05000454/LER-2010-001, Regarding Technical Specifications Allowed Outage Time Extension Request for Component Cooling System Contained Inaccurate Design Information That Significantly Impacted the Technical Justification
| ML110110654 | |
| Person / Time | |
|---|---|
| Site: | Byron  |
| Issue date: | 01/11/2011 |
| From: | Enright D Exelon Generation Co, Exelon Nuclear |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 2011-0013 LER 10-001-00 | |
| Download: ML110110654 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 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)(ii)(B), Unanalyzed Condition 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 |
| 4542010001R00 - NRC Website | |
text
Exel n.
Nuclear 10 CFR 50.73 January11, 2011 Byron Ltr: 2011-0013 File:
1.10.0101 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Byron Station, Unit 1 and 2 Facility Operating License Nos. NPF-37 and NPF-66 NRC Docket Nos. STN 50-454 and STN 50-455
Subject:
Licensee Event Report 2010-001-00, Technical Specification Allowed Outage Time Extension Request for Component Cooling Water System, Contained Inaccurate Information That Significantly Impacted The Technical Justification The enclosed Licensee Event Report (LER) is being submitted in accordance with 10 CFR 50.73, Licensee event report system. The LER involves a 1987 license amendment request that unknowingly contained inaccurate information.
There are no regulatory commitments contained in this letter. Should you have any questions concerning this submittal, please contact Mr. David Gudger, Regulatory Assurance Manager, at (815) 406-2800.
Respectfully, Daniel J. Enright
\\,
Site Vice President Byron Station DJ E/DTG/cy
Enclosure:
LER Number 2010-001-00
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB: NO. 3150-0104 EXPIRES: 10/31/2013 (10-20101
, the NRC may not conduct or sponsor, and a person is not required to respond to, the digits/characters for each block) information collection.
- 13. PAGE Byron Station, Unit 1 05000454 1
OF 4
- 4. TITLE Technical Specifications Allowed Outage Time Extension Request for Component Cooling System Contained Inaccurate Design Information That Significantly Impacted the Technical Justification
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OThER FACILITIES INVOLVED FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR SEJJjlAL E 0
V MONTH DAY YEAR Byron Station, Unit 2 05000455 FACILITY NAME DOCKET NUMBER 11 12 2010 2010 001 00 01 11 2011
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMI1ThD PURSbANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
Q 20.2201(b)
Q 20.2203(a)(3)(i)
Q 50.73(a)(2)(i)(C)
Q 50.73(a)(2)(vii) 1 Q 20.2201(d)
Q 20.2203(a)(3)(ii)
Q 50.73(a)(2)(ii)(A)
Q 50.73(a)(2)(viii)(A)
Q 20.2203(a)(1)
Q 20.2203(a)(4) 50.73(a)(2)(ii)(B)
Q 50.73(a)(2)(viii)(B)
D 20.2203(a)(2)(i)
Q 50.36(c)(l)(i)(A)
Q 50.73(a)(2)(iii)
Q 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL Q 20.2203(a)(2)(ii)
Q 50.36(c)(1)(ii)(A)
Q 50.73(a)(2)(iv)(A)
Q 50.73(a)(2)(x)
Q 20.2203(a)(2)(iii)
Q 50.36(c)(2)
Q 50.73(a)(2)(v)(A)
Q 73.71 (a)(4) 100 20.2203(a)(2)(iv)
Q 50.46(a)(3)(ii) 50.73(a)(2)(v)(B)
Q 73.71 (a)(5)
Q 20.2203(a)(2)(v)
Q 50.73(a)(2)(i)(A)
U 50.73(a)(2)(v)(C)
U OTHER U 20.2203(a)(2)(vi)
U 50.73(a)(2)(i)(B)
U 50.73(a)(2)(v)(D)
Specify in Abstract below or in Re-creation of the 1984 vintage PRA modeling and analysis was not feasible in order to determine a quantitative value to this discrepancy. Therefore, it is unknown whether this negative impact would have been significant enough to have impacted NRC approval of the LAR for CC and RH. However, Exelon Generation Company, LLC (EGC) concluded that it would have been significant enough to impact the NRCs approval of the LAR and that the ACT for TS 3.7.7, Component Cooling, and TS 3.5.3, ECCS-Operating (RH Sub-system) should be considered non-conservative and the provisions of NRC Administrative Letter 98-10, Dispositioning of Technical Specifications That Are Insufficient to Assure Plant Safety, be invoked.
The following administrative controls have been implemented at Byron and Braidwood Stations pending modifications to address the CC design discrepancies:
The ACT for TS 3.7.7, Component Cooling Condition B for one required CC pump inoperable has been restricted to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> The ACT for TS 3.5.2, ECCS-Operating Condition A has been restricted to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> for an inoperable RH train The U0 CC pump has been restricted from being aligned to either Units B CC train This condition is reportable to the NRC pursuant to 10 CFR 50.73(a)(2)(ii)(B) as an unanalyzed condition that significantly degraded plant safety and 10 CFR 50.73(a)(2)(v)(B) as a condition that could have prevented the fulfillment of a systems safety function.
C.
Cause/s of the Event A root cause evaluation concluded the cause of the inaccurate LAR in the 1987 timeframe was indeterminate due to the time frame when the event occurred. The most probable causes are limited procedural guidance for preparing correspondence and ambiguity in intended system operation. The processes in place for preparing and reviewing LARs in the 1987 timeframe were not as robust as the current processes.
The root cause evaluation also identified the potential missed opportunities that occurred between 1987 and present to recognize and correct the TS implications of the design discrepancies with the common CC system pump. Seven missed opportunities were identified with causes attributed to a lack of technical rigor, lack of technical knowledge and understanding of the system, and lack of questioning attitude.
D.
Safety Significance
The design basis safety function of the CC system is to remove the post LOCA heat load from the containment sump during the ECCS recirculation phase. The containment sump is the suction source for the ECCS pumps during the recirculation phase.
There were no actual safety consequences resulting from this condition. No actual loss of a safety function occurred. However, the potential existed for more severe conditions to have developed, when the common CC system pump was aligned to replace either units B CC train pump and CC trains split. With the postulation of design basis assumptions, a loss of the CC safety function could have occurred and, if not mitigated, would in turn lead to a loss of the ECCS.
A 3-year historical review of times the common CC system pump replaced either units B train pump resulted in finding three instances for Unit 1 and two for Unit 2. The duration time frames ranged from 13 to 87 hours0.00101 days <br />0.0242 hours <br />1.438492e-4 weeks <br />3.31035e-5 months <br /> for Unit 1 and 15 to 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> for Unit 2.
E.
Corrective Actions
The CC system will be modified to eliminate the design discrepancies with the common CC pump and the need to pre-emptively split CC trains.
A review of the current LAR preparation and review process concluded it is sufficiently robust to minimize potential inaccurate information from not being identified.
Training will be conducted to appropriate Site personnel to raise awareness of the circumstances and missed opportunities for recognizing the significance and implications of the design discrepancies.
An extent of condition review will be conducted.
F.
Previous Occurrences
No previous occurrences were identified.
G.
Corn Donent Failure Data:
Manufacturer Nomenclature Model Mfg. Part Number N/A N/A N/A N/A