05000321/LER-2010-005, Unit 1 Regarding Inability of Redundant Main Control Room Air Conditioner to Auto-Start for Pressurization Mode
| ML102740274 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 09/30/2010 |
| From: | Madison D Southern Nuclear Operating Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| NL-10-1910 LER 10-005-00 | |
| Download: ML102740274 (6) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 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 |
| 3212010005R00 - NRC Website | |
text
Dennis R. Madison Vice President - Hatch September 30, 2010 Southern Nuclear Operating Company. Inc.
Plant Edwin I Hatch 11028 Hatch Parkway North Baxley. Georgia 31513 Tel 912.537.5859 Fax 912366.2077 SOUTHERNA COMPANY Docket Nos.:
50-321; 50-366 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 NL-10-1910 Edwin I. Hatch Nuclear Plant Licensee Event Report Inability of Redundant Main Control Room Air Conditioner to Auto-Start for Pressurization Mode Ladies and Gentlemen:
In accordance with the requirements of 10 CFR 50.73(a)(2)(i)(B), Southern Nuclear Operating Company is submitting the enclosed Licensee Event Report (LER) concerning the inability of redundant main control room air conditioner to auto-start for pressurization mode.
This letter contains no NRC commitments. If you have any questions, please contact Steven Tipps at (912) 537-5880.
Respectfully submitted,
~~YYJ~.I D. R. Madison Vice President - Hatch DRM/sbt Enclosures: LER 1-2010-005 cc:
Southern Nuclear Operating Company Mr. J. T. Gasser, Executive Vice President Ms. P. M. Marino, Vice President - Engineering RTYPE: CHA02.004 U. S. Nuclear Regulatory Commission Mr. L. A. Reyes, Regional Administrator Mr. R. E. Martin, NRR Project Manager - Hatch Mr. E. D. Morris, Senior Resident Inspector - Hatch Mr. P. G. Boyle, NRR Project Manager
NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 08/31/2010 (9-2007)
, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.
- 13. PAGE Edwin I. Hatch Nuclear Plant - Unit 1 05000-321 1
of 5
- 4. TITLE Inability of Redundant Main Control Room Air Conditioner to Auto-Start for Pressurization Mode
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED SEQUENTIAL REV FACILl1Y NAME DOCKET NUMBER MONTH DAY YEAR YEAR NUMBER NO.
MONTH DAY YEAR Edwin I. Hatch NP - Unit 2 05000-366 FACILl1Y NAME DOCKET NUMBER 08 03 2010 2010 - 005 - 00 09 30 2010 05000
- 9. OPERAllNG MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR§:
(Check all that apply) o 20.2201 (b) o 20.2203(a)(3)(i) o 50.73(a)(2)(i)(C) 0 50.73(a)(2)(vii) 1 o 20.2201 (d) o 20.2203(a)(3)(ii) o 50.73(a)(2)(ii)(A) 0 50.73(a)(2)(viii)(A) o 20.2203(a)(1) o 20.2203(a)(4) o 50.73(a)(2)(ii)(B) 0 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) 0 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) 0 50.73(a)(2)(x) o 20.2203(a)(2)(iii) o 50.36(c)(2) o 50.73(a)(2)(v)(A) 0 73.71 (a)(4) 99.8 %
o 20.2203(a)(2)(iv) o 50.46(a)(3)(ii) o 50.73(a)(2)(v)(B) 0 73.71(a)(5) o 20.2203(a)(2)(v) o 50.73(a)(2)(i)(A) o 50.73(a)(2)(v)(C) 0 OTHER o 20.2203(a)(2)(vi) 181 50.73(a)(2)(i)(B) o 50.73(a)(2)(v)(D)
Specify in Abstract below or in (If more space is required, use additional copies of (If more space is required, use additional copies of NRC Form 366A) (17) accomplished. If the 'A' AHU failed for whatever reason, the 'B' AHU would have automatically started and tripped thereby affecting the redundancy of this function. Operations procedures would have had the operator check LO see if the 'B' AHU had started and if it was not running would be manually restarted or the 'C' AHU would be placed into service in response to the alarmed condition caused by low differential pressure between the control room and the turbine deck. The 'B' or 'C' AHU would then operate, restore the required differential pressure and continue to operate for the required mission time of 30 days.
Despite the "as found" condition involving the excessive temperature of the cooling water for AHUs that are either in the "off' or "standby" position, the 'B' AHU could be manually restarted by resetting the high pressure cutout switch. Since most of the hot leg of water would have been flushed through the AHU during the initial start prior to its trip, the AHU could be manually re-started and run normally for its required mission time of 30 days. Since the MCR air conditioners are manually placed into service, the capability for control room cooling was retained prior to discovery of this condition and improved provision was made for it following its discovery.
The MCREC system would function as required to pressurize the main control room and upon loss of the 'A' AHU would not be able to automatically pressurize the control room boundary. However, as previously described operator actions required by procedure would be taken to restore the 'B' or start the 'C' AHU.
The ability to manually start the needed MCR air conditioner was retained during this event. No design basis accident (DBA) event condition occurred prior to the discovery of this condition that would have required automatic initiation of the MCREC system to function in the pressurization mode.
Based on this information the this discovered condition is considered to have low safety significance, since the required specified safety functions would have occurred as required or restored in a relatively short time frame.
CORRECTIVE ACTIONS
The corrective actions taken included: replacing the inlet cooling water piping for the 'B' AHU 1Z41-B008B, calibrating the pressure switch that performs a trip function on high head pressure and inspecting valve IP41-F1247. Additionally, an Operating Order was developed and procedures revised to address the manual actions for restarting a chiller follOWing a trip of the nature addressed in this LER. Also, operating limitations were established to ensure that the AHU's are operated in a configuration to ensure compliance with the Technical Specifications. Planned corrective actions include completing an engineering review to determine design operating limitations for starting a chiller in high ambient conditions and from that evaluation develop and implement a design change as required to resolve this problem.
ADDITIONAL INFORMATION
SIMILAR EVENTS:
LER 1-2009-006, "Main Control Room Air Conditioner Due to Inoperable Solenoid Valve," identified a condition involving failed solenoid valves in the PSW cooling lines going to a non-safety related air conditioner. The failed solenoid valves would not isolate this non-safety related line which would upon failure in a design basis accident route some of the cooling water needed for the MCR air conditioning system for anPRINTED ON RECYCLED PAPER)(9-2007)
LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET U.S. NUCLEAR REGULATORY COMMISSION 2010 005 00
- 1. FACILITY NAME Edwin I. Hatch Nuclear Plant - Unit 1
- 2. DOCKET 05000321 YEAR
- 6. LER NUMBER I
SEQUENTIAL I REVISION NUMBER NUMBER 5
- 3. PAGE of 5
NARRAllVE (If more space is required, use additional copies of NRC Form 366A) (17) air conditioner aligned to Unit I PSW supply. An Engineering analysis was performed that demonstrated that there would not be a loss of function in the event that such a condition occurred. The line was isolated which restored the normal flow to the MCR air conditioner. The resulting corrective actions were not associated with the ability of a MCR AHU starting and running and are not relevant to the condition being reported in this LER.
LER 1-20 I0-002, "Degraded Plant Service Water Cooling to Main Control Room Air Conditioner Results in Loss of Function" identified a condition involving the degradation of cooling water lines to the MCR air conditioners. The degraded condition of the PSW cooling to the MCR air conditioners was similar in nature to the condition of the inlet cooling water line to the 'B' AHU reported in the current LER. The corrective actions from the previous LER involved cleaning of a portion of associated piping, but cleaning of the inlet line for the 'B' AHU was not performed at that time. Due to the "as found" condition of the cooling water line going to the 'B' AHU, cleaning of the line would not have precluded the condition, since the impact the temperature of the stagnant water would have on the operation of the 'B' AHU was not known before running the system in its current configuration to take operating data.
NRC FORM 36M (9-2007)
PRINTED ON RECYCLED PAPER)