05000315/LER-2006-001, Regarding Plant Shutdown Required by Technical Specification Action 3.6.5.B.1
| ML062780197 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 09/27/2006 |
| From: | Weber L Indiana Michigan Power Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| AEP-NRC-2573-34 LER 06-001-00 | |
| Download: ML062780197 (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 |
| 3152006001R00 - NRC Website | |
text
Indiana Michigan Power INDIANA Cook Nuclear Plant MICHIGAN One Cook Place ViAER Bridgman, MI 49106 AEP.com A unit of American Electric Power September 27, 2006 AEP:NRC:2573-34 10 CFR 50.73 10 CFR 50.4 Docket No. 50-315 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Mail Stop O-P1-17 Washington, DC 20555-0001 Donald C. Cook Nuclear Plant Unit 1 LICENSEE EVENT REPORT 315/2006-001-00 PLANT SHUTDOWN REQUIRED BY TECHNICAL SPECIFICATION ACTION 3.6.5.B.1 In accordance with the criteria established by 10 CFR 50.73 entitled Licensee Event Report System, the following report is being submitted:
LER 315/2006-001-00: 'Plant Shutdown Requir&d by Technical Specification Action 3.6.5.B.1" There are no commitments contained in this submittal.
Should you have any questions, please contact Ms. Susan D. Simpson, Regulatory Affairs Manager, at (269) 466-2428.
Sincerely, Lawrence J. Weber Plant Manager HLE/jen Attachment
U. S. Nuclear Regulatory Commission AEP:NRC:2573-34 Page 2 c:
J. L. Caldwell, NRC Region III K. D. Curry - AEP Ft. Wayne, w/o attachment INPO Records Center J. T. King, MPSC - w/o attachment MDEQ - WHMD/RPMWS - w/o attachment NRC Resident Inspector P. S. Tam, NRC Washington DC
NRC Fofim 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES 6/30/2007 (6-2004)
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 1. FACIUTY NAME
- 2. DOCKET NUMBER
- 3. PAGE Donald C. Cook Nuclear Plant Unit 1 05000-315 1 of 3
- 4. TITLE Plant Shutdown Required by Technical Specification Action 3.6.5.B.1
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACIUTIES INVOLVED SEQUENTIAL REVISION FACILITY NAME DOCKET NUMBER MONTH DAY YEAR YEAR NUMBER NUMBER MONTH DAY YEAR FACILITY NAME DOCKET NUMBER 07 30 2006 2006 001 00 09 27 2006
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)
[1 20.2201(b) 0 20.2203(a)(3)(i)
[I 50.73(a)(2)(i)(C)
[I 50.73(a)(2)(vii) 10 20.2201(d)
[I 20.2203(a)(3)(ii)
[0 50.73(a)(2)(ii)(A) 0l 50.73(a)(2)(viii)(A) o 20.2203(a)(1) 0 20.2203(a)(4) 0 50.73(a)(2)(ii)(B) 0 50.73(a)(2)(viii)(B) 0] 20.2203(a)(2)(i) 0 50.36(c)(1)(i)(A) 0 50.73(a)(2)(iii) 0 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL 0 20.2203(a)(2)(ii) 0 50.36(c)(1)(ii)(A) 0 50.73(a)(2)(iv)(A) 0 50.73(a)(2)(x) o 20.2203(a)(2)(iii)
[I 50.36(c)(2) 0 50.73(a)(2)(v)(A) 0] 73.71(a)(4) 100%
0 20.2203(a)(2)(iv) 0 50.46(a)(3)(ii) 0l 50.73(a)(2)(v)(B)
H73.71(a)(5) o 20.2203(a)(2)(v) 0 50.73(a)(2)(i)(A) 0 50.73(a)(2)(v)(C)
OTHER Specify in Abstract below
[] 20.2203(a)(2)(vi) 0 50.73(a)(2)(i)(B) 0 50.73(a)(2)(v)(D) or in (If more space is required, use additional copies of NRC Form (366A)
Conditions Prior to Event
Unit 1 in Mode 1 at 100% power.
Description of Event
As a result of an NRC inspection finding, Indiana Michigan Power Company (I&M) had approved a revised methodology for calculating lower containment average air temperature on July 28, 2006. The new methodology calculated an average lower containment temperature that was higher than the previous method.
While unrelated to the revised methodology for calculating lower containment average temperature, in July 2006, Unit 1 lower containment high temperature alarms were being evaluated by Engineering personnel and troubleshooting efforts were not able to increase Non-Essential Service Water (NESW) cooling flow through the Containment Lower Ventilation Units (CLVs). A temporary modification (T-Mod) to add supplemental cooled water to the NESW header as it entered containment was developed; however, delays in completing the design and implementation prevented it from being fully functional prior to the TS required shutdown.
The average temperature in the Unit 1 lower containment volume was determined to exceed 120 degrees Fahrenheit using the revised methodology and Unit 1 was declared to have exceeded the Limiting Condition for Operation of Technical Specification (TS) 3.6.5.b and Condition A was entered as of 2026 hours0.0234 days <br />0.563 hours <br />0.00335 weeks <br />7.70893e-4 months <br /> on July 29, 2006.
Required Action A.1 for Condition A was to restore containment average air temperature to within limits with an 8-hour completion time. At 0426 hours0.00493 days <br />0.118 hours <br />7.043651e-4 weeks <br />1.62093e-4 months <br /> on July 30, 2006, TS 3.6.5 Condition B was entered when the 8-hour completion time of Required Action A.1 for Condition A was not met. In accordance with normal plant operating procedures and TS 3.6.5, Condition B, Required Action B.1, Unit 1 was shut down and entered Mode 3 at 1014 hours0.0117 days <br />0.282 hours <br />0.00168 weeks <br />3.85827e-4 months <br /> on July 30, 2006.
Cause of Event
The causes of the Unit I shutdown were:
- 1. The containment cooling water system design did not support continued plant operation with sustained high cooling water (Lake Michigan) temperatures and potential for cooler fouling.
- 2. A failure by I&M Engineering personnel to recognize and communicate that an evaluation supporting past operability would not permit unit operation under some possible operating conditions during the summer (loss of operating margin). The failure to recognize this loss of operating margin resulted in a delay in communicating the impact of the lost margin to station management so compensatory actions could be developed at an earlier time.
Contributing causes were that actions that were initiated to reduce the average temperature were hindered because the CLVs were partially plugged with sediment and the supplemental cooling T-Mod installation had numerous delays that were not resolved in a timely manner.
Analysis of Event
During an NRC inspection in May 2006, the NRC inspectors identified a finding that the methodology for calculating lower containment average air temperature was non-conservative. A past operability calculation was completed in June 2006 using an appropriately conservative volume weighted methodology. This calculation showed that under recent worst case conditions, average temperature in lower containment did not exceed 119.7 (If more space is required, use additional copies of NRC Form (366A) degrees Fahrenheit with sustained lake temperatures of 79 degrees Fahrenheit in 2005, and thus a past operability concern was not present. The fact that containment temperatures may not remain below 120 degrees Fahrenheit when lake temperature exceeded 79 degrees Fahrenheit (permissible temperature was 85.8 degrees Fahrenheit) was not addressed.
In addition to the new average air temperature calculation methodology of lower containment, two of the four CLVs in Unit 1 had significant blockage that was identified prior to the 2006 summer season. Performance of on-line maintenance to clear the blockage in the CLVs prior to the 2006 summer season would have improved CLV performance.
A T-Mod to provide supplemental containment cooling was initiated two weeks prior to the TS required shutdown.
The effort to implement this T-Mod was significantly larger than originally understood. Numerous equipment problems were identified during the installation and testing of the T-Mod, and these problems either delayed its implementation or resulted in reduced performance of the T-Mod below what was expected.
This event had minimal nuclear safety impact on the plant. A Probabilistic Risk Assessment (PRA) was performed and determined there was no nuclear safety significance to this event. Unit 1 was shut down in a controlled fashion and manually tripped as part of the normal shutdown procedure at approximately 16.5 percent reactor power. All safety systems and plant equipment used in the shutdown functioned as designed. In that the shutdown was orderly, there was no significant probabilistic risk associated with this event.
Corrective Actions
Two of the four Unit 1 CLVs cooling coils were cleaned to remove sediment and debris.
The T-Mod for supplemental cooling was installed and used to reduce Unit 1 lower containment average air temperature to less than 120 degrees Fahrenheit.
Engineering procedures for calculations and modifications will be revised to provide explicit considerations related to identifying and managing operating and design margin.
The procedure for summer readiness will be revised to require installation of the supplemental containment cooling T-Mod during the summer months until such time that a design change is made that precludes the need for installation of the supplemental containment cooling T-Mod.
Analysis will be completed to determine when a CLV can be removed from service for cleaning, and maintenance activities to clean the CLVs will be generated when required.
Previous Similar Events
A review was conducted of station Condition Reports and LERs for the previous 3 years. No similar events were identified.