05000313/LER-2005-001
| Arkansas Nuclear One - Unit 1 | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3132005001R00 - NRC Website | |
A. Plant Status At the time this condition was discovered, Arkansas Nuclear One, Unit 1 (ANO-1) was in a scheduled refueling outage with fuel handling activities in progress in the reactor building [NH].
B. Event Description
ANO-1 Technical Specifications (TS) requires super particulate iodine noble gas (SPING) effluent monitor, SPING-1 [IL], to be operable when the reactor building purge isolation valves are open and fuel movement is in progress in the reactor building. If the SPING becomes inoperable, TS requires the movement of irradiated fuel to be suspended immediately. On October 13, 2005, SPING-1 was removed from service for 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and 43 minutes, with fuel movement in progress in the reactor building. Fuel movement was not suspended as required.
SPING-1 is a self-contained microprocessor-based radiation detection system for monitoring particulate, iodine and noble gases in the reactor building ventilation system [VA]. On October 13, 2005, chemistry personnel requested permission from the control room to remove SPING-1 from service to perform surveillance testing in accordance with Off Site Dose Calculation Manual (ODCM) requirements. The ODCM requires weekly sampling of active effluent pathways. Although fuel offload was in progress at the time, operations personnel did not recognize that the removal of SPING-1 from service was prohibited by TS and granted chemistry personnel permission to remove SPING-1 from service for sampling. Sampling was performed and SPING-1 was returned to service.
On October 14, 2005, chemistry personnel again requested permission to remove SPING-1 from service for sampling. At this time, operations personnel in the control room recognized that this configuration was not allowed with fuel movement in progress in the reactor building.
Operations personnel further realized that the removal of SPING-1 from service the previous day was performed during fuel movement, thus resulting in operation prohibited by TS.
C. Root Cause
This event can be attributed to inadequate guidance regarding the TS requirement to maintain SPING-1 operability during fuel movement in the reactor building.
The chemistry procedure used to perform sampling of Unit 1 vents did not require verification that fuel movement was not in progress in the reactor building prior to the removal of SPING-1 from service.
The TS requirement for SPING-1 to be operable to maintain the reactor building purge isolation valves operable during fuel movement was not common knowledge among the operations staff.
D. Corrective Actions
Chemistry procedures will be revised to ensure SPING-1 is not removed from service during fuel handling operations in the reactor building unless TS requirements are satisfied.
The requirement to verify SPING-1 operability was clarified in operations procedure 1502.004, "Control of Unit 1 Refueling," Attachment B, to ensure the TS requirement for maintaining the SPING operable during refueling operations is met.
This event was incorporated into the operations continuing training program to increase operator cognizance of the requirement to maintain SPING-1 operable during fuel handling in the reactor building when the reactor building purge valves are required to be operable.
E. Safety Significance
Spent fuel assemblies are handled entirely under water. Before refueling, the boron concentrations of the reactor coolant and the fuel transfer canal water above the reactor are increased so that, with all control rods removed, the core will not become critical. Although mechanical damage to the fuel assemblies during transfer activities is improbable, a mechanical damage type of accident is considered the maximum potential source of activity release during refueling operations. The offsite dose consequences from gases released during a fuel handling accident directly to the atmosphere with no filtration, assuming the reactor has been shut down for 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> (TS prohibits fuel handling operations prior to this time), will not exceed 25 percent of 10CFR100 limits. Therefore, this condition had minimal safety significance.
F. Basis for Reportability Technical Specification 3.9.3 requires each penetration providing direct access from the reactor building atmosphere to the outside atmosphere to be capable of being closed by an operable reactor building purge isolation valve with the purge exhaust radiation monitoring channel operable. With a reactor building penetration not in the required status, movement of irradiated fuel assemblies within the reactor building is to be suspended immediately.
Movement of irradiated fuel assemblies on October 13, 2005, with SPING-1 inoperable resulted in operation prohibited by TS. This report is submitted in accordance with 10CFR50.73(a)(2)(i)(B).
G. Additional Information
There have been no previous similar Licensee Event Reports submitted by ANO.
Energy Industry Identification System (ENS) codes are identified in the text as [XX].