ML043510336

Use of the University of Maryland'S Letter Report, Thermal-hydraulic Uncertainty Analysis in Pressurized Thermal Shock Risk Assessment, as a Reference in Our NUREG/CR-6859, PRA Procedures and Uncertainty for PTS Analysis

ML043510336
Person / Time
Site:	Beaver Valley, Oconee, Palisades
Issue date:	12/16/2004
From:	Woods H NRC/RES/DRAA, NRC/RES/DRAA/PRAB
To:	David Lew NRC/RES/DRAA, NRC/RES/DRAA/PRAB
References
NUREG/CR-6859
Download: ML043510336 (2)

Text

December 16, 2004 MEMORANDUM TO: David C. Lew, Chief Probabilistic Risk Analysis Branch Division of Risk Analysis and Applications Office of Nuclear Regulatory Research FROM: Hugh W. Woods /RA/

Probabilistic Risk Analysis Branch Division of Risk Analysis and Applications Office of Nuclear Regulatory Research

SUBJECT:

USE OF THE UNIVERSITY OF MARYLANDS (UMDs) LETTER REPORT, THERMAL-HYDRAULIC UNCERTAINTY ANALYSIS IN PRESSURIZED THERMAL SHOCK RISK ASSESSMENT, AS A REFERENCE IN OUR NUREG-CR-6859, PRA PROCEDURES AND UNCERTAINTY FOR PTS ANALYSIS The attached University of Maryland (UMD) report, Thermal-Hydraulic Uncertainty Analysis in Pressurized Thermal Shock Risk Assessment - Methodology and Implementation on Oconee, Beaver Valley, and Palisades Nuclear Power Plants, March, 2003, was provided to me as the NRC/RES Project Manager for our Cooperative Research Agreement K-6007 with UMD.

The report describes methods used to account for uncertainties in the PTS calculations performed by the RES staff and our contractors in re-evaluating PTS risk at U.S. PWRs. As such, the report is cited as a reference in our NUREG/CR-6859 report, PRA Procedures and Uncertainty for PTS Analysis, to be submitted for publication before the end of 2004.

Much of the work described in UMDs report was performed several years ago (our cooperative research agreement with UMD started in August, 1998, and an earlier draft of the report was provided in December, 2001). The attached report includes that earlier work, plus work performed between that time and March, 2003, but of course it does not take into account PTS methods, corrections, and results since that time. Thus, the UMD report may not in all cases be totally consistent with more recent reports such as the staffs NUREG-1806, Technical Basis for Revision of the Pressurized Thermal Shock (PTS) Screening Limit in the PTS Rule (10CFR50.61): Summary Report, to be published by early 2005. If such inconsistencies are noted, the more recent results should be given precedence. However, the UMD report does provide a correct description of the general methods used to account for uncertainties in the PTS calculations, and for that purpose it is cited in NUREG/CR-6859.

Attachment:

UMD Report Distribution: PRAB r/f, DRAA r/f DOCUMENT NAME:G:\PTS\UmdTHuncertRptRefInNUREG.wpd SISP Review Complete OAR in ADAMS? (Y or N) Y ADAMS ACCESSION NO.: TEMPLATE NO. RES- 006 Publicly Available? (Y or N) Y DATE OF RELEASE TO PUBLIC asap SENSITIVE? N To receive a copy of this document, indicate in the box: "C" = Copy without enclosures "E" = Copy with enclosures "N" = No copy OFFICE DRAA/PRAB C DRAA/PRAB DRAA/PRAB NAME HWoods DLew DATE 12/16/04 12/16/04