05000368/LER-2009-002
| Arkansas Nuclear One, Unit 2 | |
| Event date: | 09-07-2009 |
|---|---|
| Report date: | 11-06-2009 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3682009002R00 - NRC Website | |
10. POWER LEVEL
000
12. LICENSEE CONTACT FOR THIS LER
NAME
David B. Bice, Acting Manager, Licensing TELEPHONE NUMBER (Include Area Code) 479-858-4710
13. COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT
CAUSE SYSTEM COMPONENT MANU- FACTURER
REPORTABLE
TO EPIX CAUSE SYSTEM COMPONENT
MANU-
FACTURER
REPORTABLE
TO EPIX
14. SUPPLEMENTAL REPORT EXPECTED
- YES (If yes, complete 15. EXPECTED SUBMISSION DATE) D @ D NO
15. EXPECTED
SUBMISSION DATE
MONTH DAY YEAR
ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) (16) On September 7, 2009 at approximately 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br />, with Un't 2 in mode 6 for refueling, operators discovered that containment penetration isolation valves located on the return line of the Containment Atmosphere Monitoring System were configured such that a direct path existed between the containment atmosphere and the auxiliary building atmosphere and the resulting containment breach was not being administratively controlled as required by Unit 2 Technical Specifications. During the plant shutdown, in preparation for refueling, the system was initially placed in the correct configuration in accordance with the plant cool down procedure. However, subsequent local leak rate testing evolutions required system valve position manipulations and, following the second test affecting this system, the valve alignment was not restored to the required configuration. Core alterations commenced shortly thereafter, placing the unit in a condition prohibited by Technical Specifications. It was determined that the failure to apply proper containment closure controls was caused by inadequate procedure instructions for restoration of the affected system following local leak rate testing. Upon discovery, the system configuration was immediately re-established to comply with the Technical Specification Limiting Condition for Operation and the procedure requirements governing containment closure controls.
A. Plant Status At the time of this event, Arkansas Nuclear One, Unit 2 (ANO-2) was shutdown in Mode 6 for a refueling outage.
B. Event Description
On September 7, 2009, with the plant in Mode 6 for refueling, ANO-2 Operations personnel, while reviewing local leak rate testing results and documentation, discovered that the inside and outside containment penetration isolation valves [JM] located on the return line of the Containment Atmosphere Monitoring System [IK] were open such that a direct path existed between the containment atmosphere and the auxiliary building atmosphere. Furthermore, it was determined that these valves were not under administrative controls while core alterations were in progress as required by Technical Specification 3.9.4 and containment closure controls procedures. Upon discovery, the system configuration was immediately restored to comply with the Technical Specification Limiting Condition for Operation and the procedure requirements governing containment closure controls. The condition prohibited by the Technical Specification Limiting Condition for Operation existed from 12:50 PM CDT September 6, 2009 to 2:00 PM CDT September 7, 2009.
C. Root Cause
The Containment Atmosphere Monitoring System had previously been modified to provide the capability for alignment of the system to perform secondary functions of containment pressure and oxygen control. During normal operations, when the system is aligned to perform this function, monitored air exchange between the auxiliary building and containment is occurring.
During plant shutdown, procedures direct operators to re-align the system to terminate the air exchange between the auxiliary and containment buildings and establish a sample flow path from containment that returns to containment.
The evaluation of this event identified that following the system modification discussed above, it was not recognized that an inadequate interface existed between the local leak rate testing procedure, the normal system operating procedure and Technical Specification requirements for containment closure control. The normal system operating procedure assumed that the system would be typically aligned for oxygen and pressure control, which permits the open pathway between containment and the auxiliary building. Consequently, upon the conclusion of a local leak rate testing activity, the system was left in its normal configuration which created an open pathway from containment without the knowledge of the designated Containment Closure/Configuration Control senior operator. Subsequently, core alterations commenced without the appropriate containment closure controls that are required by Technical Specification and containment closure procedures.
D. Corrective Actions
Immediate action was taken to verify that all Containment Atmosphere Monitoring System penetration isolation valves were closed and to apply appropriate containment closure controls.
Caution cards were installed on valves used to align the system for oxygen and pressure control with instructions to verify that containment closure requirements are determined prior to opening.
To maintain continuous containment atmosphere sample flow, the penetration isolation valves for this system remain open when in their normal alignment. During plant operations in Modes 1-4, these isolation valves receive automatic closure signals from the Containment Isolation Actuation System or Safety Injection Actuation System [JE]. Procedure changes are in progress that will establish a containment to containment flow path as the normal system valve alignment, rather than the alignment for oxygen and pressure control. This change will provide an explicit system alignment to be established following testing activities that will restore containment closure for penetrations in this system.
E. Safety Significance
At the time of this event, ANO-2 was in mode 6 for refueling, and the reactor had been shutdown for greater than 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br />. There was no actual failure or degradation of equipment and no safety concern due to the small diameter of the piping involved. Additionally, normal ventilation systems were in service providing a filtered and monitored pathway for effluents from the auxiliary building atmosphere. It has been determined that there was no potential for a release resulting from a fuel handling accident that would exceed the limits of 10CFR100 at the site boundary.
F. Basis for Reportability ANO-2 Technical Specification 3.9.4 requires that, during core alterations, each penetration providing direct access from the containment atmosphere to the outside atmosphere shall be closed by a manual or automatic isolation valve, blind flange, or equivalent. This requirement is modified by a note stating that penetration flow path(s) providing direct access from the containment atmosphere to the outside atmosphere may be un-isolated under administrative controls. The aforementioned condition resulted in an open containment penetration pathway during core alterations that existed without application of the administrative controls required by the Technical Specification. Therefore, this event is reportable pursuant to 10CFR50.73(a)(2)(i)(B) as a condition prohibited by Technical Specifications.
G. Additional Information
There have been no previous similar events reported by ANO.
Energy Industry Identification System (El IS) codes are identified in the text as [XX].