05000311/LER-2001-002
| Salem Unit 2 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3112001002R00 - NRC Website | |
PLANT AND SYSTEM IDENTIFICATION
Westinghouse - Pressurized Water Reactor Containment Spray System / Spray Additive Tank {BE/TK}* * Energy Industry Identification System (EIIS) codes and component function identifier codes appear in the text as {SS/CCC}.
IDENTIFICATION OF OCCURRENCE
Event Date: This event was discovered on June 6, 2001
CONDITIONS PRIOR TO OCCURRENCE
Mode 1 — 100%
DESCRIPTION OF OCCURRENCE
On May 7, 2001 at 1505 during the scheduled performance of the Technical Specification (TS) Surveillance 4.6.2.2.b.2, Chemistry personnel noted that the Containment Spray (CS) System Spray Additive Tank (SAT) {BE/TK} Sodium Hydroxide (NaOH) concentration was below the minimum TS required concentration of 30 percent by weight (% w/w). With the NaOH concentration below the required acceptance criteria, TS 3.6.2.2 was entered. TS 3.6.2.2 requires that within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> the concentration be restored to within the acceptable limits or the unit 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 />. Actions to restore the NaOH concentration were completed and the Tech Spec LCO 3.6.2.2 was exited at 2230 hours0.0258 days <br />0.619 hours <br />0.00369 weeks <br />8.48515e-4 months <br /> on May 8, 2001. An evaluation to determine the apparent cause for the NaOH concentration being outside Technical Specification limits was initiated. On June 6, 2001 the evaluation determined that based on concentration change between two routine samples of the Unit 2 CS SAT collected on November 21, 2000 and May 7, 2001, and the leakage rate identified through the tank parallel isolation valves 2CS16 and 17, the tank was below the lower concentration limit for up to a maximum of 109 days prior to the May 7, 2001 discovery.
A review of this event determined that a Safety System Functional Failure (SSFF) as defined in NEI 99-02 did not occur. No structures, systems or components were inoperable at the time of this event that contributed to this event.
CAUSE OF OCCURRENCE
There were two apparent causes of the SAT dilution.
1) One or both of the parallel CS SAT motor operated isolation valve(s) 2CS 16 and 17 leaking (The gravity head from the RWST caused leakage into the Containment Spray Additive tank), and 2) The failure of plant operating personnel to a) trend the long term gradual rise in SAT volume that would have identified the leaking isolation valve (in a timely fashion), and b) take the appropriate action to prevent operating with a SAT sodium hydroxide concentration below TS limits.
PRIOR SIMILAR OCCURRENCES
Prior Salem Units 1 and 2, and Hope Creek LERs, from 1998 through 2001, were reviewed. No events, similar to this one, that resulted directly from inadequate trending of plant operational data were identified.
SAFETY CONSEQUENCES AND IMPLICATIONS
There were no actual safety consequences associated with this event. The TS requires that the CS SAT NaOH concentration be maintained between 30 and 32 % w/w. Although the concentration was found to be at 28.4 % w/w, an analysis (performed in 1988 by the NSSS Vendor) concluded that with a concentration as low as 28 % w/w the system was capable of meeting all required design functions in the event of a Large Break Loss of Cooling Accident (LB LOCA). The consequences of a reduced NaOH concentration (28.4 % w/w) would have had no impact on the radiological consequences of an accident.
The SAT, as a part of the CS system, remained capable of performing its safety function following a loss of offsite power coincident with a design basis LOCA.
Based on the above, this event did not affect the health and safety of the public.
CORRECTIVE ACTIONS
1. The Containment Spray System Spray Additive Tank sodium hydroxide concentration was restored to Technical Specification value within the LCO allowed time (72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />).
2. Chemistry has initiated additional trending of the SAT level. Limits have been established in the chemistry data management system to identify when tank concentration has been diluted to 30.5 w/w based on level increases. This will allow actions to be taken prior to the tank concentration going outside the Technical Specification band.
3. Corrective Maintenance Notifications (20068333 and 20068334) were initiated to inspect/repair spray additive tank isolation valves to stop in-leakage. Until repairs are accomplished, Spray additive tank level will be tracked and trended to ensure Tech Spec compliance. Note: SAT level and Sodium Hydroxide concentration were adjusted on July 10, 2001.
4. To prevent recurrence, a Corrective Action Notification (20073445) has been initiated to evaluate the current tank level control bands for the SAT.
COMMITMENTS
The corrective actions cited in this LER are voluntary enhancements and do not constitute commitments.
TO: � Harry Keiser FROM: � D. F. Garchow 0. -Li SUBJECT: LER #311/01-002-00, "Containment Spray Additive Tank Exceeded Technical Specification Limit Allowable Outage Time" DATE: � AUG 0 2 2001
Root Cause:
The apparent causes of the SAT dilution event were:
a) One or both of the parallel CS SAT motor operated isolation valve(s) 2CS 16 and 17 leaking. The gravity head from the RWST caused leakage into the Containment Spray Additive tank.
b) The failure of plant operating personnel to 1) trend the long term gradual rise in SAT volume that would have identified the leaking isolation valve (in a timely fashion), and 2) take the appropriate action to prevent operating with a SAT sodium hydroxide concentration below TS limits.
Corrective Actions:
1. The Containment Spray System Spray Additive Tank sodium hydroxide concentration was restored to Technical Specification value within the LCO allowed time (72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />).
2. Chemistry has initiated additional trending of the SAT level. Limits have been established in the chemistry data management system to identify when tank concentration has been diluted to 30.5 w/w based on level increases. This will allow actions to be taken prior to the tank concentration going outside the Technical Specification band.
3. Corrective Maintenance Notifications (20068333 and 20068334) were initiated to inspect/repair spray additive tank isolation valves to stop in-leakage. Until repairs are accomplished, Spray additive tank level will be tracked and trended to ensure Tech Spec compliance. Note: SAT level and Sodium Hydroxide concentration were adjusted on July 10, 2001.
4. To prevent recurrence, a Corrective Action Notification (20073445) has been initiated to evaluate the current tank level control bands for the SAT.
Commitments:
No commitments are made in this LER.
CC
Ken Moore