ML18260A290
| ML18260A290 | |
| Person / Time | |
|---|---|
| Issue date: | 10/19/2018 |
| From: | Raymond Furstenau NRC/RES/DRA/PRAB |
| To: | Ho Nieh Office of Nuclear Reactor Regulation |
| Sancaktar S | |
| References | |
| NRR-2010-005 | |
| Download: ML18260A290 (3) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 MEMORANDUM TO:
Ho K. Nieh, Director Office of Nuclear Reactor Regulation FROM:
Raymond V. Furstenau /RA/
Director of Nuclear Regulatory Research
SUBJECT:
CLOSEOUT OF USER NEED REQUEST NRR-2010-005, SUPPORT IN DEVELOPING ANALYTICAL BASES AND GUIDANCE FOR FUTURE RISK ASSESSMENTS OF CONSEQUENTIAL STEAM GENERATOR TUBE RUPTURE (C-SGTR) EVENTS The Office of Nuclear Regulatory Research (RES) has completed the work requested by the Office of Nuclear Reactor Regulation (NRR) under User Need Request (UNR) NRR-2010-005, Support in Developing Analytical Bases and Guidance for Future Risk Assessments of C-SGTR Events. This memorandum documents the closure of UNR NRR-2010-005 as RES has provided NRR with the completed reports, guidance, and tools as requested and as noted in Table 1 below.
The research described under UNR NRR-2010-005 encompassed four broad areas:
- 1. Further thermal-hydraulic analyses to address Combustion Engineering (CE) plants and the impact of in-core instrument tube failures on natural circulation.
- 2. Develop updated steam generator (SG) flaw distributions and enhanced reactor coolant system (RCS) structural analyses.
- 3. Develop guidance and tools for future risk assessments.
- 4. Prepare a document summarizing key research.
Work was performed by RES staff in the Division of Systems Analysis (DSA), the Division of Engineering (DE), and the Division of Risk Analysis (DRA), supported by contractors as needed.
RES had a number of meetings with the Advisory Committee on Reactor Safeguards (ACRS) on the C-SGTR work and ACRS member comments were received and addressed by the staff.
On May 19, 2017, a favorable ACRS letter (ML17138A017) was issued, recommending publishing the report. NUREG-2195, Consequential SGTR Analysis for Westinghouse and Combustion Engineering Plants with Thermally Treated Alloy 600 and 690 Steam Generator Tubes, was published in March 2018.
CONTACT: Selim Sancaktar, RES/DRA/PRAB 301-415-2391 October 19, 2018
2 The main conclusion from this work is that the SG geometry and the fluid flow rates in different SG designs can significantly influence the potential likelihood of C-SGTRs. For the cases studied, SG designs with a shallow inlet plenum (resulting in the tubesheet located closer to the hot leg inlet) and a shorter hot leg can result in a greater likelihood of a C-SGTR following a core damage event associated with accident conditions that challenge SG tubes. A shallow inlet plenum design reduces the mixing of hot gases entering the SG, thereby creating a higher thermal load on the tubes. For the specific replacement SG geometries analyzed in this study, the Combustion Engineering plant design had an increased likelihood of a C-SGTR and a higher potential for a large early release, than the Westinghouse plant design.
The work done and documents created are summarized in Table 1 below. The main deliverables were:
NUREG-2195, Consequential SGTR Analysis for Westinghouse and Combustion Engineering Plants with Thermally Treated Alloy 600 and 690 Steam Generator Tubes Risk Assessment Standardization Process (RASP) RASP Handbook Volume 5 section on C-SGTR Table 1. RES and NRR Output Related to the Work Request Document Provided to NRR ADAMS ML#
Publicly Available Comment NUREG-2195 Yes ML18122A012 Yes RASP Handbook Section on C-SGTR Yes ML18011A027 Yes Draft. For public comments C-SGTR Calculator Yes ML18178A139 Yes Contains software, examples, and documents. Being made public under a separate internal memorandum.
C-SGTR User Manual Yes ML18171A275 Yes 2018 enhanced version.
Contains software, examples, and instructions. Being made public under a separate internal memorandum.
ISL Basis Report and Calculator User Manual Yes ML15054A495 Yes 2012 ISL Flaw Report Yes ML15054A504 Yes 2012 C-SGTR Paper in PSAM 14 2018 Conference Yes ML18074A025 Yes Presented in 2018 PSAM 14 conference.
C-SGTR Paper in PSA 2013 Conference Yes ML15054A177 Only in Conference proceedings Presented in PSA 2013 conference. ADAMS version not publicly available.
RES has established an online quality survey to collect feedback from user offices on the usefulness of RES products and services. This survey can be found online at the hyperlink:
http://fusion.nrc.gov/res/team/OfficeWide/Lists/RES%20Product%20Quality%20Survey/overvie w.aspx. I would appreciate it if you would see that this shortabout 5 minutessurvey is completed by the responsible manager or supervisor within the next 10 working days to present your offices views of the delivered RES product.
ML18260A290 OFFICE RES/DRA/PRAB BC:RES/DRA/PRAB D:RES/DE D:RES/DSA D:RES/DRA D:RES NAME S. Sancaktar*
J. Nakoski*
B. Thomas M. Case M. Cheok R. Furstenau DATE 9/18/2018 9/28/2018 10/03/2018 10/04/2018 10/16/2018 10/19/2018