides whose concentrations have been enhanced by human
activities.
· HPS recommends that a compliance screening level of 0.25
mSv (25 mrem) be applied to the mean annual TEDE to the
"critical population group," defined as the most highly exposed
homogeneous group affected by the restored site. If the mean
6Total effective dose equivalent is used by some organizations to emphasize that
the sum of the contributions from external and internal sources is meant. This
term is not a part of the recommendations of ICRP or NCRP. Effective dose
equivalent, without the modifier total, is sufficient to imply contributions from
external and internal sources.
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188
GUIDELINES FOR EXPOSURE TO TENORM
annual TEDE to the critical group is likely to exceed 25 mrem, an
evaluation should be made to ensure that no individual is likely to
receive an annual TEDE exceeding 1 mSv (100 mrem) from all
site-specific, nonoccupational sources, excluding indoor radon.
· HPS recommends that standards for site cleanup and
restoration include an assessment screening level, below which
further dose assessment is not required. For all site-specific,
nonoccupational sources of radiation exposure, excluding indoor
radon, HPS recommends an assessment screening level of 0.05
mSv (5 mrem) for an annual mean TEDE to the critical group.
· For unrestricted release of sites containing radium-226,
radium-228, or thorium-232, HPS recommends a soil
concentration limit of 0.2 Bq/g (5 pCi/g) above the normal
concentration for the region to prevent excessive radon-222 or
radon-220 concentrations in indoor air. It further recommends that
the concentration be averaged over an area of 25-100 m2 and a soil
depth of 1 m. A screening level for the same nuclides of 0.04 Bq/g
(1 pCi/g) above the normal concentration for the region, averaged
over the same area and depth, is also recommended.
· HPS recommends that standards for site cleanup and
restoration be based on probabilistic risk assessments designed to
provide the best estimates of the distributions and uncertainties of
doses that are likely to be received after restoration through the use
of state-of-the-art, peer-reviewed, thoroughly documented
mathematical models and computer codes.
NUCLEAR REGULATORY COMMISSION
The Nuclear Regulatory Commission is not authorized to regulate
TENORM as defined in this study, because such materials exclude source,
special nuclear, and byproduct materials as defined in the Atomic Energy Act
and the Nuclear Regulatory Commission's licensing authority is derived entirely
from the act (see chapter 6~. However, the Nuclear Regulatory Commission has
issued regulations and guidance for licensed radioactive materials that are
potentially relevant to regulation of TENORM.
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OTHER GUIDANCES FOR TENORM
Regulations for Decommissioning of Licensed Facilities
189
In 1997, the Nuclear Regulatory Commission established radiologic
criteria in 10 CFR Part 20 for decontamination and decommissioning of licensed
nuclear facilities (62 FR 39058~. The standards apply to all licensed facilities
except uranium- and thorium-recovery facilities subject to 10 CFR Part 40,
Appendix A (for example, mill tailing sites) and uranium-solution extraction
facilities. The standards define conditions under which sites may be released for
unrestricted use by the public or released under restricted conditions.
The standards specify that sites will be considered acceptable for
unrestricted use if the annual effective dose equivalent to average individuals in
the critical group does not exceed 0.25 mSv (25 mrem), including the dose from
groundwater sources of drinking water, and the residual radioactivity has been
reduced to levels that are ALARA. If the dose constraint of 0.25 mSv per year
for unrestricted use is not reasonably achievable or if compliance with the dose
constraint would result in net harm, sites will be considered acceptable for
license termination under restricted conditions if provisions for legally
enforceable institutional controls would provide reasonable assurance that the
annual effective dose equivalent will not exceed 0.25 mSv (25 mrem) or the
annual effective dose equivalent is ALARA and would not exceed 1 mSv (100
mrem) for unrestricted use if the institutional controls were no longer in effect
or 5 mSv (500 mrem) if compliance with the 1-mSv criterion is not achievable,
is prohibitively expensive, or would result in net harm. The kinds of institutional
controls over contaminated sites that would be effective in limiting exposures of
the public include government custodianship and land-use restrictions specified
in deeds. The regulations also specify that a licensee must provide sufficient
financial assurance to allow appropriate institutional controls to be maintained.
The standards described above apply to human-made radionuclides and
to the levels of naturally occurring radionuclides above background, and the
standards apply for 1,000 y after decommissioning.
Guidance on Disposal of Residual Thorium or Uranium
Earlier Nuclear Regulatory Commission guidance relevant to
TENORM addresses disposal of residual thorium or uranium from past
processing operations (Nuclear Regulatory Commission 1981~. The guidance
discusses several options for disposal of the residual radioactive materials that
depend on the concentrations of uranium and thorium; materials containing
higher concentrations require more-restrictive disposal methods and controls on
land use at the disposal site. The particular option that has been used most often
and is particularly relevant to regulation of TENORM is described below.
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190
GUIDELINES FOR EXPOSURE TO TENORM
The Nuclear Regulatory Commission guidance specifies that residual
thorium or uranium may be disposed of with no restrictions on burial method if
the concentrations do not exceed:
· 0.4 Bq/g (10 pCi/g) for natural thorium or uranium with their
decay products present and in equilibrium.
· 1.3 Bq/g (35 pCi/g) for depleted uranium.
· 1.1 Bq/g (30 pCi/g) for enriched uranium.
The Nuclear Regulatory Commission also intended that these
concentration limits would define acceptable remediation of contaminated sites
to permit unrestricted use by the public. The limits may still be used for
remediation even though, as described in the previous section, the Nuclear
Regulatory Commission has since issued more-general dose-based standards for
unrestricted release of contaminated sites (Nuclear Regulatory Commission
1997a).
The concentration limits given above were based on two considerations
(Nuclear Regulatory Commission 1981~. First, the limit of 0.4 Bq/g (10 pCi/g)
for natural uranium or thorium is simply an average of EPA's cleanup standards
for radium in contaminated soil of 0.2 Bq/g (5 pCi/g) in the top 15 cm and 0.6
Bq/g (15 pCi/g) below 15 cm, as specified in Subpart B of the mill-tailings
standards in 40 CFR Part 192 (see chapter 7~. The cleanup standards for radium
in contaminated soil at mill-tailings sites are relevant for natural uranium or
thorium with their decay products present and in equilibrium because radium
and its decay products are the most important radionuclides in these materials.
Second, the concentration limits for depleted and enriched uranium
were intended to correspond to a limit on annual absorbed dose of alpha
particles of 0.01 mGy (1 mrad) to the lungs or 0.03 mGy (3 mrad) to bone,7
which EPA had used in developing proposed guidance on transuranium
elements in the environment (EPA 19774. The concentration limits were derived
from the assumed dose constraints on the basis of an analysis of inhalation and
ingestion pathways for an assumed exposure scenario (Nuclear Regulatory
Commission 1981~.
As discussed later in this chapter, an exemption level or cleanup
standard for 226Ra of 1.1 Bq/g (30 pCi/g) is contained in some state regulations
7For purposes of radiation protection, the dose equivalent from irradiation by
alpha particles often is assumed to be 20 times higher than the absorbed dose
(NCRP 1993a; ICRP 19919.
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OTHER GUIDANCES FOR TENORM
191
for TENORM. This value also has been applied to unrestricted disposal of waste
materials that contain uranium in sanitary landfills at DOE sites (for example,
Lee and others 1 996; 1 995; Kocher and O'Donnell 1 987~.
DEPARTMENT OF ENERGY
The Department of Energy (DOE) is responsible for regulating
TENORM arising from any of its authorized activities (see chapter 6~. DOE
manages and disposes of wastes that contain TENORM in two ways, depending
primarily on the volume of the waste material.
Management and Disposal of Small Volumes of TENORM
Current DOE requirements for management and disposal of radioactive
waste (DOE 1988) specify that small volumes of waste containing TENORM
may be managed as low-level waste. The waste volumes that may be so
managed are not specified, but the volumes must be sufficiently small that the
waste-acceptance criteria for the intended low-level waste disposal facility
would be met. Thus, this option normally would be used for discrete sources.
In addition to the requirement for compliance with a limit on annual
effective dose equivalent of 1 mSv (100 mrem) for individual members of the
public from all DOE sources combined (DOE 1990), acceptable disposals of
low-level waste at DOE sites are defined by the following performance
objectives for the disposal facility (DOE 1988~:
· A limit on annual effective dose equivalent for individual
members of the public of 0.25 mSv (25 mrem) from all release and
exposure pathways combined.
· Limits on releases of radionuclides to the atmosphere such that
the requirements of EPA's 40 CFR Part 61 (see chapter 7) are met.
· Reasonable efforts to maintain releases of radioactivity to the
general environment ALARA.
· A limit on effective dose equivalent for individuals who might
inadvertently intrude onto the disposal site after loss of active
institutional controls (assumed to occur 100y after disposal) of
1 mSv per year (100 mrem per year) for continuous exposure or
5 mSv (500 mrem) for a single acute exposure.
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192
GUIDELINES FOR EXPOSURE TO TENORM
· Protection of groundwater resources consistent with federal,
state, and local requirements.
The performance objective for individual members of the public is
consistent with a similar performance objective for commercial low-level waste
disposal facilities that had been established by the Nuclear Regulatory
Commission (1982a). The dose criteria in the performance objective for
inadvertent intruders are the same as the dose limits from all DOE sources
combined (DOE 1990) and are consistent with EPA's proposed federal guidance
on radiation protection of the public (EPA 1994d) discussed in chapter7.
Finally, the performance objective for protection of groundwater resources often
has been interpreted in terms of compliance with EPA's interim or proposed
standards for radioactivity in drinking water (40 CFR Part 141) discussed in
chapter 7.
Management and Disposal of Larger Volumes of TENOR1`I
At DOE sites, larger volumes of waste containing TENORM (diffuse
sources) that cannot be managed as low-level waste may be managed as
uranium or thorium mill tailings (DOE 1988~. Thus, these materials are intended
for disposal at specially designated DOE sites or at mill tailings disposal sites
established under the Uranium Mill Tailings Radiation Control Act.
The requirements for control of residual radioactive materials at DOE
sites that apply to TENORM managed as mill tailings are contained in
Order 5400.5 (DOE 1990~. The requirements address release of contaminated
property for unrestricted use by the public, interim storage of residual
radioactive material, and long-term management of uranium, thorium, and their
decay products.
In all situations involving management and disposal of residual
radioactive material, the requirements for radiation protection of the public
(DOE 1990) must be met. These include a limit on annual effective dose
equivalent of 1 mSv (100 mrem) for individual members of the public from all
routine DOE activities and exposure to the residual radioactive material. Higher
doses from acute exposure are permitted if the annual effective dose equivalent
averaged over a lifetime is not expected to exceed 1 mSv (lOOmrem). In
addition, residual radioactivity shall be reduced in accordance with the ALARA
objective. As noted in the previous section, radiation protection requirements at
DOE sites are consistent with EPA's proposed federal guidance on radiation
protection of the public (EPA 1 994d).
The requirements for release of contaminated property (land and
structures) for unrestricted use by the public are the same as the guidelines for
residual radioactivity developed in the Formerly Utilized Sites Remedial Action
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OTHER GUIDANCES FOR TENORM
193
Program (FUSRAP) and the Surplus Facilities Management Program (SFMP)
(DOE 1997~. Those guidelines include the following provisions, subject to the
overriding requirement of compliance with the annual dose limit of 1 mSv
(100 mrem) from all DOE sources combined:
· Limits on residual concentrations of radium and thorium in soil,
airborne radon decay products in occupied or habitable structures on
private property, and external gamma radiation level inside buildings
or habitable structures on a site as given in Subpart B of EPA's mill
tailings standards in 40 CFR Part 192.
· Limits on residual concentrations of other radionuclides in soil
shall be derived from the annual dose limit of 1 mSv (100 mrem) in
radiation-protection requirements using prescribed site-specific
procedures and data.
· Limits on residual radioactivity on surfaces of structures and
equipment on the basis of guidelines developed by the Nuclear
Regulatory Commission (1982b; 1974~.
· Limits on residual concentrations of radionuclides in air and
water such that appropriate federal and state standards will be met.
The requirements for interim storage of residual radioactive materials
also are obtained from the guidelines for FUSRAP and remote SFMP sites and
include the following provisions:
· Limits on 222Rn concentrations in air above background of
3.7 kBq/m3 (100 pCi/L) at any point within a she, 1.1 kBq/m3
(30 pCi/L) averaged over a year and over a site, and 0.11 kBq/m3
(3 pCi/L) averaged over a year at any location outside a site.
· A limit on release rate of 222Rn above background of 0.7 Bq/m2
(20 pCi/m2) per second on the basis of a similar provision in
Subparts A and D of EPA's mill tailings standards in 40 CFR
Part 192.
· Limits on radionuclide concentrations in groundwater or
quantities of residual radioactive material as established in federal or
state standards.
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GUIDELINES FOR EXPOSURE TO TENORM
· Control and stabilization features designed to ensure, to the
extent reasonably achievable, an effective life of 50 y, with a
minimum life of 25 years.
Finally, the requirements for long-term management of uranium,
thorium, and their decay products, which also are obtained from the guidelines
for FUSRAP and remote SFMP sites, include the following provisions:
· Limits on the release rate of 222Rn to the atmosphere and the
concentration in air outside the boundary of the contaminated area as
given in Subpart A of EPA's mill tailings standards in 40 CFR
Part 192.
· Protection of groundwater in accordance with applicable DOE
orders and federal and state standards.
· A design lifetime for control and stabilization features as given
in Subpart A of EPA's mill tailings standards in 40 CFR Part 192 .
· Control of access to the site and prevention of misuse of on-site
residual radioactive material by appropriate administrative controls
and physical barriers designed to be effective, to the extent
reasonable, for at least 200 y.
In summary, DOE requirements for management and disposal of larger
volumes of waste containing TENORM that cannot be managed as low-level
waste are based primarily on two considerations:
· Compliance with the annual dose limit of 1 mSv (100 mrem) for
individual members of the public from all routine DOE activities
combined, including exposure to TENORM and other residual
radioactive material, as specified in Order 5400.5 (DOE 1990~.
· Compliance with provisions for residual radioactive material
based primarily on EPA's standards for uranium and thorium mill
tailings in 40 CFR Part 192.
In addition, airborne releases from DOE sites, including releases of TENORM,
must comply with the provisions of EPA's 40 CFR Part 61.
DOE's requirements for radiation protection of the public and the
environment are being revised (DOE 1993a). The requirements for management
of property contaminated with residual radioactive material, including
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OTHER GUIDANCES FOR TENORM
195
TENORM, might be modified somewhat from the current requirements in Order
5400.5 (DOE 1990) discussed here.
STATE STANDARDS AND GUIDELINES
The Conference of Radiation Control Program Directors (CRCPD) was
established in 1968 to serve as a common forum for state radiation-control
programs in the United States to communicate with each other and with the
many federal agencies that have radiation-protection responsibilities. The major
technical work of CRCPD is accomplished through various working groups. In
addition to about 50 smaller working groups, CRCPD has a special commission
to develop suggested state regulations for the regulation and control of
TENORM (CRCPD 1998~. CRCPD has a long history of involvement in the
TENORM issue. Its 1978 task-force report on natural-radioactivity
contamination problems (CRCPD 1978), prepared in cooperation with EPA's
Office of Radiation Programs, was one of the first assessments of the scope of
the problem and of potential radiation-control measures.
Since 1990, CRCPD has published Suggested State Regulations for the
Control of Radiation (SSRCR). SSRCR generally parallels federal radiation-
protection regulations but contains additional provisions on subjects regulated at
the state, but not federal, level. Such additional subjects include nonionizing
radiation and x-ray use in medicine. CRCPD has drafted TENORM regulations
as Part N of SSRCR (Reynolds 1995~.
The February 1997 draft of Part N (CRCPD 1997) provides for the
licensing of TENORM-generating industries and includes the following selected
provisions (relevant sections of Part N are shown in parentheses):
· Operations, uses, or transfers of TENORM are to be conducted
in a manner such that no member of the public will receive an annual
total effective dose equivalent (excluding radon and its decay
products) of 1 mSv (100 mrem) from all licensed sources, including
TENORM sources (N.5.a). Part N does not specify what fraction of
the 1-mSv (100-mrem) dose limit can come from the TENORM
disposed of or released for unrestricted use; that determination is to
be made by the implementing state in light of existing federal
standards to protect the general public (N.5.e). However, generally
applicable decontamination and decommissioning standards being
developed by a CRCPD working group for Part D of SSRCR call for
air and water releases and soil-contamination levels to meet a 0.15-
mSv (15-mrem) annual dose constraint, in line with current EPA
guidance (Luftig and Weinstock 1997~.
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GUIDELINES FOR EXPOSURE TO TENORM
· Use, transfer, or disposal of TENORM is to be conducted to
prevent accumulation of radon in residential structures, schools, and
other public buildings in concentrations exceeding 150 Bq/m3 (4
pCi/L). Compliance with this standard may be demonstrated by
imposition of institutional controls or adherence to building codes.
Institutional controls may include deed restriction or notification,
recorded in the property title or by the placement of permanent
markers, that TENORM has been disposed of at Me site (N.5.d).
· For radium-bearing TENORM, materials containing 226Ra or
228Ra at less than 0.2 Bq/g (5 pCi/g) are exempt from licensing
(N.4.a.i).
· Purposeful dilution to render TENORM exempt is not allowed
(N.4.a.iii).
· Land may not be released for unrestricted use where the soil
concentration of 226Ra or 228Ra (averaged over any 100 m2 and to a
depth of 15 cm) exceeds 0.2 Bq/g (5 pCi/g). This limit and the
exemption limit for licensing may be relaxed if dose assessment
shows that the indoor-radon and other criteria in Section N.5 are met
(N.7.b).
· The disposal methods used with uranium mill tailings regulated
under 40 CFR 192 are generally acceptable for TENORM. However,
other disposal methods meeting the basic criteria in Section N.S
might also be suitable, such as downhole disposal of some oilfield
wastes, landfill disposal, and on-site disposal in conjunction with
institutional controls. Cost-benefit analysis may be used to evaluate
such alternative disposal options (N.8.a).
A wide variety of regulatory control is exercised over TENORM by states.
Some states rely on general regulations for the control of radiation. Others have
enacted or are considering regulations addressing TENORM site cleanup
(specifically, radium concentration in soil; see table 9.1), contamination of
equipment, and disposal options. The current state-by-state regulatory picture is
given by Peter Gray & Associates (1997~.
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OTHER GUIDANCES FOR TENORM
Table 9.1. State regulations on TENORM; soil 226Ra site cleanup standards
(adapted from Peter Gray & Associates, 1997).
State
226Ra cleanup standard
Bq/kg (pCi/g)
Arkansas
Colorado (proposed)
Georgia
Louisiana
Michigan (proposed)
Mississippi
New Mexico
North Dakota
New Jersey
Oklahoma (proposed)
Oregon
South Carolina
Texas
Conference of Radiation Control
Program Directors
200/15 (5/15)a
200/15
200/15 with high radon factors
1,100/15 (30/15)C with low radon factor
200/15 or 1,100 if the effective dose equivalent to
members of the public does not exceed 1 mSv
(100 mrem) per year
200/15
200/15 with high radon factor
1,100 with low radon factor
1,100/15
200
Variable-depending on concentrations and
volumes. Annual dose less than 0.15 mSv (15
mrem)
1,100/15
200/15
200/15 with high radon factor
1,100/15 with low radon factor
200/15 with high radon factor
1,100/15 with low radon factor
200/15
197
a-200/15" is 200 Bq/kg (5 pCi/g) of radium in soil, averaged over any 100 square meters and
averaged over the 15 centimeters of soil below the surface.
bHigh radon factor is a radon emanation rate greater than 0.7 Bq (20 psi) per square meter per
second. This radon flux rate is the post-remedial action level specified for the disposal of uranium
mill tailings in 40 CFR 192.02. Low radon factor is a radon emanation rate less than 0.7 Bq (20
psi) per square meter per second.
C-1,100/15" is 1,100 Bq/kg (30 pCi/g) of radium in soil, averaged over any 100 square meters and
averaged over the first 15 centimeters of soil below the surface.
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198
GUIDELINES FOR EXPOSURE TO TENORM
INTERNATIONAL ATOMIC ENERGY AGENCY
The current International Atomic Energy Agency (IAEA) guidance on
radiation protection of the public is contained in the basic safety standards
(L\EA 1996a) discussed in chapter 6. Those standards include two provisions
that are applicable to TENORM other than indoor radon.
First, paragraph 2.5 of the "Requirements for Practices" specifies that
"exposure to natural sources shall normally be considered as a chronic exposure
situation and, if necessary, shall be subject to the requirements for intervention,
except that ... public exposure delivered by effluent discharges or the disposal
of radioactive waste arising from a practice involving natural sources shall be
subject to the requirements for practices ..., unless the exposure is excluded or
the practice or the source is exempted." In that statement, practice and
intervention have the same meanings as in ICRP recommendations discussed
-
earlier in this chapter, requirements for practices include a limit on annual
effective dose of 1 mSv (100 mrem) from all sources combined, and excluded
exposures include exposures to most raw materials that contain unmodified
concentrations of naturally occurring radionuclides. Thus, the standards
encourage the regulation of some exposures to TENORM as practices and their
being subjected to the annual dose limit of 1 mSv (100 mrem) from all sources
combined. That approach differs from ICRP recommendations for interventions
involving TENORM other than indoor radon discussed earlier, which do not
include a dose limit. However, because ICRP had not developed a
recommended dose limit for protection against exposure to natural sources, the
IAEA's standards also include the statement that "the General Obligations for
practices concerning protection against natural sources will be that exposure to
natural sources, which is normally a chronic exposure situation, should be
subject to intervention and ... the requirements for practices should be generally
limited to radon, the exposure to other natural sources being expected to be dealt
with by exclusion or exemption of the source or otherwise at the discretion of
the Regulatory Authority." Thus, IAEA intends that exposures of the public to
TENORM other than indoor radon be controlled in accordance with ICRP
recommendations for interventions and that the dose limit for practices not be
applied.
Second, LAEA's standards include recommendations for the exemption
from regulatory control of TENORM containing low activity concentrations and
low total activities, as indicated in the statements on the "Requirements for
Practices" given above. The exemption levels for naturally occurring
radionuclides were developed on the basis of the following considerations:
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OTHER GUIDANCES FOR TENORM
· The annual effective dose for individual members of the public
from the exempted practice or source should not exceed about
10 pSv (1 mrem).
· The annual collective effective dose from the exempted practice
or source should not exceed about 1 person-Sv (100 person-rem).
· A series of bounding exposure scenarios for use and disposal are
assumed.
· The application of exemption to natural sources, where these are
not excluded, is limited to the incorporation of naturally occurring
radionuclides into consumer products or their use as a radioactive
source or for their elemental properties.
199
The first two considerations are taken from previous LAEA
recommendations on exemption principles (IAEA 1988~. The last consideration
indicates that the exemption levels for naturally occurring radionuclides apply
only to intentional and beneficial uses of these radionuclides and therefore do
not apply to residual radioactive materials or other wastes containing TENORM.
For the most important naturally occurring radionuclides other than
radon, the recommended exemption levels are as follows:
· For natural uranium or thorium, an activity concentration of
1 Bq/g (27 pCi/g) and a total activity of 103 Bq (27 nCi).
· For 226Ra, an activity concentration of 10 Bq/g (270 pCi/g) and a
total activity of 104 Bq (270 nCi).
· For 228Ra, an activity concentration of 10 Bq/g (270 pCi/g) and a
total activity of 105 Bq (2.7 psi).
· For Pub, an activity concentration of 10 Bq/g (270 pCi/g) and a
total activity of 104 Bq (270 nCi).
In each case, all decay products are assumed to be present and in equilibrium.
Especially for uranium, thorium, and radium, the recommended
exemption levels given above are substantially higher than EPA's standards for
cleanup of residual radioactive material at mill tailings sites, as given in
Subpart B of 40 CFR Part 192 (see chapter 7~. However, as noted previously,
the recommended exemption levels for naturally occurring radionuclides do not
apply to residual radioactive materials that contain TENORM.
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200
GUIDELINES FOR EXPOSURE TO TENORM
COMMISSION OF THE EUROPEAN COMMUNITIES AND OTHER
NATIONS
The Commission of the European Communities (CEC) has issued
revised directives for radiation-protection standards that should be implemented
by member states of the European Union by the year2000 (see chapter 6~.
Title VII of the standards addresses substantial increases in exposure due to
natural radiation sources. In particular, the standards call attention, first, to
operations with and storage of materials not usually regarded as radioactive but
that contain naturally occurring radionuclides and cause a substantial increase in
exposures of the public, and second, to activities that lead to the production of
residues not usually regarded as radioactive but that contain naturally occurring
radionuclides and cause a substantial increase in exposures of the public.
However, the CEC standards do not include any additional guidance on suitable
approaches to regulating the identified exposure situations involving TENORM
(such as guidance on a dose limit).
The committee has not endeavored to obtain information on standards
for TENORM, especially in the form of a dose limit, that have been established
in other countries. However, in discussions of ICRP recommendations for
natural sources, Clarke (1996; 1995) noted that many countries have established
an annual dose constraint for specific practices or sources of about 0.3 mSv
(30 mrem) and that this dose constraint logically could be applied to unrestricted
release of contaminated sites that were licensed for such activities as uranium
mining or milling and then decommissioned. In response to this suggestion, the
committee notes that an annual dose constraint of 0.3 mSv (30 mrem)
corresponds to a concentration of 226Ra in surface soil that is only about half the
cleanup criterion for radium specified in Subpart B of EPA's standards for mill
tailings in 40 CFR Part 192.
The European Union directives (Euratom 1996) differ from the IDEA
basic safety standards (LAEA 1996a) by including in Title VII, a special
provision that takes care of substantial increases in exposure due to natural
radiation sources. Member states of CEC might reach different derived limits for
226Rn that take into account peculiarities of industrial processes and specificity
of industrial sites and waste repositories. By the year 2000, CEC member states
will have to comply with the European Union directives (Euratom 1996~.
TRANSFERABILITY OF STANDARDS
A 226Ra concentration in soil of 0.2 Bq/g (5 pCi/g) appears frequently
in federal and state regulations dealing with TENORM disposal or she cleanup.
It derives from standard-setting during the early 1980s (40 CFR 192) associated
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OTHER GUIDANCES FOR TENORM
201
with the Uranium Mill Tailings Radiation Control Act of 1978 (UMTRCA).
UMTRCA governs remedial actions for uranium mill tailings disposal sites and
discontinued uranium-milling facilities. It covers the disposal of the impounded
tailings and other wastes associated with the extraction of uranium and thorium,
and the dispersed tailings and associated wastes that have contaminated
surrounding land, buildings, and soil (see chapter 7~. The impounded tailings,
classified as byproduct materials under the Atomic Energy Act, are typically of
much higher activity concentration tabout 300-1,000 pCi/g (11-37 Bq/g)] than
the contaminated soils in the latter group and are intended to be maintained in
perpetuity under federal or state control. The diffuse TENORM considered in
this report typically has an activity concentration similar to that seen in the soils
contaminated by dispersed tailings. The I3MTRCA regulation addressing these
soils (hereafter referred to as the soil-radium cleanup standard) calls for the
concentration of 226Ra in remediated sites not to exceed background levels by
more than 0.2 Bq/g (5 pCi/g) in the uppermost 15 cm of soil or more than 0.6
Bq/g (15 pCi/g) in subsurface layers.
Alternative cleanup standards for contaminated sites covered by 40
CFR 192 Mat were considered, but not adopted, by EPA during the drafting of
the regulations would have allowed an average 226Ra concentration of 0.2, 0.6,
or 1.1 Bq/g (5, 15, or 30 pCi/g) at all depths in the soil; 1.1 Bq/g (30 pCi/g) is
the present cleanup standard in some state regulations. Under a conservative
external-exposure model (one that assumes continuous exposure to an infinite
quantity of material), a 226Ra concentration in soil of 1.1 Bq/g (30 pCi/g) results
in an estimated annual dose of 4.7 mSv (470 mrem) to the maximally exposed
individual-close to the federal radiation-protection guidance for exposure of
the general public from all sources combined that was then set at 5 mSv (500
mrem) (EPA 1982~.
The Nuclear Regulatory Commission has applied the soil-radium
cleanup standard to the decommissioning of active, Nuclear Regulatory
Commission-licensed uranium mills (10 CFR 40; Appendix A). Additional
examples of the regulatory extension of the soil-radium cleanup standard to
waste materials other than uranium mill tailings can be seen in other remedial
programs managed by DOE and EPA. DOE guidelines for soil cleanup at
FUSRAP sites use this soil-radium standard (DOE 1997~. EPA is using the
standard from 40 CFR 192 as an applicable or relevant and appropriate
requirement in establishing cleanup levels for CERCLA (Comprehensive
Environmental Response, Compensation, and Liability Act) sites with 226Ra
contamination, as opposed to the annual dose constraint of 0.15 mSv (15 mrem)
in current cleanup guidance (Luitig and Weinstock 1997~. Finally, and of
considerable practical importance to regulation of TENORM, the standard and
variations on it discussed below form the basis of many existing and proposed
state regulations dealing with TENORM.
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202
GUIDELINES FOR EXPOSURE TO TENORM
The soil-radium cleanup standard has been extended broadly to
encompass soil contamination by other uranium- and thorium-series
radionuclides. For example, the dose associated with the soil-radium cleanup
standard is being considered by the Nuclear Regulatory Commission as a
benchmark for the cleanup of other radionuclides in connection with license
termination at uranium and thorium mills and in situ leach (specifically,
uranium solution extraction) facilities (Nuclear Regulatory Commission 1997c).
A 1993 memo from the director of EPA's Office of Radiation and Indoor Air
regarding the application of the 40 CFR 192 soil-radium cleanup standard to
soils at a New Jersey FUSRAP site (and other non-UMTRCA sites) notes that
the concentration criterion for surface soil was developed for the UMTRCA
sites and that one would have to determine whether the risk scenarios at this
FUSRAP site were sufficiently similar to those at UMTRCA sites to warrant the
use of this health-based standard (EPA 1993a). This concern also applies to the
non-fuel-cycle TENORM considered in this study.
The scientific validity of applying the soil-radium cleanup standard to
TENORM wastes outside the nuclear fuel cycle, including industrial materials
that are not classified as wastes, depends on the degree of similarity that such
materials exhibit to the UMTRCA materials for which the standard was derived.
Yet many non-fuel-cycle TENORM have initial mineralogies and processing
histories different from uranium mill tailings. This results in materials in which
the radionuclides can have different radon-emanation coefficients, solubilities,
and bioavailabilities from uranium mill tailings. The zircon-bearing sands used
in the metal-casting industry are a case in point. The occurrence of zircons as
detrital minerals in river and beach sands is due to this mineral's high resistance
to mechanical and chemical weathering. Leaching of radionuclides from zircons
is low (Faure 1986~. In contrast, radium and other radionuclides in uranium mill
tailings are quite leachable (Landa 1982; 1980~. Whereas uranium-mill tailings
tend to have radon-emanation coefficients of about 10-40%, the values for
zircons tend to be less than 5%. Thus, because of substantially lower leaching
and radon emanation exhibited by zircon sands, the environmental mobility of
radionuclides from these materials is much lower than that of radionuclides
from uranium mill tailings. As a result, the potential for internal radiation
exposure from a zircon source (such as leaching of radionuclides into
groundwater and emanation of radon to the atmosphere) is considerably lower
than the potential for internal exposure from UMTRCA materials.
However, whereas the low-release properties of some TENORM might
limit the radon decay-product dose and internal dose contributions from other
radionuclides, the external exposure must also be considered (table 2.8~. If we
consider a hypothetical, unshielded individual spending 100% of his or her time
residing on homogeneous soil of infinite thickness, a 226Ra concentration of 0.2
Bq/g (5 pCi/g), whether in the form of uranium mill tailings or any other
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OTHER GUIDANCES FOR TENON
203
rad~um-containing TENORM, will contribute more than half the 1-mSv (100-
mrem) annual dose limit for public exposures permitted under the proposed
federal radiation guidance (EPA 1994d). Incremental increases in radium
concentrations in the soil of 0.24-0.4 Bq/g (6-10 pCi/g) would contribute a
larger proportion of the 1-mSv (100-mrem) annual dose limit and would exceed
the limit at the upper end. Shielding by an uncontaminated earthen cover and a
decreased time of exposure would reduce the external dose from radium in the
soil.
Finally, considering the 0.15-mSv (15-mrem) annual dose constraint
deemed protective by EPA (Luftig and Weinstock 1997) and focusing only on
external exposure, we note that this dose is equivalent to an incremental increase
in the 226Ra concentration in soil of about 0.04 Bq/g (1 pCi/g), that is, an amount
about equal to the average background concentration. In view of the spatial
variability (both areal and within the soil profiled in natural background levels
and in view of sampling and analytic uncertainties, it will likely be difficult to
implement a 0.15-mSv (15-mrem) soil-cleanup standard for radium, particularly
when the contamination is only marginally above the local background.
Representative terms from entire chapter:
mill tailings
