[Federal Register Volume 68, Number 233 (Thursday, December 4, 2003)]
[Proposed Rules]
[Pages 67811-67812]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-30148]


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 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. 68, No. 233 / Thursday, December 4, 2003 / 
Proposed Rules  

[[Page 67811]]



NUCLEAR REGULATORY COMMISSION

10 CFR Part 50

[Docket No. PRM-50-74]


Nuclear Energy Institute; Denial of Petition for Rulemaking

AGENCY: Nuclear Regulatory Commission.

ACTION: Petition for rulemaking: denial.

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SUMMARY: The Nuclear Regulatory Commission (NRC) is denying a petition 
for rulemaking (PRM-50-74) submitted by the Nuclear Energy Institute 
(NEI or petitioner). The petitioner requested that the NRC amend its 
regulations regarding emergency core cooling systems to allow licensees 
the optional use of the 1994 American Nuclear Society (ANS) decay heat 
standard and to allow the use of any future NRC-approved revisions of 
the standard without additional rulemaking. The NRC is denying the 
petition primarily because an option to use best-estimate evaluation 
models is already available to its licensees, which would allow 
additional operational flexibility. Also, the requested rulemaking 
would reduce conservatism in an individual portion of NRC regulations 
without consideration of other potential overall non-conservatism 
within that portion of the regulations.

ADDRESSES: Publicly available documents related to this petition for 
rulemaking may be viewed electronically on the public computers located 
at the NRC's Public Document Room (PDR), O1 F21, One White Flint North, 
11555 Rockville Pike, Rockville, Maryland. Documents may be copied by 
the PDR reproduction contractor for a fee.
    These documents are also available electronically at NRC's 
Electronic Reading Room on the Internet at http://www.nrc.gov/reading-rm/adams.html. From this site, the public can gain entry into the NRC's 
Agencywide Document Access and Management System (ADAMS), which 
provides text and image files of NRC's public documents. For further 
information contact the PDR reference staff at 1-(800) 387-4209 or 
(301) 415-4737 or by e-mail to [email protected].
    Selected documents, including comments, may be viewed and 
downloaded electronically via the NRC rulemaking web site at http://ruleforum.llnl.gov.

FOR FURTHER INFORMATION CONTACT: Peter C. Wen, Office of Nuclear 
Reactor Regulation, U.S. Nuclear Regulatory Commission, Washington, DC 
20555-0001, telephone (301) 415-2832, e-mail [email protected].

SUPPLEMENTARY INFORMATION:

Background

    Section 50.46 specifies the performance criteria against which the 
emergency core cooling system (ECCS) must be evaluated. The criteria 
include the maximum peak cladding temperature, the maximum cladding 
oxidation thickness, the maximum total hydrogen generation, and 
requirements to assure a coolable core geometry and abundant long-term 
cooling. This regulation also states that the calculated ECCS cooling 
performance following postulated loss-of-coolant accidents (LOCAs) must 
be calculated in accordance with either a realistic (also called best-
estimate) evaluation model that accounts for uncertainty or an 
evaluation model that conforms with the required conservative features 
of Appendix K evaluation models. The use of the 1971 ANS standard on 
decay heat calculation is one of the features required in the Appendix 
K ECCS evaluation models.

The Petition

    On September 6, 2001, the Nuclear Energy Institute (NEI) submitted 
a petition for rulemaking (PRM), designated PRM-50-74. NEI proposed a 
rulemaking to amend Appendix K to 10 CFR part 50 to allow licensees the 
optional use of the 1994 ANS decay heat standard and to allow the use 
of any future NRC-approved revisions of the standard without additional 
rulemaking.
    In PRM-50-74, the petitioner stated that the 1994 ANS decay heat 
standard incorporates more precise results and uses a statistical 
approach to address uncertainty. The petitioner proposed a rulemaking 
to amend Appendix K to 10 CFR part 50 to allow licensees the optional 
use of this most current consensus decay heat standard. The petitioner 
indicated that the amendment would (1) allow licensees to gain 
operating margin for ECCS equipment based on the more realistic decay 
heat assumptions in the 1994 ANS standard; (2) result in more effective 
utilization of resources in operating and maintaining the ECCS 
equipment; and (3) result in the potential for higher extended power 
uprates.

Public Comments on the Petition

    The notice of receipt of the petition and request for public 
comment was published in the Federal Register (FR) on October 11, 2001 
(66 FR 51884). The public comment period ended on December 26, 2001. 
Five letters of public comment were received in response to PRM-50-74. 
Four letters from industry (the Progress Energy Company, the Tennessee 
Valley Authority, Strategic Teaming and Resource Sharing, and the 
Nuclear Management Company) were in favor of the proposal, and one 
letter from an individual (Mr. Bob Leyse) was opposed. Mr. Leyse stated 
that ``the entire body of ECCS evaluation models should be reviewed by 
the NRC rather than a piecemeal approach of selecting only those 
aspects that may be unduly restrictive.''

Reasons for Denial

    The NRC is denying PRM-50-74 primarily because Sec.  50.46 already 
includes provisions for the use of best-estimate evaluation models by 
NRC licensees. In addition, the request would reduce conservatism in an 
individual portion of NRC regulations without consideration of other 
potential overall non-conservatism within that portion of the 
regulations.
    The provisions of Sec.  50.46 allow licensees use of ``best-
estimate'' evaluation models to perform analysis of ECCS cooling 
performance during LOCAs. This approach provides licensees with a more 
accurate determination of their plants' response to a LOCA, while 
allowing additional operational flexibility. The best-estimate 
evaluation represents improved and modern techniques in analyzing LOCA 
behavior. Thus, the NRC prefers the use of best-estimate models, rather 
than the piecemeal approach to updating the Appendix K evaluation 
models.

[[Page 67812]]

    A concomitant factor that influenced the NRC's position is the 
NRC's awareness of a number of phenomena that are known to contribute 
non-conservatism to the Appendix K evaluation models. These phenomena 
include boiling in the downcomer annulus during reflood, downcomer 
entrainment and inventory reduction due to steam bypass, and fuel 
relocation following cladding swelling during the temperature 
transient. The NRC believes that if changes are made in the decay heat 
standard, then changes would also have to be considered in other models 
to ensure that an appropriate level of overall conservatism is retained 
in the ECCS evaluation model package.
    In addition, the NRC has evaluated the advantages and disadvantages 
of the rulemaking requested by the petitioner with respect to the four 
NRC Strategic Performance Goals as follows:
    1. Maintaining Safety: The NRC believes that the requested 
rulemaking would not make a significant contribution to maintaining 
safety because the overall conservatism provided by the Appendix K 
evaluation models may not be appropriately accounted for if the 
conservatism of using the 1971 ANS decay heat standard is individually 
removed.
    2. Enhancing Public Confidence: The proposed rulemaking would not 
enhance public confidence without an overall assessment of ECCS 
evaluation model conservatism. The NRC believes that if changes are 
made in the decay heat standard, then changes would also have to be 
considered in other models to ensure that an appropriate level of 
overall conservatism is retained in the ECCS evaluation model package.
    3. Improving Efficiency and Effectiveness: The NRC staff believes 
that it would not be efficient and effective to modify the Appendix K 
evaluation model using a piecemeal approach when the ``best-estimate'' 
evaluation model is already available for licensees use.
    4. Reducing Unnecessary Regulatory Burden: The NRC agrees that the 
proposed rule would reduce licensees' regulatory burden. However, the 
NRC does not agree that the associated burden is ``unnecessary'' in the 
absence of a demonstration that overall conservatism retained in the 
Appendix K evaluation models would remain adequate. For reasons cited 
in this document, the NRC denies the petition.

    Dated at Rockville, Maryland, this 26th day of November, 2003.

    For the Nuclear Regulatory Commission.
J. Samuel Walker,
Acting Secretary of the Commission.
[FR Doc. 03-30148 Filed 12-3-03; 8:45 am]
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