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Draft NUREG/CR: Issuance, Availability

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Nuclear Regulatory Commission.

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Notice of Issuance and Availability of Draft NUREG/CR, “Diversity Strategies for Nuclear Power Plant Instrumentation and Control Systems.”

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Michael E. Waterman, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, telephone: (301) 251-7451 or e-mail to

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I. Introduction

The U.S. Nuclear Regulatory Commission (NRC) is issuing for public comment a draft contractor report in the agency's “NUREG/CR” series. This series was developed to describe and make available to the public information such as the results of research conducted on behalf of the NRC regarding specific approaches for implementing safety systems in accordance with NRC regulations.

The draft contractor report (NUREG/CR), entitled, “Diversity Strategies for Nuclear Power Plant Instrumentation and Control Systems,” is temporarily identified as “Diversity NUREG/CR”, which should be mentioned in all related correspondence.

This report presents the technical basis for establishing acceptable mitigating strategies that resolve diversity and defense-in-depth (D3) assessment findings and conform to NRC requirements. The research approach employed to establish appropriate diversity strategies involves investigation of available documentation on D3 methods and experience from nuclear power and nonnuclear industries, capture of expert knowledge and lessons learned, determination of commonalities in diversity approaches, and assessment of the nature of common-cause failures (CCFs) and compensating diversity attributes. Succinctly, the purpose of the research described in this report was to answer the question, “If diversity is needed in a safety system to mitigate the consequences of potential CCFs, how much diversity is enough?”

The grouping of diversity criteria combinations establishes baseline diversity usage and facilitates a systematic organization of strategic approaches for coping with CCF vulnerabilities. These baseline sets of diversity criteria constitute appropriate CCF mitigating strategies for digital safety systems. The strategies represent guidance on acceptable diversity usage and can be applied directly to ensure that CCF vulnerabilities identified through a D3 assessment have been adequately resolved. Additionally, a framework has been generated for capturing practices regarding diversity usage. A metric has been developed for the systematic assessment of the comparative effect of proposed diversity strategies on the basis of these practices (see Appendix A).

II. Further Information

The NRC staff is soliciting comments on Diversity NUREG/CR. Comments may be accompanied by relevant information or supporting data and should mention “Diversity NUREG/CR” in the subject line. Comments submitted in writing or in electronic form will be made available to the public in their entirety through the NRC's Agencywide Documents Access and Management System (ADAMS).

Personal information will not be removed from your comments. You may submit comments by any of the following methods:

1. Mail comments to: Rulemaking Directives Branch, Office of Administration, U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001.

2. E-mail comments to:

3. Fax comments to: Rulemaking and Directives Branch, Office of Administration, U.S. Nuclear Regulatory Commission at (301) 492-3446.

Requests for technical information about Diversity NUREG/CR-xxxx may be directed to the NRC contact, Michael E. Waterman at (301) 251-7541 or e-mail to

Comments would be most helpful if received by July 10, 2009. Comments received after that date will be considered if it is practical to do so, but the NRC is able to ensure consideration only for comments received on or before this date. Although a time limit is given, comments and suggestions in connection with items for inclusion in the Diversity NUREG/CR currently being developed or improvements in the NUREG/CR are encouraged at any time.

Electronic copies of Diversity NUREG/CR are available in ADAMS (​reading-rm/​adams.html), under Accession No. ML090510113.

In addition, the draft Diversity NUREG/CR is available for inspection at the NRC's Public Document Room (PDR), which is located at 11555 Rockville Pike, Rockville, Maryland. The PDR's mailing address is USNRC PDR, Washington, DC 20555-0001. The PDR can also be reached by telephone at (301) 415-4737 or (800) 397-4205, by fax at (301) 415-3548, and by e-mail to

NUREG/CRs are not copyrighted, and Commission approval is not required to reproduce them.

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Dated at Rockville, Maryland, this 3rd day of June 2009.

For the Nuclear Regulatory Commission.

Stuart A. Richards,

Deputy Director, Division of Engineering, Office of Nuclear Regulatory Research.

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[FR Doc. E9-13708 Filed 6-10-09; 8:45 am]