05000346/LER-2014-004, Regarding Deficiency in Loss of Coolant Accident Analysis Adversely Affected Predicted Peak Cladding Temperature
| ML15028A192 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 01/23/2015 |
| From: | Lieb R FirstEnergy Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| L-15-003 LER 14-004-00 | |
| Download: ML15028A192 (4) | |
| 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 |
| 3462014004R00 - NRC Website | |
text
FENOCT FirstEnergy Nuclear Operating Company 5501 North State Route 2 Oak Harbor, Ohio 43449 Raymond A. ILieb Vice President, Nuclear January 23, 2015 419-321-7676 Fax: 419-321-7582 L-1 5-003 10 CFR 50.73 ATTN: Document Control Desk United States Nuclear Regulatory Commission Washington, D.C. 20555-0001
SUBJECT:
Davis-Besse Nuclear Power Station Docket Number 50-346, License Number NPF-3 Licensee Event Report 2014-004 Enclosed is Licensee Event Report (LER) 2014-004, "Deficiency in Loss of Coolant Accident Analysis Adversely Affected Predicted Peak Cladding Temperature." This LER is being reported in accordance with 10 CFR 50.73(a)(2)(ii)(B).
There are no regulatory commitments contained in this letter or its enclosure. The actions described represent intended or planned actions and are described for information only. If there are any questions or if additional information is required, please contact Mr. Patrick J. McCloskey, Manager, Site Regulatory Compliance, at (419) 321-7274.
Since. ly, Raymond A. Lieb GMW Enclosure: LER 2014-004 cc:
NRC Region III Administrator NRC Resident Inspector NRR Project Manager Utility Radiological Safety Board K;)-
j'J
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 EXPIRES 0113112017 (02-2014)
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. PAGE Davis-Besse Nuclear Power Station 05000 346 1 OF 3
- 4. TITLE Deficiency in Loss of Coolant Accident Analysis Adversely Affected Predicted Peak Cladding Temperature
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED SEQUENTIAL REV FACILITY NAME DOCKET NUMBER MONTH YEAR YEAR NUMBER NO.
MONTH DAY YEAR 05000 01 FACILITY NAME DOCKET NUMBER 11 25 2014 2014 004 00 01 23 2015 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
E] 20.2201(b)
El 20.2203(a)(3)(i)
C1 50.73(a)(2)(i)(C)
[I 50.73(a)(2)(vii)
El 20.2201(d)
El 20.2203(a)(3)(ii)
Dl 50.73(a)(2)(ii)(A)
El 50.73(a)(2)(viii)(A)
E] 20.2203(a)(1)
El 20.2203(a)(4)
Z 50.73(a)(2)(ii)(B)
El 50.73(a)(2)(viii)(B)
El 20.2203(a)(2)(i)
El 50.36(c)(1)(i)(A)
El 50.73(a)(2)(iii)
El 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL El 20.2203(a)(2)(it)
[] 50.36(c)(1)(ii)(A)
E] 50.73(a)(2)(iv)(A)
El 50.73(a)(2)(x)
El 20.2203(a)(2)(iii)
El 50.36(c)(2)
El 50.73(a)(2)(v)(A)
[I 73.71(a)(4)
El 20.2203(a)(2)(iv)
[I 50.46(a)(3)(ii)
El 50.73(a)(2)(v)(B)
El 73.71 (a)(5) 1] 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A)
El 50.73(a)(2)(v)(C)
[E OTHER E] 20.2203(a)(2)(vi)
El 50.73(a)(2)(i)(B)
El 50.73(a)(2)(v)(D)
Specify in Abstract below or in l
Ia
DESCRIPTION OF EVENT
On October 20, 2014, the fuel vendor (AREVA) for the Davis-Besse Nuclear Power Station (DBNPS) notified the FirstEnergy Nuclear Operating Company (FENOC) of a potential issue regarding Loss of Coolant Accident (LOCA) modeling. This issue, which potentially affected the operations of all Babcock and Wilcox (B&W) designed plants, involved the fuel pellet thermal conductivity model and associated conservatisms in the Large Break LOCA model. For the DBNPS, which was operating in Mode 1 at approximately 100 percent full power for the duration of this issue, adequate margin existed in the reactor core operating limits to accommodate temporary compensatory measures, in the form of restricted operating limits, while further evaluations were being performed.
On October 21, 2014, the fuel vendor transmitted temporary conservative limits on Power Peaking Factor Fq and Axial Power Imbalance (as measured by the Out-of-Core Neutron Detectors) for the DBNPS. The guidance provided by the fuel vendor recommended the Fq limits for higher burnup fuel assemblies be reduced, confirmed the limits on Axial Power Imbalance (as determined by the Incore Detector System) did not need to be changed due to conservatism built into the limits, and recommended that at less than 92 percent full power the limits on Axial Power Imbalance as determined from the out-of-core neutron detectors be reduced. This guidance was implemented at the DBNPS on October 23, 2014.
On November 25, 2014, the fuel vendor notified FENOC of the final evaluation results for the deficiency discovered in the thermal conductivity model computer codes. Accounting for the deficiency resulted in the predicted analytical Peak Cladding Temperature (PCT) increasing to 2513 degrees F during Large Break LOCA conditions. This 2513 degrees F exceeded the DBNPS licensing basis PCT of 2200 degrees F for compliance with 10 CFR 50.46(b)(1). Because of the recommended compensatory measures implemented on October 23, 2014, the deficiency had no impact on current plant operation or public health and safety.
CAUSE OF EVENT
The cause of this event was related to the evolution of the fuel vendor's modeling. The fuel vendor's previous models for fuel rod thermal mechanical performance inadequately addressed the thermal conductivity degradation effect. The deficiency was identified while developing new computer models, which utilized updated data and incorporated a greater understanding of the fuel rod thermal mechanical performance.
ANALYSIS OF EVENT
A methodology was developed by FENOC in collaboration with the fuel vendor to evaluate past core operating data. Implementation of this methodology determined that there were no actual fuel assembly power peaks observed during the last three years that would have resulted in peak clad temperatures in excess of analysis of record peak clad temperatures. Therefore, this issue was of very low safety significance.
Reportability Discussion:
The NRC was verbally notified of this event per 10 CFR 50.72(b)(3)(ii)(B) at 1632 hours0.0189 days <br />0.453 hours <br />0.0027 weeks <br />6.20976e-4 months <br /> on November 25, 2014, via Event Number 50639. This issue is being reported in accordance with 10 CFR 50.73(a)(2)(ii)(B) as an unanalyzed condition that significantly degraded plant safety. Notification of the Defect in the LOCA Analysis in accordance with 10 CFR 21 was completed by the fuel vendor by letter dated December 16, 2014 (Agencywide Documents Access and Management System (ADAMS)
Accession No. ML14351A308).
CORRECTIVE ACTIONS
On December 19, 2014, notification of the error and change that affected the Large Break LOCA analysis for the DBNPS was submitted to the NRC in accordance with 10 CFR 50.46(a)(3)(ii) via FENOC letter L-14-403 (ADAMS Accession No. ML14353A228). This letter includes the schedule for the LOCA reanalysis and submittal to the NRC as required by 10 CFR 50.46.
PREVIOUS SIMILAR EVENTS
There have been no Licensee Event Reports submitted for the DBNPS in the past three years documenting deficiencies in the Loss of Coolant Accident Analysis.