[Federal Register Volume 74, Number 15 (Monday, January 26, 2009)]
[Proposed Rules]
[Pages 4346-4353]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E9-1211]
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Proposed Rules
Federal Register
________________________________________________________________________
This section of the FEDERAL REGISTER contains notices to the public of
the proposed issuance of rules and regulations. The purpose of these
notices is to give interested persons an opportunity to participate in
the rule making prior to the adoption of the final rules.
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Federal Register / Vol. 74, No. 15 / Monday, January 26, 2009 /
Proposed Rules
[[Page 4346]]
NUCLEAR REGULATORY COMMISSION
10 CFR Part 50
[NRC-2007-0016; PRM-50-87]
Raymond A. Crandall; Denial of Petition for Rulemaking
AGENCY: Nuclear Regulatory Commission.
ACTION: Denial of petition for rulemaking.
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SUMMARY: The Nuclear Regulatory Commission (NRC) is denying the
petition for rulemaking (PRM) filed by Mr. Raymond A. Crandall on May
17, 2007, and docketed on June 22, 2007 (Docket No. PRM-50-87). In his
petition, the petitioner requested that the NRC amend the regulations
that govern domestic licensing of production and utilization facilities
to eliminate the specific criteria related to the radiological doses
for control room habitability at nuclear power plants. The petitioner
stated that the current deterministic radiological dose requirements
for control room habitability have resulted in several negative safety
consequences, including an increased risk to public safety. He
requested that the NRC delete the 5 rem whole body dose limit and the
0.05 sievert (Sv) (5 rem) total effective dose equivalent (TEDE) limit
specified in the current regulations.
DATES: The docket for PRM-50-87 is closed as of January 26, 2009.
ADDRESSES: Publicly available documents related to this petition,
including the PRM and the NRC's letter of denial to the petitioner may
be viewed using the following methods:
Federal e-Rulemaking Portal: Go to http://www.regulations.gov and
search for documents related to this PRM filed under docket ID NRC-
2007-0016.
NRC's Public Document Room (PDR): The public may examine publicly
available documents and have them copied for a fee at the NRC's PDR,
Public File Area O-1 F21, One White Flint North, 11555 Rockville Pike,
Rockville, Maryland.
NRC's Agencywide Document Access and Management System (ADAMS):
Publicly available documents created or received at the NRC are
available electronically via the NRC's Electronic Reading Room at
http://www.nrc.gov/NRC/reading-rm/adams.html. From this page, the
public can gain entry into ADAMS, which provides text and image files
of the NRC's public documents. If you do not have access to ADAMS or
have any problems in accessing the documents located in ADAMS, contact
the NRC PDR Reference staff at 1-800-397-4209, or 301-415-4737, or by
e-mail to [email protected].
FOR FURTHER INFORMATION CONTACT: A. Jason Lising, Office of Nuclear
Reactor Regulation, U.S. Nuclear Regulatory Commission, Washington, DC
20555-0001, telephone: (301) 415-3220, or toll-free: 800-368-5642; e-
mail: [email protected].
SUPPLEMENTARY INFORMATION:
I. Background
II. Petitioner's Requests
III. Reasons for Denial
IV. Public Comments
V. Denial of Petitions
I. Background
On May 17, 2007, the NRC received a PRM from Raymond A. Crandall
(ADAMS Accession No. ML071490250); the PRM was docketed by the NRC as
PRM-50-87. The petitioner requested that the NRC amend Title 10 of the
Code of Federal Regulations Part 50 (10 CFR Part 50), ``Domestic
Licensing of Production and Utilization Facilities'' to remove the
specific criteria related to the radiological doses for control room
habitability at nuclear power plants from 10 CFR 50.67, ``Accident
source term,'' and General Design Criterion (GDC) 19, ``Control room,''
in Appendix A, ``General Design Criteria for Nuclear Power Plants,'' to
10 CFR Part 50. The NRC published a notice of receipt and request for
public comment in the Federal Register on July 12, 2007 (72 FR 38030).
The 75-day public comment period ended on September 25, 2007.
The petitioner noted that the current regulations provide specific
dose criteria for demonstrating the acceptability of the control room
design during radiological release events. These criteria are based on
deterministic radiological dose analyses performed by the licensee and
reviewed by the NRC. NRC regulatory guides and standard review plans
provide acceptable methodologies that can be used by licensees to
perform dose analyses, which are then incorporated, as appropriate,
into the licensing basis for the licensee's facility. The petitioner
stated that the deterministic dose analysis methodology and associated
regulatory process result in several negative safety consequences:
(1) Current Designs Not Optimum
``Control room designs that are not optimum for ensuring continued
control room habitability. Current designs required in order to meet
the current dose methodology criteria may actually increase the
probability of having to evacuate the control room compared to
establishing the design based on good engineering principles.''
(2) Procedures Not Optimized
``Site procedures for mitigation of the dose consequences to
control room personnel that are not optimum for ensuring control room
habitability. The procedures designed to ensure consistency with the
dose analysis assumptions are inconsistent with more effective
mitigation strategies.''
(3) Challenges to Safety Systems
``Unnecessary challenges to safety systems, such as increased
challenges to the Emergency Diesel Generators if control room
ventilation system fans are loaded on the diesels early in the accident
to meet analysis assumptions.''
(4) Inappropriate Technical Specification (TS) Action Statements
``Technical Specifications Action Statement requirements that
result in a net increase in the risk to the public. This specifically
refers to Technical Specifications that require a plant shutdown for
failure to meet a control room dose analysis input assumption.''
(5) Unjustified Technical Specification Surveillances
``Technical Specifications Surveillance requirements that cannot be
cost-justified based on the risk-significance. This results in the
required expenditure of resources that could be used on risk-
significant improvements.''
The petitioner suggested amendments that would eliminate the
specific radiological dose acceptance criteria and, thereby, the need
for deterministic dose analyses and the associated regulatory
processes, including the need for applicable TSs. He stated that the
[[Page 4347]]
proposed changes would not eliminate the requirement for the control
room to be designed to ensure safe conditions under accident
conditions, but it would address his safety concerns with the current
regulations.
II. Petitioner's Request
In PRM-50-87 the petitioner requested that the NRC take the
following actions:
1. Revise the regulations related to control room habitability at
nuclear power plants by deleting the following sentences from GDC 19:
``Adequate radiation protection shall be provided to permit access
and occupancy of the control room under accident conditions without
personnel receiving radiation exposures in excess of 5 rem whole body,
or its equivalent to any part of the body, for the duration of the
accident. Applicants for and holders of construction permits and
operating licenses under this part who apply on or after January 10,
1997, applicants for design certifications under part 52 of this
chapter who apply on or after January 10, 1997, applicants for and
holders of combined licenses under part 52 of this chapter who do not
reference a standard design certification, or holders of operating
licenses using an alternative source term under Sec. 50.67, shall meet
the requirements of this criterion, except that with regard to control
room access and occupancy, adequate radiation protection shall be
provided to ensure that radiation exposures shall not exceed 0.05 Sv (5
rem) total effective dose equivalent (TEDE) as defined in Sec. 50.2
for the duration of the accident.''
2. Revise the regulations related to control room habitability at
nuclear power plants to delete from paragraph (b)(2)(iii) in 10 CFR
50.67 this language:
``Adequate radiation protection is provided to permit access to and
occupancy of the control room under accident conditions without
personnel receiving radiation exposures in excess of 0.05 Sv (5 rem)
total effective dose equivalent (TEDE) for the duration of the
accident.''
III. Reasons for Denial
1. General
The NRC has reviewed Mr. Raymond Crandall's petition and has
determined that it does not provide adequate justification to remove
the control room radiological dose acceptance criteria from NRC
regulations. The NRC does not agree with the petitioner's assertion
that the control room radiological dose acceptance criteria have
resulted in negative safety consequences.
Performance-based regulations, such as Sec. 50.67 and Appendix A
to 10 CFR Part 50, do not provide prescriptive requirements and,
therefore, do not require licensees to use specific designs or
methodologies to comply with the regulations. The NRC, however, does
provide regulatory guidance to licensees that includes acceptable
designs and methodologies for demonstrating compliance with the
regulations. The use of the guidance is optional, and licensees are
free to propose alternative means of complying with the NRC's
regulations.
Design-basis dose consequence analyses are intentionally based upon
conservative assumptions and are intended to model the potential
hazards that would result from any credible accident, not necessarily
the most probable accident. As stated in footnotes to 10 CFR 100.11,
``Determination of exclusion area, low population zone, and population
center distance,'' and 10 CFR 50.67, ``Accident source term,'' ``[t]he
fission product release assumed for these calculations should be based
upon a major accident, hypothesized for purposes of site analysis or
postulated from considerations of possible accidental events, that
would result in potential hazards not exceeded by those from any
accident considered credible. Such accidents have generally been
assumed to result in substantial meltdown of the core with subsequent
release of appreciable quantities of fission products.''
The performance-based control room dose criterion is designed to
maintain an acceptable level of control room habitability even under
the maximum credible accident scenario. The NRC has determined that
providing an acceptable level of control room habitability for design-
basis events is necessary to provide reasonable assurance that the
control room will continue to be effectively manned and operated to
mitigate the effects of the accident and protect public health and
safety. Meeting or exceeding the design-basis control room dose limit
would not impose an immediate evacuation requirement on the control
room operators. Moreover, by removing the 5 rem acceptance criterion, a
regulatory basis for the acceptance of the radiological protection
aspects of control room designs would no longer exist and would not
support the Commission's policy regarding performance-based
regulations.
The conservative assumptions used in design-basis dose consequence
analyses need not and should not form the basis for restricting actions
described in emergency operating procedures. These procedures are
designed to ensure that during an accident all available means are used
to assess actual radiological conditions and to maintain emergency
worker doses As Low As Reasonably Achievable (ALARA), as required by 10
CFR Part 20, ``Standards For Protection Against Radiation.''
Additionally, no NRC regulations, including 10 CFR Part 20, ``Standards
for Protection Against Radiation,'' require evacuation of the control
room when the design-basis control room dose limit is exceeded.
Emergency operating procedures include guidance for controlling doses
to workers under emergency conditions. This guidance would be
applicable in the unlikely event that control room doses were projected
to exceed the design-basis dose limit during an actual emergency.
2. NRC Staff Responses to the Petitioner's Assertions
A. Current Designs Are Not Optimum
1. The petitioner stated that because the primary objective of
control room habitability is to ensure continuous occupancy, the
primary focus should be on minimizing whole body doses from noble
gases. He stated that some common control room designs, such as the
filtered air intake pressurization design, focus on compliance with
existing dose criteria. He concluded that the current requirements and
operational criteria focus on minimizing the thyroid dose at the
expense of increasing the whole body dose from noble gases which
increases the probability that the control room will require
evacuation.
The NRC reviewed the petitioner's concern regarding the increase in
whole body dose from noble gases, which he believes results from the
intentional intake of filtered air into the control room under design-
basis accident (DBA) conditions. The NRC agrees that a relatively small
increase in whole body dose due to noble gases may result from the
intake of filtered air into the control room. However, this small
increase in dose would not increase the probability of a control room
evacuation. Therefore, operators would be able to monitor plant
indications and take appropriate accident mitigating actions from the
control room, and there would be no increase in risk to public health
and safety. The NRC's conclusion is based on a review of several
existing DBA control room dose analyses that determined the impact on
whole body dose resulting from filtered air intake pressurization to
the control room. The NRC performed parametric evaluations and
determined that while filtered air
[[Page 4348]]
intake pressurization may result in a small addition to the control
room whole body dose from noble gases, the increase is more than offset
by the reduction in thyroid dose and TEDE from inhalation of
radioactive particulates, such as iodine.
Based upon its analyses, the NRC does not agree with the
petitioner's assertion regarding the negative safety impact of
providing filtered intake flow into the control room. The NRC's
performance-based criterion in GDC 19 requires that an applicant
provide a control room habitability design that meets the specified
dose criterion. Although NRC regulatory guidance provides examples of
acceptable design approaches, the approach used to meet the criterion
is largely under the control of an applicant. In order to meet this
requirement, many licensees have chosen to incorporate filtered air
intake pressurization into their control room emergency ventilation
designs to reduce the cumulative dose to operators during a DBA. The
purpose of providing filtered air intake pressurization flow is to
establish positive pressure in the control room relative to the
adjacent areas, thereby reducing the quantity of unfiltered air
inleakage. Limiting unfiltered inleakage significantly reduces the
thyroid dose from inhalation.
2. The petitioner also stated that the current regulation is
inconsistent with the goal of allowing operators to remain in the
control room in order to mitigate accident consequences. He stated that
common designs, such as a filtered air intake pressurization system,
which focus on compliance with existing criteria, increase the
probability that the control room will have to be evacuated.
The 5 rem control room design criterion is not a maximum integrated
dose above which control room evacuation is mandated during an
accident. Rather, the criterion provides a design basis to ensure that
the control room will maintain a habitable environment for operators to
control the plant during a DBA.
The petitioner based his assertion on the assumption that
filterable activity is not likely to be a significant contributor to
dose in a reactor accident. As an example, the petitioner used the
March 1979 Three Mile Island Unit 2 accident. Since the accident, the
NRC has expended considerable resources to better define the expected
quantity and distribution of activity that could be released during a
major reactor accident. As a result of this research, the NRC
promulgated 10 CFR 50.67 on December 23, 1999 (64 FR 72001). Under 10
CFR 50.67, a licensee can apply for a license amendment to adopt an
alternative source term (AST) that reflects a more realistic assessment
of the timing of the release and the quantity and distribution of
activity that could be released during a major accident hypothesized
for purposes of design analyses. Many licensees have used this approach
to comply with NRC regulations governing control room dose.
In addition, 10 CFR 50.67 revised the control room dose criterion
from a 5 rem whole body dose, or its equivalent to any organ, to a 5
rem TEDE. The relatively low thyroid organ weighting factor, as defined
in 10 CFR 20.1003, ``Definitions,'' and used in the calculation of
TEDE, allows for a significant reduction in the controlling aspects of
the thyroid dose, which normally governed compliance with control room
dose guidelines. The NRC has significantly improved the accuracy of the
source term and dose methodology used in design-basis dose consequence
analyses. The updated source term and dose methodology address the
petitioner's concerns regarding the emphasis on thyroid dose in control
room habitability analyses.
3. The petitioner noted that the dose from increased iodine
concentration can be mitigated by use of potassium iodide (KI) or
respiratory protection, but the current regulations do not permit these
mitigation measures to be used in design analyses.
The NRC agrees that KI or Self-Contained Breathing Apparatuses
(SCBAs) do have merit as short-term compensatory measures. However, the
potential medical complications of KI and the potential adverse impacts
to human performance of SCBAs make these measures unsuitable for long-
term use. Further, the NRC's policy of ensuring that process or other
engineering controls are in place instead of relying on the use of
personal protective equipment is clearly set forth in 10 CFR 20.1701,
``Use of process or other engineering controls'' and 10 CFR 20.1702,
``Use of other controls.'' This policy is consistent with the
recommendations of international and national radiation protection
committees as described in Paragraph 167 of the International
Commission on Radiological Protection (ICRP) Publication 26.
Paragraph 167 of ICRP Publication 26 recommends that ``[a]s far as
is reasonably practicable, the arrangements for restricting
occupational exposure should be applied to the source of radiation and
to features of the workplace. The use of personal protective equipment
should in general be supplementary to these more fundamental
provisions. The emphasis should thus be on intrinsic safety in the
workplace and only secondarily on protection that depends on the
worker's own actions,'' such as the ingestion of KI or use of
respiratory equipment. Further, the use of respiratory equipment by
control room personnel during an emergency condition would impede the
performance of functions necessary for the protection of public health
and safety. Therefore, the NRC has not permitted licensees to rely on
either KI or respiratory protection as a permanent solution to
demonstrate compliance with the control room radiological dose
guidelines, although such measures are available if the fundamental
dose design provisions are less effective than anticipated.
4. The petitioner stated that it is inconsistent to provide credit
for respiratory protection in control room habitability toxic gas
release evaluations, but not for design analyses.
The NRC does not agree with the petitioner. In the case of toxic
gas releases, continued plant operation or a normal plant shutdown
would be required. In the case of a major reactor accident involving
radiological releases, control room personnel must implement extensive
emergency operation procedures to ensure public health and safety.
Wearing respiratory protection during normal operations or even during
an orderly shutdown, should it be necessary as a result of a toxic gas
release, would not be expected to present significant challenges to
control room personnel equivalent to those present during a reactor
accident. The NRC is reluctant to place any more of a burden than is
absolutely necessary on control room personnel, who would already be
significantly tasked ensuring that all emergency procedures are carried
out without error.
B. Procedures Are Not Optimized
The petitioner stated that control room dose mitigation procedures
must be consistent with the licensing basis and may not be the optimum
mitigation strategy for more likely conditions. For example, he stated
that control room dose models do not model dispersion as a period
during the day with higher concentrations while the plume is blowing
towards the control room and then a period of zero concentration for
the rest of the day. Instead, analysis methods simplify this effect by
assuming that a lower concentration is present continuously. The
petitioner claimed that if procedures were revised to include a control
room purge mode
[[Page 4349]]
strategy, a ``calculated increase in consequences in the simplistic
design basis analysis'' would result.
The NRC disagrees with the petitioner. The NRC's regulations do not
require that procedures be limited to the most limiting licensing-basis
assumptions. Further, the NRC expects licensees to develop procedures
that address the full-scope review of design-basis events and
conditions.
With respect to the petitioner's example, procedures to operate the
control room in its design-basis mode must be provided. These
procedures do not preclude licensees from creating additional
procedures to purge the control room if warranted by plant conditions.
Licensees are permitted to develop and implement such procedures under
existing NRC regulations.
The NRC agrees that control room purging may be a reasonable action
during a reactor accident when the level of outside airborne
concentration of radioactive material is less than the level inside the
control room. However, the conditions favorable for control room
purging cannot be predicted, and the NRC cannot credit control room
purging in the DBA analysis unless the timing of the release can be
accurately established. For accidents where NRC regulatory guidance has
established the release duration, the NRC has accepted credit for
control room purging after the release has ended. As a design
criterion, GDC 19 does not supplant the radiation protection standards
of 10 CFR Part 20, which treat the radiation exposure of control room
operators as occupational exposure. Therefore, the NRC expects
licensees to maintain the accumulated dose of their radiation workers
ALARA. During an accident, health physics personnel would monitor the
radiological conditions in the control room and other emergency
response facilities. These health physicists are responsible for making
appropriate recommendations to plant personnel on actions that can be
taken to maintain the dose to emergency responders ALARA.
C. Challenges to Safety Systems
The petitioner stated that the current design requirements, which
are usually imposed to ensure the assumptions of the dose analysis are
met, may not be optimum from an overall risk perspective. As an
example, he stated that a common design requirement specifies that the
normal control room ventilation must isolate on receipt of a safety
injection or containment isolation signal during an assumed loss-of-
coolant accident. The petitioner stated that it is more logical to
delay control room isolation until radioactivity is detected in the
control room or it is known that a radioactive plume is blowing towards
the control room. The petitioner suggested that mitigating design
strategies should be based on overall risk reduction designed for more
likely conditions, not on one unlikely set of fixed hypothetical
conditions.
The NRC does not agree with the petitioner. Contrary to the
petitioner's assertion, the NRC's regulations do not require immediate
control room isolation or immediate appearance at the control room
intake of the radioactive plume assumed in design-basis dose
consequence analyses. The NRC has approved, in accordance with its
regulations, plant designs that do not immediately isolate the control
room ventilation system. Further, design bases that include the
immediate startup of control room ventilation systems and loading of
electrical buses and diesel generators with this equipment do not
require operation of plant systems beyond their design capabilities;
the diesels are specifically designed and sized to accommodate these
safety loads. Therefore, the performance of these systems should not be
impacted, and there is no increased risk to public health and safety.
D. Inappropriate Technical Specification Action Statements
The petitioner stated that the conservative nature of the current
radiological dose mitigation analyses also results in inappropriate TS
action statements. He stated that ``there is insignificant safety
significance to the TS associated with control room habitability and
yet there are shutdown requirements.'' The petitioner believes that in
order to evaluate the net public safety risk associated with these TS
shutdown requirements, small but quantifiable public risks associated
with the shutdown of a nuclear power plant must be considered,
including but not limited to the following:
1. Risk associated with bringing the plant through a transient and
another thermal cycle;
2. Airborne pollutants released by the fossil units required to
operate to make up for lost power; and
3. Potential for challenging electric power grid stability with the
public risk associated with the possibility of rolling blackouts or
brownouts or, under the worst conditions of grid instability, the
potential for a loss of offsite power at multiple nuclear power
facilities.
The petitioner claimed that the shutdown requirement increases the
net public risk and should be eliminated because it is only imposed as
a ``matter of compliance.''
The NRC disagrees with the petitioner. The NRC has approved license
amendments to replace TS requirements for an immediate shutdown for an
inoperable control room envelope boundary with requirements for
immediate mitigating actions and restoration of the control room
envelope to operable status within 90 days.
The NRC has determined that none of the regulations proposed to be
changed by the petitioner directly require a plant shutdown in response
to control room habitability issues. Existing NRC regulations permit a
licensee to propose alternative TS action requirements to its plant
shutdown requirements. The NRC notes that even if the petitioner's
proposed regulatory changes were made, licensees would still need to
submit a license amendment to justify changes to their TSs for NRC
approval.
A controlled shutdown and cooldown of a plant is a safe evolution
within the design capability of the plant and would not result in undue
risk to public safety. In the event of unusual circumstances associated
with adverse electrical power grid instability or other complicating
issues that would be associated with a plant shutdown, there are
processes available for a licensee to obtain regulatory relief to
safely continue plant operation (e.g., emergency/exigent technical
specification change, enforcement discretion).
E. Unjustified Technical Specification Surveillances
The petitioner stated that ``individual input assumptions for
radiological dose analyses have no significance in predicting reality
or the acceptability of results. Even if actual conditions were such
that one of the assumptions was non-conservative by a couple orders of
magnitude, the ultimate result (in this case habitability of the
control room) would still be acceptable due to the significant
conservatisms in the other assumptions and the simplicity of effective
mitigating actions such as the use of KI.'' He stated that although
most control room habitability surveillances can be performed with
minimal resources, licensees have been required to demonstrate the
accuracy of the assumption regarding unfiltered inleakage using an
unjustified tracer gas testing method that costs approximately $100,000
per test. The petitioner stated these tests have demonstrated that
although inleakage values assumed in the analyses were nonconservative,
there was no safety significance and continued operation was justified.
The
[[Page 4350]]
petitioner concluded that the expenditure for tracer gas testing could
be better used for improvements that would likely be more beneficial to
plant safety; therefore, the required performance of this test could
have a net negative safety consequence. The petitioner stated that
previous surveillances, such as a pressurization test, combined with
lessons learned from tracer gas testing result in an effective
preventative maintenance program.
The NRC does not agree with the petitioner's assertion that
individual input assumptions for radiological dose analyses have no
significance in predicting reality or the acceptability of results. The
NRC places a high priority on operator safety; the requirements
contained in GDC 19 should be retained because they provide physical
and psychological protection for operators and ultimately for the
general public. Therefore, the data used in the analyses to determine
operator safety should be accurate, and when data are uncertain,
appropriate conservatisms are applied.
The NRC does not agree with the petitioner's statement that the
expenditure for tracer gas testing could be better used for
improvements that would likely be more beneficial to plant safety nor
does the NRC agree that the performance of tracer gas testing could
have a net negative safety consequence. The potential dose to the
operator must be quantified in order to ensure that the requirements of
GDC 19 are met; the specific measurement of inleakage is one of the
inputs to the analyses used to quantify the potential dose to the
operator. Prior to the use of tracer gas to measure inleakage, the
quantity of inleakage was assumed rather than measured and subsequently
found to be nonconservative. Tracer gas testing is justified because it
ensures operator safety. Other methods of measuring inleakage have not
been successfully demonstrated.
F. Petitioner's Proposed Alternatives to Current NRC Guidance
The NRC has decided to deny this petition for rulemaking and would
normally not discuss the petitioner's proposed guidance in this
document. However, in order to clarify the NRC's decision to maintain
the current radiological dose requirements, the following discussion is
provided.
Under Commission policy, the NRC's regulations for control room
habitability provide performance-based requirements to ensure that
plant personnel are adequately protected. The NRC has concluded that
prescriptive requirements or guidance, such as that proposed by the
petitioner, may unnecessarily restrict a licensee's options for
complying with the NRC's regulations.
The petitioner proposed revisions to the NRC's regulatory guidance
to help implement his proposed rule change. NRC regulatory guidance is
not an appropriate subject for a PRM and the NRC will not generally
consider such requests through this process. Further, current NRC
regulatory guidance provides one acceptable mechanism for licensees and
applicants to meet the requirements of the NRC's regulations.
Applicants and licensees may propose alternative means of complying
with the NRC's regulations, which will be evaluated by the NRC staff on
a case-by-case basis.
1. The petitioner recommended that the control room ventilation
system should isolate on the detection of high radiation or toxic
intake. The NRC disagrees with the petitioner. All control rooms are
required by TSs to take appropriate action upon detection of radiation
or toxic gas. Appropriate action may differ from plant to plant
depending on location, design, and TSs. Because plants are unique,
licensees can demonstrate compliance with the control room design
criteria by taking different approaches. The petitioner's suggestion
does not address the long-term release situations that would be
expected under a worst case accident scenario. Control room isolation
alone would not be an acceptable solution because it does not
adequately consider the long term breathing air requirements necessary
to provide a safe working environment in the control room. After a
relatively short period of time, an intake of air into the control room
would be necessary. Licensees include these considerations in their
site-specific control room habitability analyses. Therefore, the NRC
concludes that changing guidance to recommend control room isolation on
detection of high radiation or toxic gas is an unnecessarily
prescriptive recommendation in comparison to the existing performance-
based dose criterion.
2. The petitioner recommended that the control room have a minimum
of one foot of concrete shielding (or equivalent) on all surfaces. The
NRC disagrees with the petitioner. The NRC believes that control rooms
are adequately protected from the effects of direct radiation because
current regulations require that either a 5 rem whole body or a 5 rem
TEDE acceptance criterion be met under DBA conditions. Licensees
include the effects of direct radiation from all potential sources in
their control room dose consequence analyses. Typically these sources
include the following:
Contamination of the control room atmosphere by the intake
and infiltration of the radioactive material contained in the
radioactive plume released from the facility;
Direct shine from the external radioactive plume released
from the facility with credit for control room structural shielding;
Direct shine from radioactive material in the containment
with credit for both the containment and control room structural
shielding; and
Radiation shine from radioactive material in systems and
components inside or external to the control room envelope, including
radioactive material buildup on the control room ventilation filters.
Many control rooms already have one foot or more of concrete
shielding on all surfaces. One foot of concrete shielding does not
guarantee adequate protection from radiation. For example, surfaces
with 1 foot of concrete with penetrations for various equipment, such
as electrical wiring and ventilation ducts, may not provide any more
protection than non-concrete surfaces or surfaces with less than 1 foot
of concrete. To show compliance with the current control room dose
criterion, licensees provide detailed radiological calculations to
ensure that under DBA conditions control room personnel will be
adequately protected. Licensees have demonstrated compliance with the
regulations crediting many different design approaches. The NRC
concludes that recommending that the control rooms have one foot of
concrete shielding is an unnecessarily prescriptive recommendation.
3. The petitioner recommended that because of the low risk
significance of being outside the control room habitability program
guidelines, a plant shutdown should not be required in this condition.
Rather, the petitioner recommended that the program could specify that
timely actions should be taken to return the plant to within the
guidelines. If not complete within 30 days, the petitioner suggested
that a special report would be sent to the NRC with a justification for
continued operations and a proposed schedule for meeting the
guidelines. The NRC disagrees with the petitioner that a regulatory
change is required to permit these changes to plant TSs. The NRC allows
deviations from the integrity of the control room envelope without
requiring an immediate plant shutdown.
4. The petitioner recommended that as an alternative to the total
removal of
[[Page 4351]]
dose guidelines from the regulations, most of his concerns could be
resolved if the dose criteria were based solely on the whole body dose
from noble gases. The NRC does not agree with the proposition that the
dose criteria should be based solely on the whole body dose from noble
gases. The control room dose criterion of 5 rem whole body or its
equivalent to any organ imposes two requirements on licensees:
Satisfaction of the whole body dose criterion, which is generally
dominated by the dose from noble gases; and satisfaction of the organ-
specific dose guidelines, which are generally dominated by the thyroid
dose from the inhalation of iodine. In most cases, demonstrating
compliance with thyroid dose guidelines poses a significantly greater
challenge to licensees than does compliance with the whole body dose
criterion.
The 1999 amendment to 10 CFR 50.67 (64 FR 12117), revised the
control room dose limit to allow licensees to show compliance with
either the existing limits, using the traditional Technical Information
Document (TID)-14844 source term assumptions, or a revised single
control room dose criterion of 5 rem TEDE,\1\ if the licensee adopts
the AST. With the ability to reassess a maximum credible radiological
release using the AST, many licensees have shown compliance with the
Sec. 50.67 single control room dose criterion of 5 rem TEDE. Licensees
have accomplished this while achieving an enhanced degree of
operational flexibility not realized using the traditional TID-14844
source term with the associated whole body dose criterion and organ
dose guidelines. Because compliance with Sec. 50.67 is demonstrated by
calculating the TEDE, the relative contribution of the thyroid dose to
the demonstration of compliance with the control room criterion has
been substantially and appropriately reduced. In addition, many
licensees that continue to use the traditional TID-14844 source term
have incorporated the guidance in Regulatory Guide (RG) 1.195,
``Methods and Assumptions for Evaluating Radiological Consequences for
Design-Basis Accidents at Light-Water Nuclear Power Reactors''
(ML031490640) to achieve operational flexibility. Following the
guidance in RG 1.195, licensees are able to evaluate control room
habitability using a 50 rem thyroid dose guideline. This represents a
significant relaxation from the 30 rem thyroid dose guideline that was
incorporated into previous guidance documents.
---------------------------------------------------------------------------
\1\ As defined in 10 CFR 20.1003, ``Total Effective Dose
Equivalent (TEDE) means the sum of the effective dose equivalent
(for external exposures) and the committed effective dose equivalent
(for internal exposures).'' The effective dose equivalent for
external exposures includes the whole body dose from noble gases.
The committed effective dose equivalent for internal exposure
includes the thyroid dose from inhalation of iodine.
---------------------------------------------------------------------------
The petitioner also stated that the whole body dose from noble
gases is likely to be the only possible dose impact that may result in
control room evacuation. The NRC does not accept the premise that any
maximum credible radiological release would result in the necessity for
a control room evacuation. As stated previously, the 5 rem control room
design criterion is not intended to be a maximum integrated dose level
at which control room evacuation would be mandated during an accident.
Rather, the criterion is used as a design basis to ensure that the
control room, by design, will provide a habitable environment for the
control of the plant under the maximum credible radiological release
conditions, and as such will provide reasonable assurance of adequate
protection.
The petitioner stated that most of his concerns would be resolved
if credit for SCBAs or KI was allowed in the analysis of the dose from
iodines and particulates. The NRC does not agree with the option of
replacing engineering controls for radiological protection with credit
for personal protective equipment. As discussed previously, the option
of allowing credit for SCBAs or KI to show compliance with the control
room performance-based design criterion is inimical to the NRC design
philosophy incorporated into 10 CFR Part 20, as well as international
standards for radiological protection as set forth in ICRP Publication
26.
IV. Public Comments
1. Overview of Public Comments
The NRC's notice of receipt and request for public comment invited
interested persons to submit comments. The comment period for PRM-50-87
closed on September 25, 2007. The NRC reviewed and considered the
comments in its decision to deny the petition. The NRC received two
public comments, one from Mr. Walston Chubb (ML072681072), and one from
Mr. James H. Riley on behalf of the Nuclear Energy Institute (NEI)
(ML072690232).
2. Mr. Walston Chubb Comment
Comment: Mr. Chubb recommended that operators be required to remain
on duty until they are relieved or their short-time doses are between
100 and 200 rem.
NRC Response: The primary objective of GDC 19 is to ensure that the
design of the control room and its habitability systems provide a
``shirt-sleeved'' environment for operators during both normal and
accident conditions. This environment facilitates operator response to
normal and accident conditions while minimizing errors of omission or
commission. Another objective is to ensure that the radiation dose
levels in the control room would make it the safest location on site,
thereby allowing the operators to remain in the control room. Any
reduction in operator accident response capabilities may negatively
impact public health and safety.
The NRC's decision to apply the 5 rem whole body dose criterion was
based on the following:
A whole body radiation exposure of 5 rem is considered
unlikely to cause increased anxiety that would result in operator
impairment, since the criterion is comparable to the occupational dose
limits.
A whole body radiation exposure of 5 rem would not result
in any somatic response that could result in operator impairment.
Generally, the onset of clinically observable somatic effects occurs
between 25 and 50 rem.
GDC 19, as a design criterion, does not supplant the
radiation protection standards of 10 CFR Part 20. The radiation
exposure of control room operators is controlled, as for any radiation
worker at the facility, as occupational exposure under 10 CFR Part 20.
In the statements of consideration for the 10 CFR Part 20 rulemaking
(56 FR 23365; May 21, 1991), the NRC stated that the dose limits for
normal operation should remain the primary guidelines for an emergency.
The statement of considerations in the proposed and final rule
amending 10 CFR 50.67 and GDC 19 (64 FR 12117, March 31, 1999; and 64
FR 71990, December 23, 1999, respectively) included the NRC's basis for
establishing the 5 rem TEDE as the GDC 19 numeric criterion for
licensees applying for amendment under 10 CFR 50.67. It also reaffirmed
the position that the criteria in GDC 19 and the final rule are based
on occupational exposure limits.
The 5 rem control room design criterion is not intended to be a
maximum integrated dose above which control room evacuation would be
mandated during an accident. Rather, the 5 rem design criterion ensures
that the control room, by design, will provide a habitable environment
for the
[[Page 4352]]
control of the plant under all DBA conditions.
Providing a safe working environment for the highly skilled
professionals needed to operate a nuclear power plant is a primary
objective of NRC regulations related to occupational and accident dose,
and it is a paramount goal throughout the entire nuclear power
industry. The NRC concludes that the proposal to set the control room
design criterion at 100 rem, which is well above the level at which the
onset of clinically observable somatic effects would occur, is
antithetical to the fundamental principle of protecting public health
and safety and is not acceptable.
3. NEI Comments
NEI provided the following comments:
Comment: ``It is not so much the value of the exposure limits that
is the problem. The NRC should be more open to other methods of
analysis proposed by licensees. Every Regulatory Guide states that the
guidance is one method acceptable to the staff and that other methods
proposed by licensees will be evaluated on a case-by-case basis.
However, in practice it is often difficult to justify different
approaches.''
NRC Response: To the extent that the comment implicitly criticizes
the NRC for allegedly failing to consider alternatives for compliance
with GDC 19 and 10 CFR 50.67 in a manner other than that suggested in a
regulatory guide, that concern is beyond the scope of this petition for
rulemaking. Further, the commenter presented no basis for this implicit
criticism--the NRC routinely considers licensee and applicant-proposed
alternatives to methods set forth in a Regulatory Guide. However, the
NRC expects licensees and applicants to provide technically sufficient
basis for the use of an alternative for compliance with an NRC
regulation, which is also consistent with the regulatory policies of
the NRC. That a licensee or applicant may find it difficult to provide
sufficient basis justifying the use of an alternative approach,
however, would not appear to present a valid regulatory concern.
Comment: Existing emergency filtration systems should be maintained
to practical performance criteria. NEI stated that this area has a lot
of potential for improvement and gave the following examples:
The current practice (i.e., RG 1.52, ``Design, Inspection,
and Testing Criteria for Air Filtration and Adsorption Units of Post-
Accident Engineered-Safety-Feature Atmosphere Cleanup Systems in Light-
Water-Cooled Nuclear Power Plants'') (ML011710176) is to apply a safety
factor of 2 for laboratory testing of charcoal beds. The actual
efficiencies are typically much higher than those allowed by RGs.
Some plants have an 8-inch charcoal bed, for which only 4
inches is allowed to be credited.
Other plants have filtration systems in series, for which
only one composite filter can be credited.
NRC Response: The NRC's position on existing emergency filtration
systems is outlined in RG 1.52, Revision 3, issued June 2001. The
previous revision of the RG included a safety factor as great as 7
whereas Revision 3 includes a safety factor of 2 to account for
degradation of the system between test periods. A safety factor
represents margin in the capability of the adsorbent (carbon) installed
in the system to perform the required safety function. Because carbon
can degrade between test periods, a safety factor provides confidence
that the anticipated degradation will not be beyond the minimum level
necessary to perform its required safety function.
RG 1.52, Revision 3, indicates that a 4-inch carbon bed in U.S.
nuclear power plants is 99 percent efficient, with a safety factor of 2
and a penetration (as defined in American Society for Testing and
Materials D 3803-89) of less than or equal to 0.5 percent. The NRC
believes that a 4-inch carbon bed thickness is sufficient to provide
adequate protection, and that the 4 inches, as reflected in the RG, is
not intended to be an upper limit on bed thickness. It is acceptable to
provide additional carbon that may include 6 inches, 8 inches, or even
greater bed thickness. The NRC also believes there are benefits
provided by carbon bed thicknesses greater than 4 inches that are not
reflected in the RG. The benefits may include longer bed life
contributing to lower overall cost.
With respect to filtration systems in series, they are treated as a
composite (i.e., the sum of individual filters in series). For example,
the efficiency of two 2-inch beds in series is the same as one 4-inch
bed.
Comment: In response to the petitioner's statement that current TS
for system performance should be eliminated and that the administrative
portion of the TS could include a requirement to have a control room
habitability program, NEI commented, ``This recommendation is covered
by TSTF-448 and GL 2003-01.''
Response: NRC agrees with the comment. NRC prepared and made
available a model safety evaluation (SE) and a model no-significant-
hazards-consideration (NSHC) determination relating to the modification
of technical specification (TS) requirements regarding the habitability
of the control room envelope (CRE) for referencing in license amendment
requests (LARs). NRC also made available an associated model LAR for
use by licensees to prepare such LARs. The TS modification is based on
NRC staff approved changes to the improved standard technical
specifications (STS) (NUREGs 1430-1434, available on NRC's public Web
site at www.nrc.gov/reactors/operating/licensing/techspec/current-approved-sts.html) that were proposed by the pressurized and boiling
water reactor owners groups' Technical Specifications Task Force (TSTF)
on behalf of the commercial nuclear electrical power generation
industry, in STS change traveler TSTF-448, Revision 3 (ML063460558).
NRC published a Notice of Availability of the SER in the Federal
Register on January 17, 2007 (72 FR 2022). Generic Letter (GL) 2003-01,
dated June 12, 2003, is available on ADAMS (ML031620248).
Comment: In response to the petitioner's proposed guidance, NEI
provided the following comments:
The control room ventilation system should isolate on the
detection of high radiation or toxic gas intake. NEI commented, ``A
good many control rooms in the industry already operate in this manner.
Conversely, there are some plants that do not have automatic initiation
of the emergency mode. Making this a requirement could result in an
undue (and expensive) modification/backfit. For those plants
susceptible to toxic gas intrusion, automatic initiation is typically
the case (although not specifically implemented in all cases). If
required, this also could result in undue (and expensive)
modifications.''
The control room should have a minimum of one foot of
concrete shielding (or equivalent) on all surfaces. NEI commented, ``It
is unlikely that all control rooms have one foot of concrete shielding
on all surfaces. This requirement could result in undue (and expensive)
modifications. A similar concern applies to the technical support
center, which may also be affected by this requirement.''
SCBAs and KI tablets should be readily available for
operator use. Operators should maintain training in SCBAs. NEI
commented, ``The use of these methods has merit, but additional
evaluation of their effects is necessary. The medical complications of
ingesting KI would have to be evaluated for all CR personnel. The use
of SCBA credit would require specific training for which operators will
need to demonstrate the ability to conduct their
[[Page 4353]]
safety-related functions while wearing a SCBA for several hours.''
Procedures should be developed to ensure control room
purging is considered when the outside concentration is less than the
inside concentration. NEI commented, ``Although this appears to be a
good practice, it can't be credited in the operator dose analysis. The
timing of purging could be critical based on the timing of the release
and the release pathway. Therefore, this recommendation may not have
any practical merit.''
The petitioner stated that because of the low risk significance of
being outside the control room habitability program guidelines, a plant
shutdown would not be required in this condition; rather, the program
could specify that timely actions should be taken to return the plant
within the guidelines. If not complete within 30 days, a special report
would be sent to the NRC with a justification for continued operation
and a proposed schedule for meeting the guidelines. NEI commented,
``This is a valid point that the industry supports.''
The petitioner stated that as an alternative to total removal of
dose guidelines from the regulations, most of his concerns could be
resolved if the dose criteria were based solely on the whole body dose
from noble gases that he believes is the only possible dose impact that
may result in control room evacuation. NEI commented, ``It is not clear
that the noble gas contribution would be limiting in all cases.
However, this may be the case if KI were allowed to be credited.''
Response: These comments have been addressed in Section III of this
document.
V. Denial of Petition
Based upon review of the petition and comments received, the NRC
has determined that the conclusions upon which the petitioner relies do
not substantiate a basis to eliminate the control room radiological
dose acceptance criteria from current regulations as requested. For the
reasons discussed previously, the Commission denies PRM-50-87.
Dated at Rockville, Maryland, this 14th day of January 2009.
For the Nuclear Regulatory Commission.
Annette L. Vietti-Cook,
Secretary of the Commission.
[FR Doc. E9-1211 Filed 1-23-09; 8:45 am]
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