05000361/LER-2007-002
| San Onofre Nuclear Generating Station (Songs) Unit 2 | |
| Event date: | 6-21-2007 |
|---|---|
| Report date: | 08-17-2007 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3612007002R00 - NRC Website | |
Discovery Date: June 21, 2007 Reactor Vendor: Combustion Engineering Mode: Mode 1 — Power Operation Power: 96 percent
Description of Event:
Technical Specification (TS) 3.3.13, Source Range Monitoring Channels, requires two channels of source range monitoring to be operable. This specification is applicable whenever the plant is in Modes 3, 4, and 5, with the reactor trip breakers open or control element assembly drive system not capable of CEA withdrawal. When applicable and with one source range monitor inoperable, plant operators are required to, in part, perform a Shutdown Margin (SDM) verification in accordance with Surveillance Requirement (SR) 3.1.1.2, if T(ave) is greater than 200 degrees F, or in accordance with SR 3.1.2.1, if T(ave) is less than 200 degrees F. Required Action A.2 of TS 3.3.13 has a required completion time of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> after entering an applicable plant condition and once every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> thereafter.
On June 20, 2007, Unit 2 was operating in Mode 1 at about 96 percent power. At about 1030 PDT, one channel of source range monitoring did not pass its surveillance requirements and was declared inoperable. Consistent with plant procedures, Operators placed a Limiting Condition for Operation Action Requirements/Equipment Deficiency Mode Restraint (LCOAR/EDMR) tag next to the channel indicator (the channel indicator continued to function).
On June 20, 2007, at about 2240 PDT, Unit 2 was operating in Mode 1 at about 96 percent power when a line in the instrument air system separated at a soldered connection joint. Operators manually tripped the unit at about 2250 PDT, June 20, 2007. The details of that event are provided in LER 2007-001.
When operators manually tripped the reactor, the plant entered Mode 3 and entered the applicability of TS 3.3.13. When completing the post trip actions required by Emergency Operating Instructions (EOI), a control room operator failed to notice that one channel of source range monitoring channels was out of service and failed to complete the SDM verification by 0250 PDT, June 21, 2007, as required by TS 3.3.13, Action A.2. Southern California Edison is reporting this occurrence to the NRC in accordance with 10CFR50.73(a)(2)(i)(B).
Cause of Event:
The cause of the event was individual operator error. The Reactor Operator (RO) failed to correctly respond to the LCOAR/EDMR tag posted next to the Startup Channel indicator. When the RO performed the channel check required by procedure, he observed both channels indicating and did not question their operability.
Corrective Actions:
The Operator involved in this case has been coached on the requirement to check for LCOAR/EDMR tags when determining whether TS related components are functional. SCE also reviewed this event with all other Licensed Operators.
2007 --002 00 Additional corrective actions will be implemented if they are identified.
Safety Significance:
There was no safety significance to this event. At about 0830 PDT on June 21, 2007, plant operators completed the required SDM verification and confirmed the SDM satisfied the requirements of SR 3.1.1.2 [T(ave) was greater than 200 degrees F.]
Additional Information:
In the last three years, there have been no other reported occurrences of a missed TS required surveillance caused by failing to notice that TS required equipment was out of service.