[Federal Register Volume 64, Number 190 (Friday, October 1, 1999)]
[Proposed Rules]
[Pages 53270-53275]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-25582]


 ========================================================================
 Proposed Rules
                                                 Federal Register
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 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. 64, No. 190 / Friday, October 1, 1999 / 
Proposed Rules  

[[Page 53270]]


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NUCLEAR REGULATORY COMMISSION

10 CFR Part 50

RIN 3150--AG26


Emergency Core Cooling System Evaluation Models

AGENCY: Nuclear Regulatory Commission.

ACTION: Proposed rule.

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SUMMARY: The Nuclear Regulatory Commission (NRC) is proposing to amend 
its regulations to allow holders of operating licenses for nuclear 
power plants to reduce the assumed reactor power level used in 
evaluations of emergency core cooling system (ECCS) performance. Under 
the proposed rule, licensees would be given the option to apply a 
reduced margin for ECCS evaluation or to maintain the value of reactor 
power currently mandated in the regulation. This action would allow 
interested licensees to pursue small, but cost-beneficial, power 
uprates and would reduce unnecessary regulatory burden without 
compromising the margin of safety of the facility.

DATES: The comment period expires on December 15, 1999. Comments 
received after this date will be considered if it is practical to do so 
but the NRC is able to assure consideration only for comments received 
on or before this date.

ADDRESSES: Mail written comments to: Secretary, U.S. Nuclear Regulatory 
Commission, Washington, D.C. 20555-0001, Attention: Rulemakings and 
Adjudications Staff, Mail Stop O-16C1.
    Deliver written comments to: One White Flint North, 11555 Rockville 
Pike, Rockville, Maryland between 7:30 a.m. and 4:15 p.m. on Federal 
workdays.
    Documents related to this rulemaking may be examined at the NRC 
Public Document Room, 2120 L Street, NW. (Lower Level), Washington, 
D.C. Documents also may be viewed and downloaded electronically via the 
interactive rulemaking Web site established by NRC for this rulemaking 
(see the discussion under Electronic Access in the Supplementary 
Information section). Obtain single copies of the environmental 
assessment and the regulatory analysis from the NRC contact given 
below.

FOR FURTHER INFORMATION CONTACT: Mr. Joseph E. Donoghue, Office of 
Nuclear Reactor Regulation, U.S. Nuclear Regulatory Commission, 
Washington, D.C. 20555-0001; telephone: 301-415-1131; or by Internet 
electronic mail to [email protected].

SUPPLEMENTARY INFORMATION:

Background

    A holder of an operating license (i.e., the licensee) for a light-
water power reactor is required by regulations issued by the NRC to 
submit a safety analysis report that contains an evaluation of 
emergency core cooling system (ECCS) performance under loss-of-coolant 
accident (LOCA) conditions. 10 CFR 50.46, ``Acceptance criteria for 
emergency core cooling systems for light-water nuclear power 
reactors,'' requires that ECCS performance under LOCA conditions be 
evaluated and that the estimated performance satisfy certain criteria. 
Licensees may conduct an analysis that ``realistically describes the 
behavior of the reactor system during a LOCA'' (often termed a ``best-
estimate analysis''), or they may develop a model that conforms with 
the requirements of Appendix K to 10 CFR Part 50. Most ECCS evaluations 
are based on Appendix K requirements. The opening sentence of Appendix 
K establishes the requirement to conduct ECCS analyses at a specified 
power level: ``It shall be assumed that the reactor has been operating 
continuously at a power level at least 1.02 times the licensed power 
level (to allow for such uncertainties as instrumentation error).'' 
Licensees have proposed using instrumentation that would reduce the 
uncertainties associated with measurement of reactor power when 
compared with existing methods of power measurement. This would justify 
a reduced margin between the licensed power level and the power level 
assumed for ECCS evaluations. The proposed rule would revise this 
provision in Appendix K, thereby allowing licensees the option of using 
a value lower than 102 percent of licensed power in their ECCS analyses 
where justified.
    Several licensees have expressed interest in using updated 
feedwater flow measurement technology discussed later in ``Calorimetric 
Uncertainty and Feedwater Flow Measurement'' as a basis for seeking 
exemptions from the Appendix K power level requirement and to implement 
power uprates. One licensee, Texas Utilities Electric Company (TUE), 
has obtained an exemption from the Appendix K requirement for Comanche 
Peak Units 1 and 2 and is pursuing an increase in licensed power based, 
in part, on more accurate feedwater flow measurement capability. The 
prospect of additional exemption requests from other licensees provides 
the impetus for the proposed rule.
    The objective of this rulemaking is to reduce an unnecessarily 
burdensome regulatory requirement. Appendix K was issued to ensure an 
adequate performance margin of the ECCS in the event a design-basis 
LOCA were to occur. The margin is provided by conservative features and 
requirements of the evaluation models and by the ECCS performance 
criteria. The existing regulation does not require that the power 
measurement uncertainty be demonstrated, but rather mandates a 2-
percent margin to account for uncertainties, including those expected 
to be involved with measuring reactor power. By allowing licensees to 
justify a smaller margin for power measurement uncertainty, the 
proposed rule does not violate the underlying purpose of Appendix K. 
The intent of Appendix K, to ensure sufficient margin to ECCS 
performance in the event of a LOCA, would still be met because of the 
substantial conservatism of other Appendix K requirements. The proposed 
rule would not significantly affect plant risk, as discussed in the 
section entitled, ``ECCS Evaluation Conservatism.''
    Another objective is to avoid unnecessary exemption requests. As 
discussed above, a licensee has obtained an exemption from the 2-
percent margin requirement in 10 CFR Part 50, Appendix K. It is likely 
that additional exemption requests will be submitted. Revising the rule 
to remove the need for licensees to obtain exemptions is considered by 
the NRC to be a prudent regulatory action.

[[Page 53271]]

    If adopted, the proposed rule would give licensees the option of 
applying a reduced margin between the licensed power level and the 
assumed power level for ECCS evaluation, or maintaining the current 
margin of 2-percent power. As discussed in the section entitled ``ECCS 
Evaluation Conservatism,'' the NRC has concluded that the 2 percent 
power margin requirement in the existing rule appears to be based 
solely on considerations associated with power measurement extant at 
the time of the original ECCS rulemaking. If licensees can show that 
the uncertainties associated with power measurement instrumentation 
errors are less than 2 percent, thereby justifying a smaller margin, 
then the current rule unnecessarily restricts operation.
    Making this change to the rule would give licensees the opportunity 
to use a reduced margin if they determine that there is a sufficient 
benefit. Licensees could apply the margin to gain benefits from 
operation at higher power, or the margin could be used to relax ECCS-
related technical specifications (e.g., pump flows). Another potential 
benefit would be in modifying fuel management strategies (e.g., 
possibly by altering core power peaking factors). However, the proposed 
rule by itself does not allow increases in licensed power levels. 
Because licensed power level for a plant is a technical specification 
limit, proposals to raise the licensed power level must be reviewed and 
approved under the license amendment process. The license amendment 
request should include a justification of the reduced power measurement 
uncertainty and the basis for the modified ECCS analysis, including the 
justification for reduced power measurement uncertainty, should then be 
included in documentation supporting the ECCS analysis (see Section-by-
Section Analysis).
    In the short term, the NRC intends to grant exemptions to the 
assumed power level provision of Appendix K for properly supported 
exemption requests. In addition to satisfying the provisions of 10 CFR 
50.12, properly supported exemption requests are expected to quantify 
the uncertainties associated with measuring reactor thermal power that 
are associated with the current 2-percent power margin.
    In the longer term, the NRC intends to review the affected safety 
analysis guidance and will evaluate the impact of the proposed rule on 
those safety analyses. Further, the NRC is considering the need for 
specific guidance to help licensees appropriately account for power 
measurement uncertainty in safety analyses. However, the NRC expects 
that power uprate amendment requests based on the proposed rule will 
address the suitability of non-LOCA analyses for operation at proposed 
higher power levels.
    In addition to comments on the proposed rule, the NRC is seeking 
comments on the specific issues set forth below under ``Issues for 
Public Comment.''

Conservatisms in Appendix K ECCS Evaluation Model

    Appendix K defines conservative analysis assumptions for ECCS 
performance evaluations during design-basis LOCAs. Large safety margins 
are provided by conservatively selecting the ECCS performance criteria 
as well as conservatively establishing ECCS calculational requirements. 
The major analytical parameters and assumptions that contribute to the 
conservatisms in Appendix K are set forth in Sections A through D of 
the rule: (A) ``Sources of Heat During the LOCA'' (the 102-percent 
power provision is a key factor), (B) ``Swelling and Rupture of the 
Cladding and Fuel Rod Thermal Parameters,'' (C) ``Blowdown Phenomena,'' 
and (D) ``Post-blowdown Phenomena: Heat Removal by ECCS.'' In each of 
these areas, several assumptions are typically used to ensure 
substantial conservatism in the analysis results. For instance: under 
``Sources of Heat During the LOCA,'' decay heat is modeled on the basis 
of an American Nuclear Society standard with an added 20-percent 
penalty, and the power distribution shape and peaking factors expected 
during the operating cycle are chosen to yield the most conservative 
results. In ``Blowdown Phenomena,'' the rule requires use of the Moody 
model and the discharge coefficient that yields the highest peak 
cladding temperature. ``Post'Blowdown Phenomena; Heat Removal by the 
ECCS,'' requires that the analysis assume the most damaging single 
failure of ECCS equipment.
    One of several conservative requirements in Section A is to assume 
that the reactor is operating at 102 percent power when the LOCA occurs 
``to allow for such uncertainties as instrumentation error. . . .'' 
(Appendix K, Section I.A., first sentence, emphasis added). The phrase, 
``such as,'' suggests that the two percent power margin was intended to 
address uncertainties related to heat source considerations beyond 
instrument measurement uncertainties. However, the basis for the 
required assumption of 102 percent power (2 percent power margin) does 
not appear to be contained in the rulemaking record for the ECCS rules, 
10 CFR 50.46 and Appendix K. These rules were adopted in 1974 (39 FR 
1001, January 4, 1974), and were preceded by a formal rulemaking 
hearing which ultimately resulted in a Commission decision on the 
proposed rulemaking, CLI-73-39, 6 AEC 1085 (December 28, 1973). Neither 
the statement of considerations (SOC) for the final rule nor the 
Commission decision appear to provide specific basis for the required 
assumption of 102 percent power.
    The SOC for the final 1974 rule discusses the 102 percent power 
assumption in general terms, and does not mention instrumentation 
uncertainty:

    The Commission believes that the implementation of the new 
regulations will ensure an adequate margin of performance of the 
ECCS should a design basis LOCA ever occur. This margin is provided 
by conservative features of the evaluation models and by the 
criteria themselves. Some of the major points that contribute to the 
conservative nature of the evaluations and the criteria are as 
follows:
    (1) Stored heat. The assumption of 102 percent of maximum power, 
highest allowed peaking factor, and highest estimated thermal 
resistance between the UO2 and the cladding provides a 
calculated stored heat that is possible but unlikely to occur at the 
time of a hypothetical accident. While not necessarily a margin over 
the extreme condition, it represents at least an assumption that an 
accident happens at a time which is not typical.

39 FR at 1002 (first column).1 Thus, while the pre-accident 
power level assumption is connected with the modeling of the rate of 
heat generation after the LOCA occurs, a clear basis for the 102 
percent assumed power level requirement is not provided, nor does the 
SOC explain whether there are other uncertainties besides 
instrumentation uncertainties for which the 102 percent assumed power 
level is intended to compensate.
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    \1\ This statement in the SOC was taken unchanged from Section I 
of the Commission's ECCS decision. See CLI-73-39, 6 AEC 1085, 1093-
94 (December 28, 1973).
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    The Commission's decision in the ECCS rulemaking hearing also does 
not explain whether the 102 percent assumed power level was intended to 
address uncertainties other than instrumentation uncertainties. Section 
I of the Commission decision was the basis for the SOC discussion on 
the 102 percent assumed power level (See 6 AEC at 1093-94). Section 
III. A. of the Commission's decision, ``Required and Acceptable 
Features of the Evaluation Model,'' does not offer a detailed technical 
the basis for the power level chosen, but instead uses the language 
ultimately adopted in the final Appendix K rule:


[[Page 53272]]


    For the heat sources listed in paragraphs 1 to 4 below it shall 
be assumed that the reactor has been operating continuously at a 
power level at least 1.02 times the licensed power level (to allow 
for such uncertainties as instrumentation error), with the maximum 
peaking factor allowed by the technical specifications.

6 AEC at 1100. Thus, the Commission's decision does not shed further 
light on the basis for the 102 percent assumed power level, nor whether 
the Commission had in mind uncertainties other than those associated 
with the instrumentation for measurement of power level.
    NRC review of the ECCS rulemaking hearing record did not disclose 
presentations relating to quantification of power measurement 
uncertainties, or the magnitude of other uncertainties that the 102 
percent assumed power level may have been intended to address. The 
Commission decision (CLI-73-39, 6 AEC 1085, December 28, 1973) cited 
three documents in the rulemaking hearing record. The first, cited in 
the Commission decision as Exhibit 1113, was ``Supplemental Testimony 
of the AEC Regulatory Staff on the Interim Acceptance Criteria for 
Emergency Core Cooling Systems for Light-Water Cooled Power Reactors,'' 
(filed October 26, 1972). In Section 10 of the document, stored energy 
in the fuel was considered, specifically the expected power 
distributions in fuel rods. The 102-percent power analysis requirement 
is not discussed. The second item, cited in the Commission decision as 
Exhibit 1137 was ``Redirect and Rebuttal Testimony of Dr. Donald H. Roy 
on Behalf of Babcock & Wilcox,'' (October 26, 1972) in which the 
characteristic of the decay heat release following reactor shutdown was 
discussed. In this document, the 102-percent assumption is associated 
with the predicted decay heat generation rate. The over-power condition 
is associated with a ``design-basis maneuvering operation,'' but the 
basis for the value of power chosen for the analysis (i.e., 102 
percent) is not disclosed. Finally, in the ``Concluding Statement of 
Position of the Regulatory Staff--Public Rulemaking Hearing on: 
Acceptance Criteria for Emergency Core Cooling Systems for Light-Water 
Cooled Nuclear Power Reactors,'' April 16, 1973 (the Concluding 
Statement), the power level assumption is included as part of the 
proposed rule itself. The proposed rule language clearly states that 
the power level assumption is to ``allow for instrumentation error.'' 
The term ``such as'' does not appear here. It is unclear when or why 
the proposed language in this regard was changed to its current form. 
The power level assumption is mentioned again in the Concluding 
Statement indirectly in association with power level changes before the 
LOCA and the effect on decay heat generation. But it is discussed most 
directly with regard to initial stored energy in the fuel. In the 
discussion on stored energy, the 102-percent assumption is attributed 
to ``uncertainties inherent in the measurement of the operating power 
level of the core,'' (page 144 of the Concluding Statement). Reasons 
for choosing 102-percent as the value are not discussed.
    When Appendix K was first issued, as is the case today, the thermal 
power generated by a nuclear power plant was determined by steam plant 
calorimetry, which is the process of performing a heat balance around 
the nuclear steam supply system (called a calorimetric). The heat 
balance depends upon measurement of several plant parameters, including 
flow rates and fluid temperatures. The differential pressure across a 
venturi installed in the feedwater flow path is a key element in the 
calorimetric measurement. Licensees have proposed using instrumentation 
other than a venturi-based system to obtain feedwater flow rate for 
calorimetrics. The lower uncertainty associated with the new 
instrumentation is information that was apparently not available during 
the original Appendix K rulemaking.
    In view of the regulatory history for Appendix K, the Commission 
now believes that the 2-percent margin embodied in the requirement for 
a 102-percent assumed power level in Appendix K was based solely on 
uncertainties associated with the measurement of reactor power level.

Proposed Reduction in 102 Percent Assumed Power Level

    The Commission believes that other requirements of Appendix K 
modeling include substantial conservatisms of much greater magnitude 
than the 2 percent margin embodied in the requirement for a 102 percent 
assumed power level. This point was discussed in ``Conservatisms in 
Appendix K ECCS Evaluation Model,'' above.
    The Commission is also aware of new information gained since the 
1974 rulemaking which shows that the Appendix K model contains 
substantial conservatisms. Evidence from experiments designed to 
simulate LOCA phenomena suggest that these conservatisms added hundreds 
of degrees Fahrenheit to the prediction of peak fuel cladding 
temperature than would actually occur during a LOCA. The significant 
conservatism was necessary when the rule was written because of a lack 
of experimental evidence at that time with respect to the relative 
effects of analysis input parameters, including pre-accident power 
level. Since that time, there has been substantial additional research 
on LOCA. NUREG-1230, ``Compendium of ECCS Research for Realistic LOCA 
Analysis,'' December 1988, contains the technical basis for improved 
understanding of LOCA progression and ECCS evaluation gained after the 
ECCS rule was issued. The NUREG includes a discussion of the basis for 
uncertainties in detailed fuel bundle power calculations as part of the 
consideration of overall calculational uncertainty inherent in best-
estimate evaluations. Chapters 7 and 8 of the NUREG include 
consideration of the changes in licensed power level that could result 
from application of best-estimate evaluation methods. The discussion 
includes an estimated sensitivity of predicted peak clad temperature 
associated with changes in pre-accident power level. From that 
estimate, the NRC expects peak cladding temperature changes of 
approximately 15 deg.F to result from 1-percent changes in plant power 
level that could result from the proposed rule.
    In view of: (i) Substantial conservatisms embodied in the Appendix 
K requirements for ECCS evaluations, (ii) new information developed 
since the 1974 rulemaking which shows additional conservatism in the 
Appendix K modeling requirements beyond that understood by the 
Commission when it adopted the 1974 rule, and (iii) the relative 
insensitivity of the calculated clad temperatures to assumed power 
level, the Commission concludes that it is acceptable to allow a 
reduction in the currently-required 102 percent power level assumption 
if justified by the actual power level measurement instrumentation 
uncertainty. Accordingly, the Commission proposes to amend the Appendix 
K requirement for an assumed 102 percent power level. The proposed rule 
would allow a licensee to use an assumed power level of less than 102 
percent (but not less than 100 percent), provided that the licensee has 
determined that the uncertainties in the measurement of core power 
level justifies the reduced margin.

Calorimetric Uncertainty and Feedwater Flow Measurement

    The NRC staff has approved an exemption to the 102-percent power 
level requirement for Comanche Peak Units 1 and 2. The basis for the 
action is application of upgraded feedwater flow measurement technology 
at the

[[Page 53273]]

plant. As indicated, the prospect of additional licensees requesting 
similar action has prompted the proposed rule. Other methods, systems, 
or analyses could be used as the basis for demonstrating reduced power 
measurement uncertainty.
    In most nuclear power plants, operators obtain a continuous 
indication of core thermal power from nuclear instruments, that provide 
a measurement of neutron flux. The nuclear instruments must be 
periodically calibrated to counteract the effects of changes in flux 
pattern, fuel burnup, and instrument drift. Steam plant calorimetry, 
which is the process of performing a heat balance around the nuclear 
steam supply system (called a calorimetric), is used to determine core 
thermal power and is the basis for the calibration. The differential 
pressure across a venturi installed in the feedwater flow path is a key 
element in the calorimetric measurement. Some plants use this 
calorimetric value directly to indicate thermal power; the nuclear 
instruments are used as anticipatory indicators for transients and for 
reactivity adjustments made with the control rods.
    The system in use at Comanche Peak Units 1 and 2 is the Leading 
Edge Flowmeter (LEFM), manufactured by Caldon, Inc. The LEFM system is 
an ultrasonic flow meter that measures the transit times of pulses 
traveling along parallel acoustic paths through the flowing fluid. LEFM 
technology has been employed in non-nuclear applications, such as 
petroleum, chemical, and hydroelectric plants for several years. This 
operating experience will provide reliability data, supplementing data 
from nuclear applications. Additional information on the Comanche Peak 
Appendix K exemption and on the Caldon, Inc. LEFM system appears in 
safety evaluations issued by the NRC staff on March 8, 1999, and May 6, 
1999.
    ABB Combustion Engineering has expressed interest in the proposed 
rule because its flow-measuring system, known as Crossflow (which is 
also an ultrasonic flow-measuring device), is expected to be part of a 
licensee exemption request in the near future.

Issues for Public Comment

    The NRC is seeking comments from the public on the following issues 
related to this proposed rule:
    1. The current rule states that the required 2-percent analysis 
margin is to account for ``such uncertainties as instrumentation error. 
. . .'' (emphasis added). This suggests that the 2-percent margin was 
intended to account for other sources of uncertainty in addition to 
instrumentation error. However, explicit documentation of the basis for 
the value of the margin does not appear to be contained in the 
rulemaking record for the original 1974 ECCS rulemaking. The Commission 
is interested in whether there are other sources of uncertainty, 
relevant to sources of heat following a LOCA, that should be considered 
when licensees seek to reduce the margin in the Appendix K requirement 
for assumed power. If other contributors are suggested, a clear 
technical justification should accompany the suggestion.
    2. Are there rulemaking alternatives to this proposed rule that 
were not considered in the regulatory analysis for this proposed rule?
    3. What criteria should be used for determining whether a proposed 
reduction in the 2 percent power margin has been justified, based upon 
a determination of instrumentation error? For example, should a 
demonstrated instrumentation error of 1 percent in power level be 
presumptive of an acceptable reduction in assumed power margin of 1 
percent?
    4. How should the proposed rule address cases in which licensees 
determine that power measurement instrument error is greater than 2 
percent?

Section-by-Section Analysis

Appendix K to Part 50--ECCS Evaluation Models (I)(A)--Sources of heat 
during the LOCA

    This section would be amended by removing words from the first 
sentence in the section to specifically associate the power level 
requirement with instrumentation error, and by adding a sentence 
immediately following the first sentence in the section. The new 
sentence indicates that licensees may assume a power level lower than 
102 percent, but not less than 100 percent, provided that the proposed 
lower alternative value can be shown to account for core thermal power 
measurement instrumentation uncertainty.
    Appendix K, Part II (1)(a) requires that the values of analysis 
parameters or their basis be sufficiently documented to allow NRC 
review. The requirement applies to all analysis input parameters, 
including those related to other plant instrumentation, such as 
temperature and pressure. Changes to other inputs are documented in the 
same manner as the power measurement uncertainty would be documented 
under the proposed rule. NRC review and approval is not necessarily 
needed to change a parameter in an approved ECCS evaluation model. 
Estimated changes in ECCS performance due to revised analysis inputs 
are reported under Sec. 50.46 (a)(3), at least annually. As discussed 
in the Statement of Considerations for Appendix K (53 FR 36001, 
September 16, 1988), the annual reports keep NRC apprised of changes. 
This should ensure that the NRC staff can judge a licensee's assessment 
of the significance of changes and maintain cognizance of modifications 
made to NRC-approved evaluation models. The licensee must include 
revised parameters and other changes in the ECCS evaluation as required 
by Sec. 50.46 (a)(3) when a single change or an accumulation of changes 
is expected to affect peak cladding temperature by 50 deg.F or more. 
The basis for the revised analysis parameter (i.e., the assumed power 
level) should be included in documentation of the evaluation model, as 
required by Appendix K, Part II (1)(a).
    In most cases, the NRC expects that the analysis supporting the 
power measurement uncertainty, as well as the description of the 
relevant instrumentation and associated plant-specific parameters 
involved in the uncertainty analysis, would be submitted for NRC review 
and approval before being used. These requests are expected because 
most licensees have adopted Generic Letter 88-16, ``Removal of Cycle-
Specific Parameter Limits from Technical Specifications.'' The generic 
letter provided guidance for licensees to transfer cycle-specific 
parameters from their technical specifications to a Core Operating 
Limits Report (COLR). Licensees following the generic letter guidance 
added an administrative requirement to their technical specifications 
that specifically identifies NRC-reviewed and approved methods used to 
determine core operating limits (e.g., topical reports). Because a 
number of core operating limits are based on LOCA analysis results, 
ECCS evaluation methods are included in the technical specification 
list. Therefore, most licensees opting to use the relaxation in the 
proposed rule would need to revise technical specifications to include 
a reference to an NRC-approved topical report that includes the 
uncertainty analysis justifying reduced power measurement uncertainty.
    An additional technical specification consideration for licensees 
pursuing changes based on the proposed rule could involve nuclear 
instruments (NI) requirements. Existing plant technical specifications 
include surveillance requirements to calibrate the power range NIs 
based on the calorimetric measuring reactor thermal power. The

[[Page 53274]]

NIs provide the indication of reactor power used as an input for safety 
systems. Licensees obtaining the relaxation offered in the proposed 
rule are expected to change some operating parameter of the plant, 
whether it be power level, required ECCS flow, etc. By incorporating 
the justification of reduced uncertainty in power measurement in the 
basis for their ECCS analysis, licensees would be placing a condition 
on an input to the calorimetric. The NI calibration required by the 
plant licensee would then be based on a calorimetric assuming the 
reduced power measurement uncertainty. If, for some reason, during the 
course of plant operation the reduced uncertainty did not apply (e.g., 
the new feedwater flow meter became inoperable), the calorimetric would 
no longer be a valid source of calibration for the NIs. Licensees would 
need to take action to maintain compliance with their technical 
specification, for example, by using an alternate input to the 
calorimetric. The power measurement uncertainties associated with the 
alternate input would then apply and the plant would need to adjust its 
operating condition (possibly lower its operating power level) to 
satisfy the proposed rule and to maintain the validity of applicable 
safety analyses.

Referenced Documents

    Copies of GL-88-16 and CLI-73-39 are available for inspection and 
copying for a fee at the NRC Public Document Room, 2120 L Street, NW. 
(Lower Level), Washington, D.C.

Electronic Access

    You may also submit comments via the NRC's interactive rulemaking 
Web site, ``Rulemaking Forum,'' through the NRC home page (http://
ruleforum.llnl.gov). This site enables people to transmit comments as 
files (in any format, but WordPerfect version 6.1 is preferred), if 
your Web browser supports that function. Information on the use of the 
Rulemaking Forum is available on the Web site. For additional 
assistance on the use of the interactive rulemaking site, contact Ms. 
Carol Gallagher, telephone: 301-415-5905; or by Internet electronic 
mail to [email protected].

Plain Language

    The Presidential memorandum dated June 1, 1998, entitled, ``Plain 
Language in Government Writing,'' directed that the government's 
writing be in plain language. This memorandum was published June 10, 
1998 (63 FR 31883). In complying with this directive, editorial changes 
have been made in this proposed amendment to improve readability of the 
existing language of the provisions being revised. These types of 
changes are not discussed further in this document. The NRC requests 
comment on the proposed rule specifically with respect to the clarity 
and effectiveness of the language used. Comments should be sent to the 
address listed under the ADDRESSES caption of the preamble.

Voluntary Consensus Standards

    The National Technology Transfer Act of 1995, Pub. L. 104-113, 
requires that Federal agencies use technical standards that are 
developed or adopted by voluntary consensus standards bodies unless the 
use of such a standard is inconsistent with applicable law or otherwise 
impractical. In this proposed rule, the NRC is proposing to provide 
holders of operating licenses for nuclear power plants with the option 
of reducing the assumed reactor power level used in ECCS evaluations. 
This proposed action constitutes a modification to an existing 
government-unique standard, 10 CFR part 50, appendix K issued by the 
NRC on January 4, 1974. The NRC is not aware of any voluntary consensus 
standard that could be adopted instead of the proposed government-
unique standard. The NRC will consider using a voluntary consensus 
standard if an appropriate standard is identified. If a voluntary 
consensus standard is identified for consideration, the submittal must 
explain how the voluntary consensus standard is comparable and why it 
should be used instead of the proposed government-unique standard.

Finding of No Significant Environmental Impact: Availability

    The NRC has determined under the National Environmental Policy Act 
of 1969, as amended, and the NRC's regulations in Subpart A of 10 CFR 
Part 51, that this regulation, if adopted, would not be a major Federal 
action significantly affecting the quality of the human environment 
and, therefore, an environmental impact statement is not required.
    The proposed action is likely to result in relatively small changes 
to ECCS analyses or to the licensed power of nuclear reactor 
facilities. The NRC staff expects that no significant environmental 
impact would result from the proposed rule, because licensee actions 
based on the proposed rule would not significantly increase the 
probability or consequences of accidents; no changes would be made in 
the types of any effluents that may be released off site; and there 
would be no significant increase in occupational or public radiation 
exposure. Therefore, there are no significant radiological 
environmental impacts associated with the proposed action. The proposed 
action does not involve non-radiological plant effluents and has no 
other environmental impact. Therefore, there are no significant non-
radiological environmental impacts associated with the proposed action.
    The determination of the environmental assessment is that there 
would be no significant offsite impact on the public from this action. 
However, the general public should note that the NRC welcomes public 
participation. Also, the NRC has committed itself to complying in all 
its actions with Executive Order (E.O.) 12898, ``Federal Actions To 
Address Environmental Justice in Minority Populations and Low-Income 
Populations,'' dated February 11, 1994. The NRC has determined that 
there are no disproportionately high and adverse impacts on minority 
and low-income populations. In the letter and spirit of E.O. 12898, the 
NRC is requesting public comments on any environmental justice 
considerations or questions that the public thinks may be related to 
this proposed rule, but that somehow were not addressed. The NRC uses 
the following working definition of environmental justice: 
Environmental justice means the fair treatment and meaningful 
involvement of all people, regardless of race, ethnicity, culture, 
income, or educational level with respect to the development, 
implementation and enforcement of environmental laws, regulations, and 
policies. Comments on any aspect of the environmental assessment, 
including environmental justice, may be submitted to the NRC as 
indicated under the ADDRESSES heading.
    The draft environmental assessment is available for inspection at 
the NRC Public Document Room, 2120 L Street NW. (Lower Level), 
Washington, D.C. Single copies of the environmental assessment are 
available from Mr. Joseph Donoghue, Office of Nuclear Reactor 
Regulation, U.S. Nuclear Regulatory Commission, Washington, D.C. 20555-
0001, telephone: 301-415-1131, or by Internet electronic mail to 
JED[email protected].

Paperwork Reduction Act Statement

    This proposed rule increases the burden on licensees opting to use 
a reduced power level assumption for ECCS analysis (i.e., below 102%) 
to include the change in their annual

[[Page 53275]]

report required under 10 CFR 50.46 (a)(3)(ii). The public burden for 
this information collection is estimated to average one-half hour per 
response. Because the burden for this information collection is 
insignificant, Office of Management and Budget (OMB) clearance is not 
required. Existing requirements were approved by the Office of 
Management and Budget, approval number 3150-0011.

Public Protection Notification

    If a means used to impose an information collection does not 
display a currently valid OMB control number, the NRC may not conduct 
or sponsor, and a person is not required to respond to, the information 
collection.

Regulatory Analysis

    The Commission has prepared a regulatory analysis on this 
regulation. Interested persons may examine a copy of the regulatory 
analysis at the NRC Public Document Room, 2120 L Street NW. (Lower 
Level), Washington, D.C. Single copies of the analysis are available 
from Mr. Joseph Donoghue, Office of Nuclear Reactor Regulation, U.S. 
Nuclear Regulatory Commission, Washington, D.C. 20555-0001, telephone: 
301-415-1131, or by Internet electronic mail to [email protected].

Regulatory Flexibility Certification

    As required by the Regulatory Flexibility Act of 1980, 5 U.S.C. 
605(b), the Commission certifies that this proposed rule, if adopted, 
would not have a significant economic impact on a substantial number of 
small entities. This proposed rule would affect only the licensing and 
operation of nuclear power plants. The companies that own these plants 
do not fall within the definition of ``small entities'' found in the 
Regulatory Flexibility Act or within the size standards established by 
the NRC in 10 CFR 2.810.

Backfit Analysis

    The NRC has determined that the backfit rule in 10 CFR 50.109 does 
not apply to this proposed rule and that a backfit analysis is not 
required for this proposed rule because the change does not involve any 
provisions that would impose backfits as defined in 10 CFR 
50.109(a)(1). The proposed rule would establish an alternative approach 
for ECCS performance evaluations that may be voluntarily adopted by 
licensees. Licensees may continue to comply with existing requirements 
in Appendix K. The proposed rule does not impose a new requirement on 
current licensees and therefore, does not constitute a backfit as 
defined in 10 CFR 50.109(a)(1).

List of Subjects in 10 CFR Part 50

    Antitrust, Classified information, Criminal penalties, Fire 
protection, Intergovernmental relations, Nuclear power plants and 
peactors, Radiation protection, Reactor siting criteria, Reporting and 
recordkeeping requirements.

    Accordingly, we propose to amend 10 CFR part 50 as follows:

PART 50--DOMESTIC LICENSING OF PRODUCTION AND UTILIZATION 
FACILITIES

    1. The authority citation for Part 50 continues to read as follows:

    Authority: Sections 102, 103, 104, 105, 161, 182, 183, 186, 189, 
68 Stat. 936, 937, 938, 948, 953, 954, 955, 956, as amended, sec. 
234, 83 Stat. 444, as amended (42 U.S.C. 2132, 2133, 2134, 2135, 
2201, 2232, 2233, 2236, 2239, 2282); secs. 201, as amended, 202, 
206, 88 Stat. 1242, as amended, 1244, 1246 (42 U.S.C. 5841, 5842, 
5846).
    Section 50.7 also issued under Pub. L. 95-601, sec. 10, 92 Stat. 
2951 (42 U.S.C. 5851). Section 50.10 also issued under secs. 101, 
185, 68 Stat. 955, as amended (42 U.S.C. 2131, 2235), sec. 102, Pub. 
L. 91-190, 83 Stat. 853 (42 U.S.C. 4332). Sections 50.13, 50.54(dd), 
and 50.103 also issued under sec. 108, 68 Stat. 939, as amended (42 
U.S.C. 2138). Sections 50.23, 50.35, 50.55, and 50.56 also issued 
under sec. 185, 68 Stat. 955 (42 U.S.C. 2235). Sections 50.33a, 
50.55a, and Appendix Q also issued under sec. 102, Pub. L. 91-190, 
83 Stat. 853 (42 U.S.C. 4332). Sections 50.34 and 50.54 also issued 
under sec. 204, 88 Stat. 1245 (42 U.S.C. 5844). Sections 50.58, 
50.91, and 50.92 also issued under Pub. L. 97-415, 96 Stat. 2073 (42 
U.S.C. 2239). Section 50.78 also issued under sec. 122, 68 Stat. 939 
(42 U.S.C. 2152). Sections 50.80-50.81 also issued under sec. 184, 
68 Stat. 954, as amended (42 U.S.C. 2234). Appendix F also issued 
under sec. 187, 68 Stat. 955 (42 U.S.C. 2237).

    2. Appendix K to Part 50 is amended by revising the introductory 
paragraph of I. A., ``Sources of heat during the LOCA,'' to read as 
follows.

Appendix K to Part 50--ECCS Evaluation Models

I. Required and Acceptable Features of the Evaluation Models

    A. Sources of heat during the LOCA. For the heat sources listed 
in paragraphs I. A. 1 to 4 of this appendix it must be assumed that 
the reactor has been operating continuously at a power level at 
least 1.02 times the licensed power level (to allow for 
instrumentation error), with the maximum peaking factor allowed by 
the technical specifications. An assumed power level lower than the 
level specified in this paragraph (but not less than the licensed 
power level) may be used provided the proposed alternative value has 
been demonstrated to account for uncertainties due to power level 
instrumentation error. A range of power distribution shapes and 
peaking factors representing power distributions that may occur over 
the core lifetime must be studied. The selected combination of power 
distribution shape and peaking factor should be the one that results 
in the most severe calculated consequences for the spectrum of 
postulated breaks and single failures that are analyzed.
* * * * *
    Dated at Rockville, Maryland, this 27th day of September, 1999.

    For the Nuclear Regulatory Commission.
Kenneth R. Hart,
Acting, Secretary of the Commission.
[FR Doc. 99-25582 Filed 9-30-99; 8:45 am]
BILLING CODE 7590-01-P