[Federal Register Volume 76, Number 10 (Friday, January 14, 2011)]
[Notices]
[Pages 2726-2727]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2011-723]


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NUCLEAR REGULATORY COMMISSION

[NRC-2011-0010]


Withdrawal of Regulatory Guide 1.154

AGENCY: Nuclear Regulatory Commission.

ACTION: Withdrawal of Regulatory Guide 1.154, ``Format and Content of 
Plant-Specific Pressurized Thermal Shock Safety Analysis Reports for 
Pressurized Water Reactors.''

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FOR FURTHER INFORMATION CONTACT: Mekonen M. Bayssie, Regulatory Guide 
Development Branch, Division of Engineering, Office of Nuclear 
Regulatory Research, U.S. Nuclear Regulatory Commission, Washington, DC 
20555-0001, telephone: 301-251-7489 or e-mail: <a href="/cdn-cgi/l/email-protection#b3fed6d8dcddd6dd9df1d2cac0c0dad6f3ddc1d09dd4dcc5"><span class="__cf_email__" data-cfemail="1c51797773727972325e7d656f6f75795c726e7f327b736a">[email protected]</span></a>.

SUPPLEMENTARY INFORMATION:

I. Introduction

    The U.S. Nuclear Regulatory Commission (NRC) is withdrawing 
Regulatory Guide (RG) 1.154, ``Format and Content of Plant-Specific 
Pressurized Thermal Shock Safety Analysis Reports for Pressurized Water 
Reactors.'' RG 1.154 was issued by NRC in January 1987 to describe the 
format and content acceptable to the NRC staff for plant-specific 
pressurized thermal shock (PTS) safety analyses, and to describe 
acceptance criteria that NRC staff will use in evaluating licensee 
analyses and proposed corrective measures.
    In recent years, the NRC's Office of Nuclear Regulatory Research 
(RES) developed a technical basis that supported updating the PTS 
regulations in Title 10, Section 50.61, of the Code of Federal 
Regulations (10 CFR 50.61). This technical basis, as described in 
NUREG-1806 and in NUREG-1874, concluded that the risk of through-wall 
pressure vessel cracking due to a PTS event is much lower than 
previously estimated. This finding indicated that the reference 
temperature (RT) screening criteria in 10 CFR 50.61 are overly 
conservative and may impose an unnecessary burden on some licensees. 
Therefore, the NRC developed a new rule, 10 CFR 50.61a, ``Alternate 
Fracture Requirements for Protection against Pressurized Thermal Shock 
Events'' (SECY-09-0059: ``Final Rule Related to Alternate Fracture 
Toughness Requirements for Protection Against Pressurized Thermal Shock 
Events,'' RIN 3150-AI01, April 9, 2009). The alternative rule allows, 
but does not require, that licensees may comply with more permissive RT 
limits that were derived in a risk-informed manner provided that 
certain requirements regarding vessel inspection and surveillance 
programs, as outlined in 10 CFR 50.61a, are met.
    In the course of developing 10 CFR 50.61a, it became clear to staff 
that the guidance provided by RG 1.154 is significantly outdated and, 
in some cases, technically deficient. As such, a plant-specific PTS 
analysis performed based on guidance in RG 1.154 will not be acceptable 
to the staff. While the methods and procedures were appropriate based 
on the situation in the industry when RG 1.154 was developed (1987), 
the methods and procedures have since either passed into common 
practice among plant operators, or were accounted for in the 
development of 10 CFR 50.61a. A fundamental premise underlying RG 1.154 
is that the RT screening criteria in 10 CFR 50.61 are based on a large 
number of conservative assumptions. As such, RG 1.154 postulates that 
it is possible to perform a plant-specific analysis to show that some 
conservatism could reasonably be removed while still demonstrating that 
a plant can be operated at an acceptably low level of risk. The 
technical basis for 10 CFR 50.61a, however, considered the most 
accurate models and input values presently available given the current 
state of the science. This had the effect of eliminating much of the 
conservatism that was embedded in the more restrictive 10 CFR 50.61 RT 
screening criteria. This calls into question whether a strong case 
could be made to remove further conservatism in a plant-specific PTS 
analysis performed in accordance with RG 1.154. Moreover, RG 1.154 
frequently discusses the ``licensee's proposed program of corrective 
measures,'' reflecting the view that there are actions that an 
individual licensee can take, beyond present practices, that will 
mitigate the PTS risk. The continued validity of this premise is also 
questionable. An assessment of

[[Page 2727]]

potential corrective measures described in RG 1.154 indicates that they 
are either impractical or that they have already been implemented 
because of changes to standard industry practices since the issuance of 
the RG in 1987. RG 1.154 lists five general classes of potential 
corrective actions. The current assessment suggests that few of the 
corrective actions listed in RG 1.154 would effectively mitigate PTS 
risk relative to the baseline risk established by the technical basis 
documents that support the alternative rule 10 CFR 50.61a. Licensees 
have a choice to apply more conservative screening criteria in 10 CFR 
50.61 or more permissive and risk-informed criteria in the alternative 
rule 10 CFR 50.61a. If a licensee chooses to apply the screening 
criteria in 10 CFR 50.61 to their plant, and the plant is projected to 
reach the screening limits in 10 CFR 50.61, the licensee can either 
choose to follow procedures prescribed in 10 CFR 50.61 (b)(3) on 
implementing flux reduction measures or 10 CFR 50.61 (b)(4) on 
performing plant-specific safety analysis. However, if a licensee 
chooses to follow 10 CFR 50.61 (b)(4) on performing safety analysis, 
Regulatory Guide 1.154 cannot be used, as it is hereby being withdrawn.

II. Further Information

    The withdrawal of RG 1.154 does not alter any prior or existing 
licensing commitments based on its use. Regulatory guides may be 
withdrawn when their guidance no longer provides useful information, or 
is superseded by technological, congressional action, or other events.
    Guides are revised for a variety of reasons, and the withdrawal of 
a regulatory guide should be thought of as the final revision of the 
guide. Although a regulatory guide is withdrawn, current licensees may 
continue to use it, and withdrawal does not affect any existing 
licenses or agreements. Withdrawal means that the guide should not be 
used for future NRC licensing activities. Changes to existing licenses 
would be accomplished using other regulatory products.
    Regulatory guides and publicly available NRC documents are 
available electronically through the Electronic Reading Room on the 
NRC's public Web site at: http://www.nrc.gov/reading-rm/doc-collections/. The documents can also be viewed online or printed for a 
fee in the NRC's Public Document Room (PDR) at 11555 Rockville Pike, 
Rockville, Maryland; the mailing address is USNRC PDR, Washington, DC 
20555; telephone: 301-415-4737 or 800-397-4209; fax: 301-415-3548; and 
e-mail: <a href="/cdn-cgi/l/email-protection#ea9a8e98c4988f99859f98898faa849889c48d859c"><span class="__cf_email__" data-cfemail="fe8e9a8cd08c9b8d918b8c9d9bbe908c9dd0999188">[email protected]</span></a>.
    Regulatory guides are not copyrighted, and NRC approval is not 
required to reproduce them.

    Dated at Rockville, Maryland, this 6th day of January 2011.

    For the Nuclear Regulatory Commission.

Harriet Karagiannis,
Acting Chief, Regulatory Guide Development Branch, Division of 
Engineering, Office of Nuclear Regulatory Research.
[FR Doc. 2011-723 Filed 1-13-11; 8:45 am]
BILLING CODE 7590-01-P


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