[Federal Register Volume 60, Number 218 (Monday, November 13, 1995)]
[Notices]
[Page 57026]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-27918]



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NUCLEAR REGULATORY COMMISSION

Availability of NRC Iterative Performance Assessment Phase 2: 
Development of Capabilities for Review of a Performance Assessment for 
a High-Level Waste Repository

AGENCY: Nuclear Regulatory Commission.

ACTION: Notice of availability.

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SUMMARY: The Nuclear Regulatory Commission is announcing the 
availability of NUREG-1464, ``NRC Iterative Performance Assessment 
(IPA) Phase 2: Development of Capabilities for Review of a Performance 
Assessment for a High-Level Waste Repository.''

ADDRESSES: Copies of NUREG-1464 can be purchased from the 
Superintendent of Documents, U.S. Government Printing Office, P.O. Box 
37082, Washington, DC 20013-7082. Copies are also available from the 
National Technical Information Service, 5285 Port Royal Road, 
Springfield, VA 22161. A copy of NUREG-1464 is also available for 
public inspection and/or copying at the NRC Public Document Room, 2120 
L Street (Lower Level), NW., Washington, DC 20555-0001.

FOR FURTHER INFORMATION CONTACT: Michael P. Lee, Performance Assessment 
and Hydrology Branch, Division of Waste Management, Office of Nuclear 
Material Safety and Safeguards, Nuclear Regulatory Commission, 11545 
Rockville Pike, MD 20852-2738. Telephone: (301) 415-6677.

SUPPLEMENTARY INFORMATION: This report describes the results of the 
second phase of the development of the NRC staff's capability to review 
a performance assessment for a geologic repository. This capability, 
developed with the assistance of its contractor (the Center for Nuclear 
Waste Regulatory Analyses--the CNWRA), helps the NRC staff assess 
whether the U.S. Department of Energy's (DOE's) site characterization 
activities are adequate, during the pre-licensing phase, and, later, 
will help the staff review a license application for the potential 
geologic repository for spent nuclear fuel and other high-level 
radioactive waste (HLW) at Yucca Mountain, NV.
    As its name indicates, IPA involves repeated iterations directed at 
improving both the NRC staff's capability for reviewing DOE's 
demonstration of repository performance and the staff's understanding 
of combined systems and events and processes that are key to repository 
performance. In addition, IPA is intended to support timely feedback to 
DOE on their licensing strategy, site characterization, and design 
programs. Performance assessment of a geologic repository, like other 
systematic safety-assessment methodologies, benefits substantially by 
being conducted in an iterative manner, primarily because the lessons 
learned regarding modeling improvements, data needs, and methodology 
can be addressed in subsequent iterations.
    The IPA Phase 2 demonstration made use of the scenario selection 
procedure developed by Sandia National Laboratories and modified by the 
NRC staff to provide a set of scenarios, with corresponding 
probabilities, for use in the consequence analysis of a potential HLW 
disposal site in unsaturated tuff. Models of release of radionuclides 
from the waste form and transport in ground water, air and by direct 
pathways provided preliminary estimates of releases to the accessible 
environment for a 10,000 year period. The input values of parameters 
necessary for the consequence models were sampled numerous times using 
Latin Hypercube Sampling from probability distributions. The results 
from the consequence models were then used to generate Complementary 
Cumulative Distribution Functions (CCDFs) for either normalized 
radionuclide release to the accessible environment or effective dose 
equivalents to a target population. CCDFs were calculated for 
probabilistically significant combinations (scenarios) of four 
disruptive events; exploratory drilling, pluvial climate, seismicity, 
and magmatism. Sensitivity and uncertainty analyses of the calculated 
releases and effective dose equivalents were also used to determine the 
importance of the parameters.
    Because of the preliminary nature of the analysis and data base, 
the results and conclusions presented in NUREG-1464 should be carefully 
interpreted. They should not be misconstrued to represent the actual 
performance of the proposed Yucca Mountain repository nor serve as an 
endorsement of the methods used.

    Dated at Rockville, Maryland, this 30th day of October 1995.

    For the Nuclear Regulatory Commission.
John H. Austin,
Chief, Performance Assessment and Hydrology Branch, Division of Waste 
Management, Office of Nuclear Material Safety and Safeguards.
[FR Doc. 95-27918 Filed 11-9-95; 8:45 am]
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