05000306/LER-2005-003

LER-2005-003,

Docket Number
Event date:
Report date:
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
3062005003R00 - NRC Website

EVENT DESCRIPTION

On February 11, 2005, NMC Staff identified leaks in the 22 and 23 containment fan coil units' (CFCUs). Since 22 CFCU is Train B containment cooling and 23 CFCU is Train A containment cooling, both trains of containment cooling were declared inoperable. Since Technical Specification (TS) 3.6.5 contains no condition for two trains of containment cooling inoperable, TS Limiting Condition for Operation (LCO) 3.0.3 was entered. NMC staff completed an evaluation that determined 21 CFCU (by itself) could perform the required safety function for Train A of containment cooling and declared Train A operable and exited LCO 3.0.3. 22 and 23 CFCUs were isolated (in order to exit TS 3.6.1, Containment) and subsequently repaired with Unit 2 at power.

On March 30, 2005, while addressing non-code repairs to 21, 22, and 23 CFCUs (see LER 2-05-01), NMC staff completed an evaluation that determined 24 CFCU (by itself) could perform the required safety function for Train B of containment cooling and declared Train B operable and exited LCO 3.0.3.

NRC Inspection Report 2005-003 (received by NMC on May 11, 2005) concluded that this action constituted a violation because TS Surveillance Requirements (SRs) 3.6.5.2 and 3.6.5.3 could not be met for the train with 23 CFCU isolated, thus, TS LCO 3.0.3 was improperly exited.

Subsequent to this event, NMC staff determined the repairs made to 22 and 23 CFCU were not allowed by code (see LER 2-05-01). During the May 2005 Unit 2 refueling outage, all Unit 2 fan coil faces were replaced.

EVENT ANALYSIS

The containment cooling system2 is a closed system in containment. There are two trains with two CFCUs per train. Integrity of the tubes in the CFCUs is required for containment integrity. The CFCU tubes support two safety functions: (1) circulating cooling water for containment cooling in the event of a loss of coolant accident (LOCA) or main steam line break in containment, and (2) serving as a containment boundary during the first hours of a LOCA when containment pressure will exceed the pressure of the cooling water in the CFCUs.

Since the failures to shutdown Unit 2 in accordance with TS LCO 3.0.3 resulted in a violation of Technical Specifications, it is required to be reported per 10 CFR 50.73(a)(2)(i)(B).

1 (EIIS Component Identifier: FCU) 2 (EIIS System Identifier: BK) FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6) PAGE (3) I, Prairie Island Nuclear Generating Plant Unit 2 05000306 YEAR 05 03 Impact on Safety System Functional Failure Performance Indicator The evaluation on which NMC based the restoration of Train A containment cooling to operable status determined that the safety function of containment cooling was not lost. The conclusion of this evaluation is not in question as a result of this event. Thus, this event is not reportable per 10 CFR 50.73(a)(2)(v)(C) as a Unit 2 Safety System Functional Failure (SSFF).

SAFETY SIGNIFICANCE

As noted above, NMC had reasonable assurance that the remaining CFCU in Train A of containment cooling could have performed its safety function in the event of a design basis accident. Therefore, this event did not affect the health and safety of the public.

CAUSE

This event is attributable to an NMC interpretation of TS that was subsequently determined by the NRC to not meet TS surveillance requirements.

CORRECTIVE ACTION

Immediate:

None.

Subsequent:

None required.

Planned:

1. Prairie Island Technical Specifications will be reviewed to determine if any other specifications have the same potential as TS 3.6.5 to result in the error that caused this event.

2. Prairie Island Operations and selected Management staff will be trained on this event and on the results of the review above to prevent this condition (or a similar condition) from recurring.

PREVIOUS SIMILAR EVENTS

None.