ML20133H268
| ML20133H268 | |
| Person / Time | |
|---|---|
| Issue date: | 11/25/1996 |
| From: | Hoyle J NRC OFFICE OF THE SECRETARY (SECY) |
| To: | |
| References | |
| FRN-60FR15180, RULE-PR-60 NUDOCS 9701170114 | |
| Download: ML20133H268 (97) | |
Text
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i NUCLEAR REGULATORY COMMISSIO%FFICE OF SECRE TARY 00CKETING & SERVICE l
10 CFR Part 60 BRANCH I
RIN:
3150-AD51 q
Disposal of High-Level Radioactive Wastes in Geologic Repositories; Design Basis. Events 1
l i
j AGENCY: Nuclear Regulatory Commission.
3 ACTION: Final rule.
SUMMARY
The Nuclear Regulatory Commission is amending its 7
regulations on the protection of public health and safety from f
activities conducted at a geologic repository operations area l
(GROA) before permAn*2nt closurr.
In phrtici'lar, thG final rule i
addresses the measures that are required to provide defense in depth against the consequences of " design basis events."
These i
measures include prescribed design requirements, quality assurance requirements, and the establishment of a preclosure l
controlled area from which members of the public can be excluded.
l-l EFFECTIVE DATE:
1996 [30 days from date of O
publication in the Federal Register].
/
j.
FOR FURTHER INFORMATION, CONTACT:
Dr. Richard A. Weller, I
Division of Waste Management, Office of Nuclear Material Safety i
i 9701170114 961125 PDR PR 60 60FR15100 PDR i
h,u
. Dn 12 fL l
Dsu da m
and Safeguards, U.S. Nuclear Regulatory Commission, Washington, DC 20555, telephone (301) 415-7287.
SUPPLEMENTARY INFORMATION:
9 Background
Under the Nuclear Waste Policy Act of 1982, as amended, the U.S. Nuclear Regulatory Commission exercises licensing.and related regulatory authority with respect to geologic repositories that are to be constructed and operated by the U.S. Department of Energy (DOE) for the disposal of high-level radioactive waste.
The Commission's regulations pertaining to In recent these geologic repositories appear at 10 CFR Part 60.
years, NRC, in conjunction with its Federally-Funded Research and Development Center, the Center for Nuclear Waste Regulatory Analyses, completed a ccmprehensive review of the requirements of Part 60 regarding their clarity and sufficiency to protect.public health and safety.
NRC focused particular attention on any f
matters that may be ambiguous, insufficient for their intended i
)
or inconsistent with other expressions of its regulatory
- purpose, policy.
Independently, DOE conducted a similar review of Part 60.
The NRC review identified deficiencies regarding the clarity and sufficiency of the current Part 60 requirements to protect 2
1 see the and the partial grant / partial denial of the DOE petition, Federal Register notices cited above.
As noted in the Federal Register notice for the proposed rule (60 FR 15180) and as intended in subsequent discussions in this notice, unless the specific context suggests otherwise, the terms " provisions,"
" requirements," " standards," and " criteria" are generally used interchangeably; the term " limit" (as in " dose limit") is generally used to refer to a specific type of requirement or
]
criterion; and the term " rule" is generally used to refer to the ertire set of requirements or criteria (e.g.,
Part 60).
This i
final rule completes NRC action related to PRM-60-3.
Lastly, the Commission notes that, consistent with the mandates of the Energy Policy Act of 1992, the Environmental Protection Agency (EPA) is developing site-specific environmental j
radiation protection standards for a potential repository at Yucca Mountain, Nevada.
In this regard, the Act specifies that, within one year after promulgation of the EPA standards, the Commission must promulgate a rule so that Commission regulations are consistent with the new EPA standards.
Although the primary focus of the new EPA standards is on the postclosure period of repository performance, the staff will ensure that the current modifications to Part 60 proposed herein, which focus on the period of repository operations before permanent closure, are consistent with the new EPA standards.
To the extent any inconsistencies between NRC and EPA requirements are identified, 4
I l
public health and safety for the full range of credible l
conditions or events that may occur at an operating repository, including those. low-probability events that have potentially serious consequences.
NRC also noted that certain elements of existing Part 60 differ from counterpart requirements in other NRC rules where greater consistency in language would be i
beneficial.
DOE's independent review of Part 60 requirements identified similar deficiencies in these requirements.
To j
address these issues, DOE filed a petition-for rulemaking (PRM),
i j
PRM-60-3, on April 19, 1990.
5
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l In response to the DOE petition Snd the results of the NRC review of Part 60, the Commission published a proposed rule for i
j public comment in the Federal Register on March 22, 1995
}
(60 FR 15180) to clarify the requirements for protection of
?
public health and safety related to activities conducted at a
j i
GROA be* ore its permanent closure.
In particular, the proposed i
rule provided new and modified definitions for certain terms 1
l (including the definition of "important to safety," with 4
reference to structures, systems, and components), dose cr..teria i
{
for accident conditions, and requirements for the establishment i
l of a preclosure controlled area from which members of the public j
ca'n be excluded when necessary.
In an accompanying notice (March 22, 1995; 60 FR 15190) the Commission also granted in
,i part, and denied in part, the specific proposals in the DOE petition.
For a fuller discussion of the PRM, the proposed rule, 3
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I i
4 they will be addressed in the planned future rulemaking by NRC to 1
address new EPA standards.
i Public Comments on the Proposed Rule i
1 A period of 90 days was specified in the Federal Register I
for public comments on the proposed rule.
The Commission specifically sought public comments on:
(1) the appropriateness l
of the proposed 0.05 Sv (5 rem) dose limit in new 10 CFR 60.136 2
as the repository design basis for protection of public health f-and safety during accident conditions, and (2) the rationale supporting the proposed 0.05 Sv (5 rem) dose limit.
Ten sets of-l comments were received on the proposed rule from the following W.
j organizations and individuals:
(1) The Clean Water Fund of North 1
Carolina (CWFNC); (2) Mr. Vernon J. Brechin; (3) DOE, Office of Civilian Radioactive Waste Management; (4) EPA, Office of Federal j
j Activities; (5) Nye County, Nevada, Nuclear Waste Repository 1
i Project Office; (6) Virginia Power Company; (7) Nuclear Energy I
Institute (NEI); (8) Environmental Coalition on Nuclear Power (ECNP) ; (9) Wisconsin Electric Power Company; and I
(10) Mr. Marvin I.
Lewis.
i r
The principal issues raised in the comments are summarized i
below.
(Comments that are duplicative, editorial, or beyond the 1
scope of the rulemaking are not discussed herein but have been i
considered in the analysis of the public comments.)
For the a
k 5
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a i
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seemed to indicate that multiple independent failure scenarios would be considered to be Category 2 design basis events and observed that, typically, nuclear safety analyses are not i
required to assume multiple failures of safety-related systems unless they are all credible consequences of the initiating event.
DOE recommended that the Commission clarify how it intends to review the acceptability of repository systems,
~
structures, and components in the context of the new rule.
The Commission agrees with this comment and has revised the supplementary _information to clarify'how it intends to review the analysis in the DOE license application to demonstrate compliance with the requirements of S60,136.
3.
Probability Bounds for Desian Basis Events.
In the Section-by-Section Analysis of S60.136 in the proposed rule, the Commission indicated that the lower bound for Category 2 design basis events is on the order of 1 x 10" per year (i.e., events with probabilities of occurrence less than 1 x 10" per year would generally be screened from further consideration due to their negligible contribution to overall risk).
DOE and NEI objected that this lower bound is much too low and unjustified.
DOE recommended a lower bound of 1 x 10-' per year and NEI recommended a lower bound in the range of 1 x 10-' per year to 1 x 10" per year.
On the other hand, ECNP 7
- - ~. - -.. -. -. - - - -. ~ _. - -. - - -. -.
reasons-indicated, the Commission has decided to adopt the amendments substantially in the form proposed in the March 22, 1995, Federal Register notice (60 FR 15180) but with the changes l
noted that reflect the Commission's analysis of.the public comments.
- 1. Controlled Area - Waste Isolation.
1 DOE noted that the supplementary information in the proposed rule referred to the " controlled area" as one "... (within which f
waste isolation is to be ensured after permanent closure)," DOE observed that this is inconsistent with the Part 60 definition of i
" controlled area," which does not refer to waste isolation.
DOE recommended that the Commission delete the parenthetical phrase in the supplementary information.
The Commission agrees that the parenthetical phrase does not i
properly characterize the definition of " controlled area."
However, rather than deleting the parenthetical phrase altogether, the Commission has modified the phrase to accurately reflect the definition of " controlled area" and its focus on postclosure activities.
2.
Multiole Failure Scenarios.
DOE noted that the supplementary information under 560.136 6
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recommended that the most improbable sequenceu and combinations of events and accidents (Category 2 and beyond) should be evaluated in repository accident analysis.
I The Commission agrees with DOE and NEI that the lower j
probability bound discussed in the proposed rule for Category 2 design basis events is too-low and is unjustified.
The Commission considers that, on the basis of repository risk perspective, a lower probability bound of 1 x 10-' per year is appropriate for these events.
The Commission recognizes that the estimated consequences from Category 2 design basis events are somewhat limited and would not likely exceed several tenths of Sv (several tens of rem).
At this consequence level, the estimated risk of cancer fatality from events with a probability lower than 1 x 10-' per year is less than 1 x 10-' per year.
To put this risk in perspective, the International Commission on Radiological notes that a fatal cancer risk in the range of Protection 2 1 x 10-' to 1 x 10" per year from exposure to radiation would likely be acceptable to members of the public.
As such, Category 2 design basis events which result in fatal cancer risks on the order of 1 x 10-5 per year or lower do not contribute significantly to individual risk.
Accordingly, events with i
probabilities of occurrence lower than 1 x 10-' per year can be screened from further consideration in repository risk analysis.
Recommendations of the International Commission on Radiological 3
Protection.
ICRP Publication 26, January 1977.
8 l
l
The Commission has revised the Section-by-Section Analysis of S60.136 to reflect a lower bound for Category 2 design basis l
events on the order of 1 x 10-' per year.
l I
4.
Definition of "Imoortant to Safetv" - Engineered t
Eeatures.
{
DOE noted that the phrase " engineered structures, systems, i
and components," currently in the definition of "important to safety," was removed from the new definition and observed that it 1
is clearly the intent of the regulation to apply the definition to engineered systems, not natural systems.
l The Commission agrees with this comment and has revised the definition of "important to safety" to clarify this intent.
(
5.
Anolicability of Environmental Protection Agency Standards to the Manaaement and Storace of Hich-Level Waste.
DOE stated that the proposed rule did not address all of the regulatory uncertainty associated with dose limits for design basis events because both the existing rule and the proposed rule appear to require compliance with both EPA-radiation protection standards and Part 20 radiation standards and there is an inconsistency between these two standards.
Virginia Power noted 9
=
that the definition of "important to safety" establishes the Part 20 limits that are referenced in 10 CFR 60.111(a) as the acceptance criteria for the Category 1 design basis events and concluded that this seems to be inappropriate.
Virginia Power stated that Part 20 establishes occupational dose limits and radiation dose limits for members of the public, that these limits are expressed as annual limits, and that these limits are l
associated with normal licensed activities - not design basis events.
Virginia Power considered that it is not appropriate to f
l use Part 20 limits to evaluate specific events.
Virginia Power I
further considered that acceptance criteria for design basis events are associated with the specific consequences of those events, as for example in S60.136 for the Category 2 design basis events, and that appropriate acceptance criteria will need to be developed if Category 1 design basis events are retained by the final rule.
1 The Commission agrees with DOE that both the dose limits and the methodology for calculating doses to members of the public in the EPA standards differ from the dose limits and methodo;'T/ for calculating doses to members of the public in Part 20, Subpart D.
Notwithstanding the differences between these standards, the staff does not consider that there is any regulatory uncertainty regarding applicable dose limits for Category 1 design basis i
events.
In DOE's demonstration of compliance, either the EPA standards or the Part 20 standards may be more limiting or 10
I controlling than the other, but that does not relieve DOE of the i
requirement to comply with both standards.
As such, the Commission has made no changes to the proposed rule to address DOE's concerns about the differences between Part 20 and the EPA standards.
The Commission disagrees with Virginia Power that Part 20 limits are inappropriate.
The Commission's numerical radiation protection standards are codified in Part 20 and apply to operations at a geologic repository by virtue of 10 CFR 20.1002 and 560.111(a).
However, it is not the Commission's intent that it is necessary to use the annual limits in Part 20 to evaluate specific Category 1 design basis events on an individual basis.
Instead the Commission intends that the Eum of the annual doses, exposures, and releases from all Category 1 design basis events shall not exceed the limits specified in Part 20 and in the EPA standards.
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1 6.
Preclosure Controlled Area.
DOE expressed a concern that the use of the word "l
' "immediately" in the definition of "preclosure controlled area" could lead to an implication that the boundary must be next to the GROA.
DOE also expressed a concern that the use of the word
...no individual located on or
" nearest" in S60.136(b)
(i.e.,
beyond the nearest boundary of the prec)osure controlled 11
)
l
.-=..-
t area...") is confusing.
The Commission agrees with these comments and has:
(1) deleted the word "immediately" in the definition of "preclosure controlled area" in 10 CFR 60.2, (2) changed the phrase " nearest boundary" to "any point on the boundary" in the l
definition of "important to safety" in 560.2 and in the design requirements of the geological repository operations area in 560.136(b).
7.
Definition of Site.
DOE recommended that the definition of " site" should include "preclosure" and "postclosure controlled areas."
The Commission agrees with this comment and has modified the definition of " site" to reflect its meaning during the period before permanent repository closure (i.e.,
the operational period), as well as the period following permanent closure.
8.
Effluent Control.
DOE stated that, with the deletion of the term "during normal operations," the application of the Part 20 effluent limits invoked by S60.111(a) is not clear.
DOE recommended that 10 CFR 60.132 (c) (1) be revised to clarify that the latter section 12
I is applicable only tu Category 1 design basis events.
t l
The Commission agrees with this comment and has revised 560.132 (c) (1) to clarify that this section is applicable only to Category 1 design basis events.
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9.
Criticality Control.
l DOE noted that the Commission intended to clarify the l
j requirements pertaining to criticality control, currently in 10 CFR 60.131(b) (7), but that some confusion concerning those requirements remains.
DOE pointed out that the proposed criticality control requirements in S60.131(h) refer to
" isolation of radioactive waste," a phrase with postclosure f
connotations, while noting that systems "must be designed for criticality safety assuming occurrence of design basis events," a phrase which has preclosure implications.
Furthermore, DOE l
argued that the last sentence in 560.131(h) could be interpreted as requiring a deterministic demonstration of criticality safety l
l over the entire period of regulatory concern.
However, given the l
t time frames involved, DOE considered probabilistic analyses to be j
an essential part of demonstrating long-term criticality safety.
The Commission considers that the applicability of the criticality control requirements proposed in S60.131(h) is clear with respect to preclosure considerations but agrees with DOE i
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i-that uncertainty remains with respect to the applicability of the criticality control requirements to the postclosure period.
i However, the Commission intends to address this remaining uncertainty in a future rulemaking to make the NRC requirements consistent with the revised EPA standards that are currently under development, as mandated by the Energy Policy Act of 1992.
Accordingly, in this final rule, S60,131(h) is promulgated, as proposed in the proposed rule.
10.
The Use of the terms "Imoortant to Safety."
" Accidents." " Normal Conditions "
"Anticioated i
Ocerational Occurrences," and "Desion Basis Events" in Part 60.
CWFNC stated that there was not any ambiguity in the current use of the terms "important to safety" and " accidents"'in i
Part 60.
ECNP stated that the terms " normal conditions,"
" anticipated operational occurrences," and " accidents" are not equivalent to nor adequately described by the term " design basis i
events."
The Commission disagrees with CWFNC that there is no ambiguity in the current use of the terms "important to safety" or " accidents" in Part 60.
The latter term is undefined in Part 60, and there is uncertainty about its meaning with respect to the range of events the term encompasses.
The full range of 14
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Category 1 design basis events would not generally be considered as " accidents," especially those events occurring regularly or moderately frequently.
However, certain lower frequency Category 1 events, which occur one or more times during the operating lifetime of a facility and are otherwise known as
" anticipated operational occurrences," have at times been identified as " accidents."
But " anticipated operational occurrences" are conditions of normal operation which are not to be confused with the unlikely, but credible and potentially significant, Category 2 design basis events.
As such, the current definition of "important to safety" is unclear with respect to its intended applicability to the design of structures, systems, or components for normal operations, including anticipated operational occurrences.
Further, with the 4
focus on protection of members of the public in unrestricted areas, the current definition of "important to safety" does not explicitly address protection for the occupational work force.
The uncertainty is not related to interpreting the meaning of
" unrestricted area" but, rather, is related to the narrow focus of public exposure in unrestricted areas.
Lastly, the value of 0.005 Sv (0.5 rem) as a dose limit in unrestricted areas for
" accident" conditions lacks consistency with a corresponding j
1 limit in Part 72 and with dose values established as guidance for 1
I selected accidents (fuel handling and cask drop events) at Part 50 facilities (commercial power reactors).
I 15
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l accident analyses for more than undefined " critical design 1
basis events, singly" and should require demonstration that doses would be kept far below the maximum permissible dose i
limits, with an as low as is reasonably achievable requirement at least comparable with that for operating reactors.
1 e
The Part 60 limits must be much more stringent than for I
operating nuclear facilities, f
The limit of radiation exposure should be no higher than the a
most restrictive exposure limit that EPA imposes for any i
licensee or other source of regulated nuclear activity.
e A 0.005 Sv (0.5 rem) limit should be impermissible for an individual dose from a waste site.
The most stringent level of worker protection, better than Part 20, should be required.
Part 20 standards are not restrictive enough for the purpose of public health protection with respect to the storage and disposal of radioactive waste, e
The definitional alteration of the term "important to
~
safety" is not adequate to assure health protection for the public because the proposed Categories 1 and 2 numerical limits for radiation exposures are based on standards that have failed to take into account the noncancer but adverse health effects of chronic low-dose radiation exposures that have been reported in the literature since development of NRC's Part 20 revision.
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Notwithstanding the comments offered by ECNP, the Commission considers that the definition of " design basis events" in the proposed rule does adequately define that-term and that the supplementary information in the proposed rule does adequately describe the relationship between the terms " normal conditions,"
" anticipated operational occurrences," " accidents," and " design basis events."
In this regard, it was the Commission's intent to supplant undefined terms in the rule (i.e.,
" normal conditions,"
" anticipated operational occurrences," and " accidents") with a defined term (i.e., " design basis events").
For the above reasons, the Commission has not revised the definitions in the proposed rule for " design basis events."
As j
discussed in items 4 and 6 above, editorial changes have been made to the definition of "important to safety," but these changes are unrelated to the arguments advanced by CWFNC or ECNP.
11.
Radiation Protection Standards.
CWFNC stated that a 0.005 Sv (0.5 rem) limit would not be overly protective of public health and safety and there is no reason to seek a weaker standard.
CWFNC suggested modifying Part 20 to clarify any ambiguities in radiation protection standards for repositories.
ECNP offered a number of comments related to radiation protection standards:
The Commission should require DOE to provide design basis i
i 16
J Extremely conservative radiation protection standards should be utilized in repository design and performance criteria, and a zero release facility design goal should be required for all radioactive waste management.
An acceptable rationale for the 0.05 Sv (5 rem) dose limit o
proposed in the proposed rule is totally absent.
l The Commission' acknowledges that the 0.005 Sv (0.5 rem) dose limit in the definition of "important to safety" in the existing rule could be construed to be an implicit basis for designing structures, systems, and components to prevent or mitigate the
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consequences of accidents at the boundary of the unrestricted area.
On the other hand, the 0.005 Sv (0.5 rem) dose limit could i
i also be interpreted more narrowly, to identify only those structures, systems, and components that are subject to additional design requirements and a quality assurance program to ensure performance of intended functions.
See S60.'.31(b) and S60.151.
In short, the 0.005 Sv (0.5 rem) dose limit in the definition of "important to safety" in the existing rule is, in the Commission's view, subject to conflicting interpretations.
As previously discussed, the Commission's comprehensive review of Part 60 identified deficiencies in both the clarity and sufficiency of requirements to protect workers and public health t
and safety.
Among the identified deficiencies is the regulatory uncertainty created by possible conflicting interpretations that 18
4 i
i could be given to the 0.005 Sv (0.5 rem) dose limit in the "important to safety" definition described above and by the absence of an explicit design basis dose limit in Subpart E of f
the existing rule.
An objective of this rulemaking is, 1
1 therefore, to resolve the uncertainty in Part 60, as well as remedy the incomplete definition of "important to safety" that fails to address protection of both workers and members of the
_public during Category 1 design basis events (i.e.,
" normal conditions," including " anticipated operational occurrences").
.The Commission has addressed these deficiencies with the addition of new S60.136, which now provides explicit design basis accident dose criteria for repository structures, systems, and components,.
and modification of the definition of "important to safety" to include the broader interests of both worker and public health and safety for the full range of conditions or events that may occur before repository closure.
The Commission believes that these anendments, as well as the others as described herein, clarify and enhance the provisions in the rule to protect worker and public health and safety.
It was not the intent of this rulemaking to modify, in any way, the Commission's numerical radiation protection standards.
As discussed earlier, these standards are codified in Part 20 and apply to operations at a geologic repository by virtue of S20.1002, as well as S60.111(a).
The Commission believes that these standards continue to be appropriate for its licensees and 19