05000336/LER-2011-004
| Millstone Power Station - Unit 2 | |
| Event date: | 09-14-2011 |
|---|---|
| Report date: | 11-07-2011 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3362011004R00 - NRC Website | |
1. EVENT DESCRIPTION
On, September 14, 2011, with Millstone Power Station Unit 2 in Mode (MPS2) 1, at 100 % power, a historical condition was discovered (condition report (CR), CR442964) where a revision was required for surveillance procedure, SP 2401D, "RPS Matrix Logic and Trip Path Testing" to ensure compliance with Technical Specification (TS) 3.3.1.1 for MPS2.
During a start-up of MPS2, the Reactor Protection System (RPS) [JC] Matrix Logic and Trip Path Testing procedure specified the reactor trip circuit breakers (TCBs) [BKR] be closed (i.e., applying power to the control rod drive motors [AA] thus enabling the control element assemblies (CEAs) to be capable of being withdrawn). However, closing the TCBs (in order to perform the RPS Matrix Logic and Trip Path Testing) placed MPS2 in an applicable mode prior to having first completed a surveillance test demonstrating the TCBs were OPERABLE. This is contrary to the requirements of TS 4.0.4 which prohibits entry into an operational mode or other specified condition unless the surveillance requirement(s) have been performed within the stated interval.
A review of plant start-ups determined that at least once in the past 3 years, specifically during the start- up of MPS2 on July 24, 2009, the TCBs were closed rendering the CEA drive system capable of CEA withdrawal without first demonstrating the TCBs were operable.
This condition is being reported pursuant to 10 CFR 73(a)(2)(i)(B) as an operation or condition prohibited by TS.
2. CAUSE
The cause was determined to be an inadequate procedure review. TS Table 3.3-1 was changed in 2003 (amendment number 282) to add the TCBs (item number 15) to the table. During the implementation process for the 2003 TS change, when the surveillance procedure was revised, it was not recognized that the test method for performing the RPS Matrix Logic and Trip Path Testing resulted in closing the TCBs prior to documenting they were operable thus rendering the CEA drive system capable of CEA withdrawal (i.e., entering a specified mode).
3. ASSESSMENT OF SAFETY CONSEQUENCES
This condition was of very low safety significance. During the surveillance testing of the TCBs the CEAs remained fully inserted in the core, therefore no positive core reactivity change. Additionally, the performance of the RPS Matrix Logic and Trip Path Testing verified the operability of the TCBs. A review of the plant condition reporting system confirmed that there were no instances of inadvertent CEA motion noted.
4. CORRECTIVE ACTION
The surveillance procedure is being revised to specify an alternate method for testing the TCBs that does not result in rendering the CEA drive system capable of CEA withdrawal prior to closing the TCBs for performance of Matrix Logic and Trip Path testing. Additional corrective actions will be taken in accordance with the station's corrective action program.
5. PREVIOUS OCCURRENCES
No previous similar events/conditions were identified.
Energy Industry Identification System (EIIS) codes are identified in the text as [XX].