05000423/LER-2012-001
| Docket Numbersequential Revmonth Day Year Year Month Day Yearnumber No. 05000 | |
| Event date: | 02-09-2012 |
|---|---|
| Report date: | 04-03-2012 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications 10 CFR 50.73(a)(2)(v)(C), Loss of Safety Function - Release of Radioactive Material |
| LER closed by | |
| IR 05000245/2012003 (23 July 2012) | |
| 4232012001R00 - NRC Website | |
1. EVENT DESCRIPTION
(MPS3) discovered that all twelve main steam [AB] line pressure transmitter's (MSPT) Litton-Veam connectors had not been reconnected using new gaskets as required by Equipment Qualification (EQ) Record EQR 120-8-1 after maintenance was performed between January 17, 2012, and February 2, 2012. Upon discovery, operators declared the main steam line transmitters inoperable. This caused both channels of main steam line isolation (MSLI) to be declared inoperable. Technical Specification (TS) 3.3:2, Engineered Safety Features Actuation System Instrumentation, requires restoration of at least one channel of MSLI within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />, or be in hot standby within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, but does not specify actions to be taken when two channels are inoperable. Therefore, operators entered into TS Action Statement (TSAS) 3.0.3. By 2151 on February 9, 2012, new gaskets were installed in all twelve main steam line pressure transmitters, operators declared the transmitters operable, and exited MPS3 TSAS 3.0.3.
Because the actions were completed within the TS Action Statement, a plant downpower was not required. A loss of safety function for post accident monitoring purposes has been presumed because the EQ tests performed for the components in question did not mechanically cycle the Litton-Veam connectors. Therefore, by reusing the gasket, which has been mechanically cycled, the connector is no longer in the tested condition and is not considered qualified. The MSPTs also provide a post accident monitoring function per TS 3.3.3.6, Accident Monitoring Instrumentation. TS 3.3.3.6 requires that 2 channels of instrumentation must be restored within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />, or the unit must be placed in hot standby within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and hot shutdown within the following 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />. Since the condition was not recognized earlier, this also resulted in a condition prohibited by Technical Specifications (TS).
This condition is being reported pursuant to 10 CFR 50.73(a)(2)(v)(C) as an event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to shutdown the reactor and mitigate the consequences of an accident. This condition is also reportable as a condition prohibited by the plant's Technical Specifications pursuant to 10 CFR 50.73(a)(2)(i)(B).
2. CAUSE
The cause of this condition was determined to be a failure to incorporate 1998 EQ program requirement changes into the affected surveillance procedures as required by station administrative procedures.
3. ASSESSMENT OF SAFETY CONSEQUENCES
The main steam line steam generator (SG) [SG] pressure transmitters provide input to the MSLI signal that closes the fast acting main steam isolation valves (MSIVs) [V] located on each main steam line downstream of the four SGs. Sustained uncontrolled steam release from more than one SG is prevented following a postulated steam system piping failure (SLB) by the automatic trip of the MSIVs.
For a SLB inside containment, MSLI is activated by either high containment pressure or low steam line pressure, or manual operator action from the control room. For a SLB outside containment, manual operator action from the control room would be taken to isolate the SG if the SG pressure transmitters failed to automatically provide inputs for MSLI.
A loss of safety function for post accident monitoring of steam generator pressures has been presumed because the EQ tests performed for the components in question assumed the Litton-Veam connector seals are replaced each time after demating. There is a reasonable expectation that the MSPTs would have functioned to isolate the MSIVs on a steam line break in the main steam valve building.
Accordingly, it can reasonably be assured that the MSPTs would have functioned to support identifying and isolating a faulted steam generator due to either a steam line break or a feed line break in the main steam valve building. It cannot be assured that MSPTs would have provided their post accident monitoring function for the required mission time, i.e., 30 days; however, there are alternate indications which could have been used, including SG level, auxiliary feedwater flow and reactor coolant system temperature.
4. CORRECTIVE ACTION
New EQ gaskets were installed in all twelve main steam line pressure transmitters upon discovery. Also, Surveillance Procedure SP3444-B01 has been revised to incorporate a step to require changing out gaskets during future surveillance or maintenance evolutions. A review of similar surveillance procedures for MPS3 was performed, and no similar situations were found. Additional corrective actions are being taken in accordance with the station's corrective action program.
5. PREVIOUS OCCURRENCES
No previous similar events/conditions were identified.
Energy Industry Identification System (EllS) codes are identified in the text as [XX].