ENS 43990
ENS Event | |
|---|---|
00:02 Feb 16, 2008 | |
| Title | Potential Inoperability of Emergency Core Cooling Systems Due to an Unalalyzed Condition |
| Event Description | This notification is being made in accordance with 10 CFR 50.72(b)(3)(ii) which states in part Any event or condition that results in (A) the condition of the nuclear power plant, including its principle safety barriers, being seriously degraded; or (B) the nuclear power plant being in an unanalyzed condition that significantly degrades plant safety and 10 CFR 50.72(b)(3)(v) which states in part Any event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to: (A) Shut down the reactor and maintain it in a safe shutdown condition; (B) Remove residual heat; (C) Control the release of radioactive material; or (D) Mitigate the consequences of an accident. This notification describes a licensee identification of a condition where the low pressure emergency core cooling systems (ECCS) may not have been able to perform their safety functions of removing residual heat and significantly degrades plant safety. The condition has been corrected.
At 2152 on 15 February 2008, while operating at 100% power, Nine Mile Point Unit 2 completed evaluating a 10 CFR 21 communication from General Electric on ECCS suction strainers, and concluded that the calculation on debris head loss was non conservative. The original design basis net positive suction head calculations assumed a suppression pool water level of 199.5 feet. Based upon the General Electric notification, at this suppression pool water level, the low pressure core spray and all three residual heat removal systems might not have been able to perform their safety functions. Further engineering evaluation determined that if the suppression pool level was [greater than or equal to] 200.3 feet then the suction strainers debris head loss could be met and the low pressure ECCS would be able to perform their safety functions. At 1902 the control room operators took action to raise suppression pool water level while engineering completed their evaluation based on the expectation that suppression pool water would have to be raised. At 1910 on 15 February 2008, suppression pool water level was raised to 200.3 feet, which resulted in the low pressure core spray and residual heat removal systems being able to perform their safety function. The licensee will notify the NRC Resident Inspector.
After further review, this event notification report is being retracted based on the following: The notification was initiated due to a 10 CFR 21 communication from General Electric on ECCS suction strainers, indicating that the calculation of suction strainer head loss was non-conservative. As a result, at the assumed suppression pool water level of 199.5 feet, adequate net positive suction head may not be available for the low-pressure ECCS pumps. Suppression pool water level was raised 9.8 inches, to 200.3 feet, which provided assurance that the low pressure ECCS pumps were capable of performing their specified safety functions. Further evaluation by plant staff has determined that there are margins available in the suction strainer head loss calculations and in the design basis ECCS pump net positive suction head calculations that, when combined, exceed the increase in suction strainer debris head loss identified in the General Electric communication. Based on these available margins, there was adequate net positive suction head for the low pressure ECCS pumps at the originally assumed suppression pool water level of 199.5 feet. In addition, the as-found quantity of corrosion products and debris removed from the suppression pool during the current refueling outage was significantly less than the quantity assumed in the design basis suction strainer head loss calculations, indicating that additional analytical margin existed. Thus, the low pressure ECCS pumps were operable and capable of performing their specified safety functions without reliance on the 9.8 inches of water level added to the Suppression pool. Raising the suppression pool water level was a conservative action but was not necessary to maintain operability of the low pressure ECCS pumps. Therefore, this event is not reportable under either 10 CFR 50.72(b)(3)(ii) or 10 CFR 50.72(b)(3)(v). The licensee notified the NRC Resident Inspector. R1DO (Conte) notified. |
| Where | |
|---|---|
Nine Mile Point  New York (NRC Region 1) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat | |
| Time - Person (Reporting Time:+2.72 h0.113 days <br />0.0162 weeks <br />0.00373 months <br />) | |
| Opened: | Chris Skinner 02:45 Feb 16, 2008 |
| NRC Officer: | Jason Kozal |
| Last Updated: | Apr 12, 2008 |
| 43990 - NRC Website
Loading map... | |
Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
Nine Mile Point with 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
WEEKMONTHYEARENS 554922021-09-25T07:42:00025 September 2021 07:42:00
[Table view]10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat Loss of Uninterruptible Power Supply Resulted in Isolation of Two Emergency Condensers ENS 521332016-07-29T03:57:00029 July 2016 03:57:00 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat Temporary Loss of Power to the Emergency Condenser ENS 500982014-05-08T20:45:0008 May 2014 20:45:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Postulated Hot Short Fire Event That Could Adversely Impact Safe Shutdown Equipment ENS 494642013-10-22T18:00:00022 October 2013 18:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Postulated Hot Short Fire Event That Could Adversely Impact Safe Shutdown Equipment ENS 468272011-05-06T17:00:0006 May 2011 17:00:00 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Changes in Fuel Vendor Calculation Methodology to Comply with the Eccs Performance Requirements of 10 Cfr 50.46(B) ENS 439902008-02-16T00:02:00016 February 2008 00:02:00 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Potential Inoperability of Emergency Core Cooling Systems Due to an Unalalyzed Condition ENS 407492004-05-14T13:17:00014 May 2004 13:17:00 Other Unspec Reqmnt, 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition Change in the Methodology Used by Ge/Gnf to Demonstrate Compliance with Eccs Performance Requirements 2021-09-25T07:42:00 | |