ML040290388
| ML040290388 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 01/29/2004 |
| From: | Southern Nuclear Operating Co |
| To: | Office of Nuclear Reactor Regulation |
| Peters S, NRR/DLPM, 415-1842 | |
| References | |
| EA-03-009, TAC MC1519 | |
| Download: ML040290388 (16) | |
Text
Joseph M. Farley Nuclear Plant 0
0 Reactor Vessel Head Penetration w
Nozzle Inspection Relaxation Unit 2 Spring 2004 -2R16 Mike Stinson Vice President Southern Nuclear 1
Agenda
- 1. Introduction and Purpose
- 2. NRC Order EA-03-009 Overview.
Safety Issues
- Inspection Requirements
- 3. SNC Response to Order
- 4. Specific FNP 2R1 6 Relaxation Request
- 5. Basis for FNP 2R16 Relaxation Request
- 6. FNP 2R16 Spring 2004 Inspection Plans
- 7. Summary
- 8. NRC Feedback 2
- 1. Introduction and Purpose
- Discuss NRC Order requirements
- Discuss Farley's reactor vessel head inspection history and results
- Discuss specific relaxation request for 2R1 6, basis for request, and inspection plans
- Receive NRC feedback on relaxation request 3
- 2. NRC Order EA-03-009
- Safety Issues
- Corrosion of the RPV head
- Nozzle ejection
- Inspection Requirements - each outage
- RPV head bare metal visual
- Penetration nozzle non-visual NDE 4
- 3. SNC Response to Order
- SNC consented to the Order
- SNC also requested relaxation of the required inspection coverage due to the physical limits imposed by:
"Footprint" of the CRDM shroud on the head Configuration of the nozzle bottoms (OD thread and ID taper)
- NRC approved the requested relaxation
- An Order revision reflecting these generically applicable relaxations is expected soon 5
- 4. Specific U2R16 Relaxation Request
- Farley will perform IV. C.(1)(a), bare metal visual of the RPV head
- Relaxation is requested to not perform non-visual examination per Item IV.C.(1)(b)
- Relaxation is requested per Order Item IV.F.(2) because compliance would result in hardship without a compensating increase in safety
- The hardship entailed is an estimated 4.1 Rem of additional radiation exposure to inspection personnel 6
- 5. Basis for Relaxation Request
- Cracks through either the nozzle or J-groove weld can cause corrosion only after they reach the nozzle annulus area.
- Corrosion products occupy more volume than the steel corroded and therefore are forced to the head surface.
- Bare metal visual inspection will detect corrosion products on the head surface.
7
- 5. Basis for Relaxation Request (continued)
- Fall 2002 2R1 5 bare metal visual inspection of the head and UT exam of the nozzles detected no evidence of cracks.
- Analysis demonstrates that nozzle cracks propagating from below the examined volume (or from flaws within the examined volume too small to detect) would take >2 operating cycles to cause leakage.
- Industry experience shows that leakage over multiple operating cycles is required for head corrosion to threaten a LOCA.
8
- 5. Basis for Relaxation Request (continued)
- Unit 2 head replacement is planned for fall 2005 at 2R17.
- Analysis demonstrates that about 12 cycles of operation are needed for a circumferential crack to threaten nozzle ejection.
- Only 2 cycles will have elapsed since the last nozzle UT in fall 2002 (2R15) when the planned head replacement occurs in fall 2005 (2R1 7)
- 5. Basis for Relaxation Request (continued)
Unit 2 has injected zinc into the RCS for
>5 years; SNC believes this has mitigated initiation of PWSCC (as has been shown by laboratory testing).
- Unit 2 will have accrued fewer EDY at 2R1 6 (16.8 EDY) than Unit 1 had when found crack-free by BMV and UT examination per the Order in spring 2003 at 1 R1 8 (17.5 EDY).
10
5 U Basis for Relaxation Request Summary
- Bare metal visual will address the RPV head corrosion safety concern
- corrosion products will appear on the RPV head
- industry experience demonstrates multiple operating cycles are required to threaten a LOCA
- Analysis shows NDE each outage is not needed to address nozzle ejection safety concern
- circumferential cracking requires about 12 cycles to threaten nozzle ejection 11
- 6. Farley Unit 2 Spring 2004 Inspection Plans
- Farley will perform a bare metal visual inspection of the outer surface of the RPV top head per Order Item IV.Ca(1 )(a).
- Absent approval of the requested relaxation of the Order, Farley will perform UT examination of the RPV penetration nozzles per option IV.C.(1 )(b)(i).
- Farley will also perform a visual examination of the outer surface of the RPV bottom head. as. described in SNC's response to NRC Bulletin 2003-02.
12
- 7. Summary
- Performing only a bare metal visual inspection provides adequate assurance that the safety concerns of Order EA-03-009 are met.
- This is supported by the previous crack-free inspection history and crack propagation time analyses for FNP Unit 2.
- Performance of non-visual NDE during the spring 2004 Unit 2 outage (2R1 6) would therefore impose a hardship (4.1 Rem dose to inspection personnel) without a compensating increase in the level of quality and safety.
- 8. NRC Feedback
- SNC's Technical Approach
- NRC's Review Schedule
- Projected Decision Date (2R1 6 Outage Starts 3/13/2004) 14
4' Dia. Penotraflon Nozzle Minimum
\\ Interference Fit Zone J-Groove Weld O.D. Thread I Minimum Cladding Approx Lower Limit of UT Coverwage I.D. Taper
- .8;;
Penetration nozzle volume I'j W covered by UT exam during L.
- fall 2002 outage 2R15 NOT TO SCALE FNP UNIT 2 TYPICAL PENETRATION NOZZLE CROSS-SECTION
200 NRC Bulletins Issued 2002-01 1-01 2002-02 1R17 21 1l 1
NRC Order EA-03-009 Issued 5
lR18 I
I 2R16 2R14 Al U1 1R19 2R17 l
l I
I 1S1 1S6 S
I-n 2001 2002
.2003 Performed Unit 2 Best-Effort BMV Head Inspection Performed Unit 2 100% BMV Head Inspection and Nozzle UT Exam I
2004 Relaxation Requested to Perform Only 100% BMV on Unit 2 2005 2006 Planned Unit 2 RPV Head Replacement Performed Unit 1 100% BMV Head Inspection Performed Unit 1 100% BMV Head Inspection and Nozzle UT & ECT Exams Planned Unit 1 RPV Head Replacement Farley Nuclear Plant Units 1 & 2 RPV Closure Head Inspection and Replacement Timeline