05000338/LER-2002-001
| Document Numbersequential Revisionmonth Day Year Year Month Day Year North Anna Power Station, Unit 2 05000-339Number Number | |
| Event date: | 06-25-2002 |
|---|---|
| Report date: | 08-06-2002 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3382002001R00 - NRC Website | |
LER NUMBER (6) PAGE (3)
NORTH ANNA POWER STATION
1.0 DESCRIPTION OF THE EVENT On June 25, 2002, at 1330 hours0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.06065e-4 months <br />, with Units 1 and 2 in Mode 1 operating at 100% power, it was discovered, during the review of Technical Requirement Manual changes that were being performed to support the conversion to the Improved Technical Specifications, that the alarm setpoint for the Waste Gas Decay Tank (WGDT) Oxygen Analyzer (EIIS System WE, Component AA) may allow the tank oxygen to exceed the limit of Technical Specification (TS) 3.11.2.5. TS 3.3.3.11 requires the oxygen monitor to be operable with the alarm setpoint maintained to ensure the limits of TS 3.11.2.5 are not exceeded. TS 3.11.2.5 requires that the concentration of oxygen in the WGDTs be limited to less than or equal to 2% by volume whenever the hydrogen concentration could exceed 4% by volume.
Procedures ICP-GW-1-02-102, Waste Gas Decay Tank Outlet Oxygen and 1-PT-45.9.3, Waste Gas Decay Tank Outlet Oxygen Functional (ITS Operational) Test (02-GW-102), use an alarm setpoint of 2% (1.800 VDC on a 1 - 5 VDC scale, analogous to 0 — 10% oxygen). An acceptable range of plus or minus 0.5% was applied to this setting, giving an upper end value of 1.820 VDC. This upper end value translates to 2.05% oxygen, which is in excess of the TS limit of less than or equal to 2% oxygen by volume.
A review of completed performances of ICP-GW-1-02-102 and 1-PT-45.9.3 was performed for the period of January 2001 through June 2002 in an effort to determine if there were other instances where the WGDT oxygen analyzer setpoint was set incorrectly. This review identified several instances where the WGDT oxygen analyzer alarm setpoint was set above the 2% oxygen limit specified by TS 3.11.2.5. However, it was also verified that the indicated oxygen level in the WGDTs was less than or equal to 2% during this timeframe. Therefore, this event is being reported as a condition prohibited by TS in accordance with 10CFR50.73(a)(2)(i)(B).
2.0 SIGNIFICANT SAFETY CONSEQUENCES AND IMPLICATIONS The gaseous waste disposal system is designed to provide adequate storage for radioactive decay time of waste gases. The system contains two WGDTs that are provided with overpressure relief protection to preclude leakage of waste gas to the environment during normal operation. The hydrogen and oxygen concentrations in the WGDTs are monitored to prevent an explosive gas mixture. The monitoring of the WGDT oxygen concentration is performed by Operations every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> to verify the WGDT oxygen levels are maintained less than or equal to 2% by volume with the hydrogen concentration typically maintained greater than 4% by volume. After sufficient decay time, the gases in the WGDTs are released through the process vent system to the atmosphere.
FACILITY NAME (1) DOCKET PAGE (3) LER NUMBER (6) The WGDT rupture is an analyzed event. Although no specific cause for a rupture has been defined, the analysis assumes that a WGDT rupture takes place when the tank has the greatest inventory of waste gases at the maximum expected activity. The entire gaseous content of the WGDT is assumed to be releases in a ground-level release. The dose consequence from a rupture of a WGDT is well below the guidelines of 10CFR100.
Based on the design of the gaseous waste disposal system, the monitoring and verification that WGDT oxygen levels are maintained less than or equal to 2% by volume, and the consequences from a postulated WGDT rupture being well below 10CFR100 guidelines, this event posed no significant safety implications. Therefore, the health and safety of the public were not affected by this event.
3.0 CAUSE The cause of the event is attributed to personnel error that resulted in the establishment of inadequate calibration and functional test procedures that did not satisfy TS requirements.
An incorrect acceptable range with an upper end value that exceeded TS limits had been inadvertently incorporated into the calibration and functional test procedures.
4.0 IMMEDIATE CORRECTIVE ACTION(S) The action statement requirement of TS 3.3.3.11 was entered, at 1330 hours0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.06065e-4 months <br /> on June 25, 2002, upon discovery of the discrepancy.
The oxygen analyzer alarm setpoint was adjusted from 1.808 VDC to 1.786 VDC to be within the TS limit. The action statement requirement of TS 3.3.3.11 was cleared at 0408 hours0.00472 days <br />0.113 hours <br />6.746032e-4 weeks <br />1.55244e-4 months <br /> on June 26, 2002.
5.0 ADDITIONAL CORRECTIVE ACTIONS Procedures ICP-GW-1-02-102, Waste Gas Decay Tank Outlet Oxygen and 1-PT-45.9.3, Waste Gas Decay Tank Outlet Oxygen Functional (ITS Operational) Test (02-GW-102), were revised to correct the upper end of the acceptable range value to ensure TS requirements are met.
6.0 ACTIONS TO PREVENT RECURRENCE No further actions are required.
FACILITY NAME (1) DOCKET LER NUMBER (6) 7.0 SIMILAR EVENTS failed to include a functional test of the high oxygen alarm associated with the WGDT hydrogen/oxygen analyzer. The cause of the event was attributed to personnel error due to a failure to develop adequate procedures to cover TS requirements.
8.0 MANUFACTURER/MODEL NUMBER Not Applicable 9.0 ADDITIONAL INFORMATION None