05000285/LER-2009-001
| Telephone Number (Include Area Code) | |
| Event date: | 01-12-2009 |
|---|---|
| Report date: | 03-13-2009 |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 2852009001R00 - NRC Website | |
BACKGROUND
The radioactive waste gas system provides a means to collect, store, process, analyze, monitor, and dispose of radioactive waste gas to protect plant personnel and the public from exposure to radiation. The system collects radioactive gasses from the plant, then processes and stores the gas for release. The system consists of two Waste Gas Compressors (WD-28A/B), four Waste Gas Decay Tanks (WD-29A/B/C/D), a gas analyzer (to ensure an explosive mixture is not formed in the Waste Gas System) and associated piping.
Technical Specification (TS) 2.9 states:
(1) The concentration of hydrogen and oxygen in the waste gas decay tanks shall be limited to below flammability concentrations. With hydrogen and oxygen concentrations above flammability concentrations, restore the concentrations to below flammability limits within 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />.
(2) The hydrogen and oxygen monitors shall be monitoring the inservice gas decay tank during the transfer of waste gases to the waste gas decay tank. Whenever the monitors are inoperable, transfer of waste gases to a gas decay tank may continue provided grab samples are taken from the gas decay tank and analyzed:
a. Every eight hours during degassing operations, and b. Daily during other operations.
The Updated Safety Analysis Report (USAR) states that the waste gas constituents are, in part:
- Hydrogen, percent Trace to 3 max � *Oxygen, percent Trace to 3 max * Hydrogen, depending on the amount of reactor coolant leakage or plant evolutions in progress such as degassing, can exceed 3 percent concentration in the waste gas. However, hydrogen and oxygen gas concentrations will not exceed 3 percent at the same time.
EVENT DESCRIPTION
On January 12, 2009, at 1513 Central Standard Time, Waste Gas was pumped from the Vent Header to Waste Gas Decay Tank WD-29B. The Waste Gas Analyzer was aligned to sample Waste Gas Decay Tank WD-29D. The Waste Gas was not transferred to the tank that was being sampled. This is a violation of TS 2.9(2).
After the operator had completed the Waste Gas Transfer he realized that he had pumped to the wrong tank. The Control Room was immediately notified and the Waste Gas Analyzer was aligned to sample Waste Gas Decay Tank WD-29B. The sample confirmed that the concentrations of hydrogen and oxygen were below the flammability limits.
Actual concentrations were 0.46 percent hydrogen and 0.61 percent oxygen. This event is being reported pursuant to 10CFR50.73(a)(2)(i)(B).
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CONCLUSION
A root cause analysis determined that the reason for not complying with the TS was the inappropriate use of turnover logs as the sole method to track long term off-normal plant status information. This resulted in insufficient system status information barriers (labels, tags, etc.) being present to remind operators of the off-normal alignment of the Waste Gas System.
CORRECTIVE ACTIONS
A sample was obtained and it verified that the gas in the tank did comply with TS 2.9(1) as required.
Criteria have been developed for weekly review of turnover sheets to ensure sufficient status control barriers for components (labels, tags, etc.) are in place. A weekly preventive maintenance task has been created for the Shift Manager to review turnover logs and ensure status control barriers (labels, tags, etc.) are in place using the developed criteria.
SAFETY SIGNIFICANCE
The gas monitor provides an early warning to the operators if a flammable mixture of gas is being transferred to the waste gas tank. While it is possible for the gas mixture in the vent header to contain a flammable mixture, in this instance, the gas mixture in WD-29B was well within the flammable limits for the gasses. A flammable mixture did not exist, therefore there was no impact to the health and safety of the public due to this incident.
SAFETY SYSTEM FUNCTIONAL FAILURE
This event does not result in a safety system functional failure in accordance with NEI-99-02.
PREVIOUS SIMILAR EVENTS
FCS has not had any previous similar events with the waste gas disposal system.
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