05000237/LER-2008-004, Re Non-Conservative Core Spray Flow Utilized in LOCA Analysis
| ML081840063 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 06/24/2008 |
| From: | Wozniak D Exelon Generation Co, Exelon Nuclear |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| SVPLTR# 08-0037 LER 08-004-00 | |
| Download: ML081840063 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2372008004R00 - NRC Website | |
text
Exelkn Exelon Generation Company, LLC www.exeloncorp.com Nuclear Dresden Nuclear Power Station 65oo North Dresden Road Morris, I L 60450-9765 10 CFR 50.73 SVPLTR # 08-0037 June 24, 2008 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Dresden Nuclear Power Station, Unit No. 2 Renewed Facility Operating License No. DPR 19 NRC Docket No. 50-237
Subject:
Licensee Event Report 237/2008-004-00, "Non-Conservative Core Spray Flow Utilized in LOCA Analysis" Enclosed is Licensee Event Report 237/2008-004-00, "Non-Conservative Core Spray Flow Utilized in LOCA Analysis," for Dresden Nuclear Power Station Unit 2. This event involves a non-conservative analysis by the fuel vendor (Westinghouse) that affected compliance with the peak cladding temperature requirements stated in 10 CFR 50.46(b)(1). As a result, this event is being reported in accordance with both 10 CFR 50.46(a)(3)(ii) and 10 CFR 50.73(a)(2)(ii)(B),
"The nuclear power plant being in an unanalyzed condition that significantly degraded plant safety." There are no regulatory commitments contained in this submittal.
Should you have any questions concerning this report, please contact Mr. Bob Rybak, Acting Regulatory Assurance Manager, at (815) 416-2800.
Respectfully, David B. Wozniak Site Vice President Dresden Nuclear Power Station Enclosure cc:
Regional Administrator - NRC Region III NRC Senior Resident Inspector - Dresden Nuclear Power Station
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 08/31/2010 (9-2007)
, the NRC may digits/characters for each block) not conduct or sponsor, and a person is not required to respond to, the infnrmatinn mnillr.tinn.
- 13. PAGE Dresden Nuclear Power Station, Unit 2 05000237 1 OF 4
- 4. TITLE Non-Conservative Core Spray Flow Utilized in LOCA Analysis
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
[
- 8. OTHER FACILITIES INVOLVED SEQUEATI R
FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR NEURE NO.
R MONTH DAY YEAR IN/A N/A I4 25_2008_
rFACILITY NAME DOCKET NUMBER 04 25 2008 2008
- - 004-00 06 24 2008 N/A N/A
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
[1 20.2201I(b)
El 20.2203(a)(3)(i)
El 50.73(a)(2)(i)(C)
[I 50.73(a)(2)(vii)
[1 20.2201(d)
El 20.2203(a)(3)(ii)
El 50.73(a)(2)(ii)(A)
[I 50.73(a)(2)(viii)(A)
El 20.2203(a)(1)
El 20.2203(a)(4) 0 50.73(a)(2)(ii)(B)
El 50.73(a)(2)(viii)(B)
[I 20.2203(a)(2)(i)
[I 50.36(c)(1)(i)(A)
El 50.73(a)(2)(iii)
F-50.73(a)(2)(ix)(A)
- 10. POWER LEVEL El 20.2203(a)(2)(ii)
El 50.36(c)(1)(ii)(A)
El 50.73(a)(2)(iv)(A)
[3 50.73(a)(2)(x)
[I 20.2203(a)(2)(iii)
El 50.36(c)(2)
El 50.73(a)(2)(v)(A)
[1 73.71(a)(4) 099 El 20.2203(a)(2)(iv) 0 50.46(a)(3)(ii)
El 50.73(a)(2)(v)(B)
[1 73.71 (a)(5)
El 20.2203(a)(2)(v)
C] 50.73(a)(2)(i)(A)
[I 50.73(a)(2)(v)(C)
[:E OTHER El 20.2203(a)(2)(vi)
E] 50.73(a)(2)(i)(B)
El 50.73(a)(2)(v)(D)
Specify in Abstract below or in This Licensee Event Report is being submitted in accordance with 10 CFR 50.73(a)(2)(ii)(B): 'The nuclear power plant being in an unanalyzed condition that significantly degraded plant safety."
C.
Cause of Event
Based on the results of the cause evaluation performed by Westinghouse, the apparent cause of this error was that the author and verifier of the Westinghouse analysis had an incomplete understanding of the evaluation model, coupled with a false sense of security due both to the bounding system response being essentially the same as the original response and by the fact that the MAPLHGR margin recovery items had been developed by a panel of technical experts.
A contributing cause was that the Exelon SMEs did not adequately challenge why the revised in-shroud core spray leakage values were bounding for Unit 2.
D.
Safety Analysis
The safety significance of the event is minimal. During the duration of the event, Dresden Nuclear Power Station continued to operate within the requirements of the Technical Specifications. The error was limited to the calculation for a postulated scenario. Therefore, the consequences of this event had minimal impact on the health and safety of the public and reactor safety.
E.
Corrective Actions
Corrective actions implemented or planned by Westinghouse include:
Correction of calculation notes, reports, etc. impacted by the non-conservative LPCS flows A quality stand-down with employees to provide lessons learned from the cause evaluation Procedure revision and additional guidance regarding the direction of conservatism and shroud leakages Corrective actions planned by Exelon include:
Training to address identification of critical parameters, and methods to evaluate and minimize risks associated with these critical parameters Reinforcement of importance of technical rigor and questioning attitude
F.
Previous Occurrences
A search was conducted of the Issue Report database for the last two years concerning any LER discussing the area of inadequate design review for plant impact. One previous LER event was found.
05000237/1998-002-00, Unit 2 Reactor Scram From A Main Turbine Trip Due To Inadequate Design Review Performed During Modification The root cause of the Unit 2 scram was found to be inadequate design review during the modification of Yarway level switch replacement. During development of the modification, the impact that the modification would have on plant maintenance activities was not identified by the design team (Design Engineering, Plant Engineering, Maintenance, etc.). The safety significance of the event was minimal since all plant systems operated as designed.
Corrective Action from this event was limited to emphasizing to engineers the necessity of thorough design reviews, detailed industry event database searches, and the need for detailed questioning of maintenance and operations personnel during design scope meetings. This event differs enough in cause that the previous corrective actions would not had prevented the 2008 Westinghouse LBLOCA analysis event.
An OPEX review was also conducted and no events were identified that resulted in further insight for this report.
G.
Component Failure Data
NA