05000456/LER-2010-006, For Braidwood Station, Unit 1 Regarding Technical Specifications Allowed Outage Time Extension Request for Component Cooling System Contained Inaccurate Design Information That Significantly Impacted the Technical Justification

For Braidwood Station, Unit 1 Regarding Technical Specifications Allowed Outage Time Extension Request for Component Cooling System Contained Inaccurate Design Information That Significantly Impacted the Technical Justification

ML110120143
Person / Time
Site:	Braidwood   (NPF-072, NPF-077)
Issue date:	01/11/2011
From:	Shahkarami A Exelon Nuclear, Exelon Generation Co
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
BW110002 LER 10-006-00
Download: ML110120143 (5)

LER-2010-006, For Braidwood Station, Unit 1 Regarding Technical Specifications Allowed Outage Time Extension Request for Component Cooling System Contained Inaccurate Design Information That Significantly Impacted the Technical Justification

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
4562010006R00 - NRC Website

text

10 CFR 50.73 January 11, 2011 BW110002 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Braidwood Station, Units 1 and 2 Facility Operating license Nos. NPF-72 and NPF-77 NRC Docket Nos. STN 50-456 and STN 50-457 Subject: Licensee Event Report 2010-006 Technical Specifications Allowed Outage Time Extension Request for Component Cooling System Contained Inaccurate Design 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," paragraph (a)(2)(ii)(B), as an unanalyzed condition that significantly degraded plant safety, and paragraph (a)(2)(v)(B) as a condition that could have prevented the fulfillment of a system's safety function. On November 12, 2010, it was identified that the Technical Specifications Allowed Outage Time extension request for the Component Cooling system contained inaccurate design information that significantly impacted the technical justification. 10 CFR 50.73(a) requires an LER to be submitted within 60 days following discovery of the event. Therefore, this report is being submitted by January 11, 2011.

There are no regulatory commitments contained in this letter. Should you have any questions concerning this submittal, please contact Mr. Ronald Gaston, Regulatory Assurance Manager, at (815) 417-2800.

Respectfully, Amir Shahkarami Site Vice President Braidwood Station

Enclosure:

LER 2010-006-00 cc: NRR Project Manager - Braidwood Station Illinois Emergency Management Agency - Division of Nuclear Safety US NRC Regional Administrator, Region III US NRC Senior Resident Inspector (Braidwood Station)

Illinois Emergency Management Agency - Braidwood Rep

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 (10-2010)

, the NRC may digits/characters for each block) not conduct or sponsor, and a person is not required to respond to, the information collection.

13. PAGE Braidwood Station, Unit 1 05000456 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 YEAR 'SEQUENTIAL' REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR NUMBER NO.

MONTH DAY YEAR Braidwood Station Unit 2 05000457 FACILITY NAME DOCKET NUMBER 11 12 2010 2010 - 006 - 00 01 11 2011 N/A N/A

9. OPERATING MODE

11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 1 o 20.2201(b) o 20.2203(a)(3)(i) o 50.73(a)(2)(i)(C) o 50.73(a)(2)(vii) o 20.2201(d) o 20.2203(a)(3)(ii) o 50.73(a)(2)(ii)(A) o 50.73(a)(2)(viii)(A) o 20.2203(a)(1) o 20.2203(a)(4)

[2J 50.73(a)(2)(ii)(B) o 50.73(a)(2)(viii)(B) o 20.2203(a)(2)(i) o 50.36(c)(1 )(i)(A) o 50.73(a)(2)(iii) o 50.73(a)(2)(ix)(A)

10. POWER LEVEL o 20.2203(a)(2)(ii) o 50.36(c)(1)(ii)(A) o 50.73(a)(2)(iv)(A) o 50.73(a)(2)(x) o 20.2203(a)(2)(iii) 50.36(c)(2) o 50.73(a)(2)(v)(A) o 73.71(a)(4) 100 o 20.2203(a)(2)(iv) o 50.46(a)(3)(ii)

[2J 50.73(a)(2)(v)(B) o 73.71(a)(5) o 20.2203(a)(2)(v) o 50.73(a)(2)(i)(A) o 50.73(a)(2)(v)(C) o OTHER o 20.2203(a)(2)(vi) o 50.73(a)(2)(i)(B) o 50.73(a)(2)(v)(D)

Specify in Abstract below or in In addition, another potentially significant discrepancy was discovered in both the CC and RH system analyses, in that it did not correctly account for the operational requirement to preemptively split CC trains in a post accident scenario.

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 (EGG) concluded that it would have been significant enough to impact the NRC's approval of the LAR and that the AOT 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 AOT 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 AOT 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 UO CC pump shall not be used to satisfy the requirements of the 1B or 2B CC pump.

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 system's safety function.

C.

Cause of Event

The most probable causes of the event are limited procedural guidance for preparing correspondence, and ambiguity in intended system operation. The root cause of the inaccurate LAR in the 1987 timeframe was indeterminate due to the timeframe when the event occurred. The processes in place for preparing and reviewing LARs in the 1987 timeframe were not as robust as the current processes.

D.

Safetv Consequences:

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 unit's 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 three year historical review of times the common CC system pump replaced either unit's B train pump while in the mode of applicability resulted in finding two instances for Unit 1 and two for Unit 2. The duration time frames were 80 and 138 hours0.0016 days <br />0.0383 hours <br />2.281746e-4 weeks <br />5.2509e-5 months <br /> for Unit 1, and 59 and 281 hours0.00325 days <br />0.0781 hours <br />4.646164e-4 weeks <br />1.069205e-4 months <br /> for Unit 2.

~.

Corrective Actions

The corrective actions include:

Investigate modification of the CC system 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.

Previous Occurrences

There have been no previous, similar Licensee Event Reports identified at the Braidwood Station.

G.

Component Failure Data

Manufacturer N/A Nomenclature N/A Model N/A Mfg. Part Number N/A