ML062990478
| ML062990478 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 10/24/2006 |
| From: | Martin R NRC/NRR/ADRO/DORL/LPLII-2 |
| To: | South Carolina Electric & Gas Co |
| Martin RE, NRR/DLPM, 415-1493 | |
| Shared Package | |
| ML062910160 | List: |
| References | |
| TAC M96872 | |
| Download: ML062990478 (4) | |
Text
Introduction Reason for Commitment Change
" Management Challenge
- Design Change Package late issue
- Planning & Scheduling not timely
- Implementation Resources
" Risk of implementing Design Change
- Risk of impact to SW supply to RBCU function without corresponding risk improvement from design change Plant Safety in Current Configuration VCSNS will remain safe:
- Water hammer condition exists only when SW aligned to RBCU's and LOOP
- PRA indicates very low risk (1.74E-07/yr)
- Phase 1 actions in place
- Real Life Experience
- No damage to piping or hangers
I Schedule for Design Change Implementation (Commitment change required)
Implementation by 5/2008 (Refueling 17)
- Extensive modification
- Unit shutdown required
- Next scheduled shutdown for refueling Resolution of Technical Issues from NRC letter August 22, 2006
" VCSNS reviewed NRC ltr. dated 8/22/2006
" No additional explanation necessary
" VCSNS expects to respond in the next 60 days
Introduction Purpose of Visit
" Discuss VCSNS commitments associated with Generic Letter (GL) 96-06.
Implement design changes by 10/06
- 1. Delay opening 3107A/B
- 2. Install vacuum relief valves
- 3. Replace 3107AJB
" VCSNS wishes to alter this commitment FIGURE 2a Modification WWIl Coilutkrain - RBCUs aligned With SW sysem WATER HAMAMER 14110A110N
-hAM 1.WU 2.W-SMMSWSPq upmd~ard rg.~mdSWBP PHASE 1 -LOOPo.,an SW b-W P.W. W d-OLW PHASE 2 - VW. 3107A fttdo-8Wd kqP PHASE 32-SAMd IotM SMW 310A IA Need I -NSWH PHASES. ý1 31OIAISE.W 1.SW 301 IC Stupy va*,m.IiI HA.
-lc cu ~
- MI "TO,SW Pond
V. C. Summer Nuclear Station Generic Letter 96-06 Discussion Brad Stokes, Manager Design Engineering Alan Torres, Manager Planning and Scheduling Chuck Barbier, Principle Design Engineer - Piping CM
ýe ýZý Agenda
- Introduction
- Plant Safety in Current Configuration
- Schedule for Implementation of Modifications
- Resolution of Technical Issues
- Open discussion I
NRC/VCSNS Open Discussion
FIGURE 2a Modification Inital Configuration - RBCUs aligned with SW system 3109A WATER HAMMER MITIGATION - Mod to install:
XAA-1
- 1. vacuum relief valve downstream of 3107A
- 2. replace 3107A with an air operated butterfly valve that fast closes upon de-energize ofSWBP 3108B 3109B
- 3. delay opening of valve 3107A for five seconds after start of SWBP XAA-I B Lý PHASE 1 - LOOP occurs causing SW booster pumps to de-energize.
PHASE 2 - Valve 3107A fast closes and traps Column of fluid above it PHASE 3 - Void formed below 3107A is filled with air by vacuum relief valves PHASE 4 - After 41 seconds, SW booster pumps re-energized, 3107A valve 5 sec delayed opening allows fluid flow momentum to build preventing further void formation PHASE 5 - air void downstream 3107A flushed to SW pond Fast closing valve traps water above it Vacuum Relief Valve
'A IAA SW Booster De-energized to LOOP Pump SW Supply Idue IC Supply IC Return Vacuum relief valve replaces vacuum void To SW with air Pond