ML091890814
| ML091890814 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom, Surry  |
| Issue date: | 08/03/2009 |
| From: | Christiana Lui NRC/RES/DRA |
| To: | Cunningham M NRC/NRR/DRA |
| Helton, Don, RES/DRA, 301-251-7594 | |
| Shared Package | |
| ML091890792 | List: |
| References | |
| NRR-2008-007 | |
| Download: ML091890814 (4) | |
Text
August 3, 2009 MEMORANDUM TO:
Mark A. Cunningham, Director Division of Risk Assessment Office of Nuclear Reactor Regulation FROM:
Christiana H. Lui, Director /RA/
Division of Risk Analysis Office of Nuclear Regulatory Research
SUBJECT:
RESPONSE TO USER NEED REQUEST NRR-2008-007, ITEMS 1.d AND 1.f, THERMAL HYDRAULIC SUCCESS CRITERIA UPDATE The response to User Need Request NRR-2008-007 (available in ADAMS at accession no.
ML082910527) commits to providing the Office of Nuclear Reactor Regulation (NRR) with an overview of completed thermal-hydraulic analysis for Surry and Peach Bottom nuclear power plants. The Office of Nuclear Regulatory Research (RES) has performed thermal-hydraulic analysis to investigate particular sequences at these two plants for the purpose of updating specific success criteria (and other event tree characteristics) for the associated Standardized Plant Analysis Risk (SPAR) models. Preliminary results were provided to you via a February 2009 memorandum (ML090410204). In addition, briefings on this effort have been provided to you and your staff (May 2008, December 2008, March 2009), the public (March 2009 Regulatory Information Conference - RIC), and the Senior Risk Analysts (May 2008, May 2009).
The project has also been routinely discussed during Risk Assessment Standardization Project User Group meetings.
The enclosure to this memorandum provides the final results. This memorandum closes out the previously defined thermal-hydraulic analysis aspects of items 1.d and 1.f of the subject user need, with subsequent update of the relevant SPAR models planned for Fiscal Year 2010.
Having said that, we are aware that additional analysis in this area is desired, and we are working with your staff to define a path forward, which may be formalized in a revised or new user need request.
The enclosure provides the following information:
Introduction and background information.
The basis for the core damage definition employed.
Major plant characteristics for Surry and Peach Bottom.
A description of the two MELCOR models used.
Results of numerous MELCOR calculations based on a calculation matrix jointly developed by NRR and RES staff, with input from the Idaho National Laboratory.
CONTACT:
Donald M. Helton, RES/DRA (301) 251-7594
Expected application of the MELCOR results to Surry and Peach Bottom SPAR models.
Planned future work.
Specifically, the enclosure documents the large body of MELCOR calculations performed and translates these analyses into specific candidate SPAR model upgrades for Surry and Peach Bottom, as follows:
Surry:
o Better quantification of the timing of core damage relative to refueling water storage tank depletion for small break loss-of-coolant accidents (LOCAs).
o Confirmation of the success criteria for small LOCAs without operator action.
o Revision of the success criteria for feed & bleed (loss of all feedwater) to require fewer power-operated relief valves.
o Updated timings for steam generator tube rupture events with minimal operator action.
o Updated timings for alternating current (ac) power recovery for station blackout sequences.
o Revision of success criteria for medium and large break LOCAs to modify the systems needed.
Peach Bottom:
o Additional credit for the reactor core isolation cooling system during an inadvertent /
stuck-open relief valve event, and potential additional credit for the control rod drive injection system.
o Updated timings for suppression pool heatup and ac power recovery for station blackout sequences.
In some cases, the above results can be applied to other similar plants, as discussed further in the enclosure. To date, these results have not been made publicly available (the 2009 RIC presentation did not include results). To facilitate further work in this area and transparency, we intend to issue the enclosure as a publicly available document 60 days after issuance of this memorandum.
We will continue to work with your staff to address additional design types and/or additional scenarios. We also plan to engage with the Electric Power Research Institute on this initiative and to present results at (a) a September 2009 meeting of the MELCOR Code Assessment Program and (b) a December 2009 meeting of the Modular Accident Analysis Program Users Group.
Lastly, we would like to extend our appreciation to your past and present staff, particularly Donald Dube, for their important contributions to this work.
Please share the enclosure with others in NRR and the Regions who would find it of interest.
Enclosure:
Thermal-Hydraulic Analysis to Support Update of Specific Success Criteria in the Standardized Plant Analysis Risk Model, Version 2.0, July 2009
ML091890792 OFFICE RES/DRA/PRAB SUNSI Review RES/DSA/FSTB RES/DRA/PRB BC:
RES/DRA/PRAB NAME DHelton DHelton HEsmaili DMarksberry KCoyne DATE 07/14/09 07/21/09 07/14/09 07/17/09 07/24/09 OFFICE BC:
RES/DSA/FSTB Technical Edit D: RES/DSA D: RES/DRA NAME RLee JZabel (via email)
JUhle CLui DATE 07/14/09 07/10/09 07/20/09 08/03/09