[Federal Register Volume 68, Number 39 (Thursday, February 27, 2003)]
[Notices]
[Pages 9098-9099]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-4624]


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NUCLEAR REGULATORY COMMISSION


Handbook of Parameter Estimation for Probabilistic Risk 
Assessment (PRA)

AGENCY: Nuclear Regulatory Commission (NRC).

ACTION: Announcement of issuance for public comment, availability, and 
public meeting.

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SUMMARY: The U.S. Nuclear Regulatory Commission (NRC) has issued for 
public comment a document entitled ``Handbook of Parameter Estimation 
for Probabilistic Risk Assessment.'' This handbook provides guidance on 
sources of information and methods of estimating distributions of 
parameters used in probabilistic risk assessment. This includes 
determination of both plant-specific and generic estimates for 
initiating event frequencies, component failure rates and 
unavailability, and equipment non-recovery probabilities. Interested 
individuals may obtain a copy of this document from the person 
identified under the caption FOR FURTHER INFORMATION CONTACT.

DATES: Please submit comments by May 23, 2003. Comments received after 
this date will be considered if is practical to do so, but the NRC 
Staff is able to ensure consideration only for comments received on or 
before this date.
    A public meeting will be held on April 2, 2003, from 8:30 a.m. 
until 4:30 p.m. The purpose of this meeting is to discuss the document 
and give guidance for its review and to address external stakeholder 
comments received before the public meeting. The primary authors will 
be available at the public meeting to answer questions and discuss 
items of interest to the public.
    The NRC is interested in receiving comments on specific topics 
reviewers wish to discuss at the public meeting. Reviewers are 
requested to contact Mr. Arthur Salomon at 301-415-6552 or e-mail 
[email protected] by March 21, 2003, with comments or issues they wish to 
have addressed at the public meeting.

ADDRESSES: Please submit comments to Chief, Rules and Directives 
Branch, Office of Administration, U.S. Nuclear Regulatory Commission, 
Washington, DC 20555-0001. Or, you may deliver comments to 11545 
Rockville Pike, Rockville, Maryland, between 7:30 a.m. and 4:30 p.m. 
Federal workdays.
    The public meeting will be held at Two White Flint North, Room T10 
A1, 11545 Rockville Pike, Rockville, Maryland.
    The draft document and certain other documents related to this 
action may be examined in the NRC Public Document Room, 11555 Rockville 
Pike, Public File Area O1 F21, Rockville, Maryland.

FOR FURTHER INFORMATION CONTACT: Arthur D. Salomon, Division of Risk 
Analysis and Applications, Office of Nuclear Regulatory Research, U.S. 
Nuclear Regulatory Commission, Washington, DC 20555-0001. Telephone: 
301-415-6552, e-mail: [email protected].

SUPPLEMENTARY INFORMATION: During the last several years the NRC and 
the nuclear industry have recognized that PRA has evolved to the point 
where it can be used as a tool in the regulatory decision-making 
process. The increased use of PRA has led to the conclusion that the 
PRA scope and model must be commensurate with the applications. Several 
procedural guides and standards (such as the ``Standard For 
Probabilistic Risk Assessment For Nuclear Power Plant Applications'' 
published by The American Society of Mechanical Engineers in 2002) have 
been and are being developed that identify requirements for the PRA 
models. This handbook was prepared to supplement these documents. It 
provides a compendium of good practices that a PRA analyst can use to 
develop parameter distributions required for quantifying PRA models. It 
complements the ASME PRA Standard by providing guidance for estimation 
of parameters related to initiating events; by describing statistical 
techniques for estimating parameters used in analysis

[[Page 9099]]

of basic events such as equipment failures; and by addressing methods 
for estimating equipment unavailability. Furthermore, the handbook 
includes appendices describing the basics of probability and statistics 
used in performing the more detailed analyses discussed in the main 
portion of the document.
    The handbook provides the basic information needed to generate 
estimates of the parameters commonly used in PRA analysis. It begins by 
describing the probability models and plant data used to evaluate each 
of the parameters. Possible sources for the plant data are identified 
and guidance on the collection, screening, and interpretation is 
provided. The statistical techniques (both Bayesian and classical 
methods) required to analyze the collected data and test the validity 
of statistical models are described. Examples are provided to help the 
PRA analyst utilize the different techniques. The handbook also 
provides advanced techniques that address modeling of time trends. 
Methods for combining data from a number of similar, but not identical 
sources are also provided. This includes empirical and hierarchical 
Bayesian approaches. Examples are provided to guide the analyst. The 
handbook does not provide guidance on parameter estimation for all of 
the events included in a PRA. Specifically, common cause failure and 
human error probabilities are not addressed. In addition, guidance is 
not provided regarding the use of expert elicitation. However, 
suggested references regarding these technical areas are provided in 
the handbook introduction.

    Dated at Rockville, Maryland, this 21st day of February, 2003.

    For the Nuclear Regulatory Commission.
Scott F. Newberry,
 Director, Division of Risk Analysis and Applications, Office of 
Nuclear Regulatory Research.
[FR Doc. 03-4624 Filed 2-26-03; 8:45 am]
BILLING CODE 7590-01-P