ENS 46283
ENS Event | |
|---|---|
12:40 Sep 22, 2010 | |
| Title | Unexpected Changes in Restricted Area Dose Rates |
| Event Description | On Wednesday morning, September 22, 2010, the Senior Reactor Operator (SRO) pulled some oil samples, housed in aluminum racks, out of the well groove around the reflector near the top of the reactor where the samples had been exposed to radiation for 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> and then allowed to decay for 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. When the samples and sample holder were removed from the pool, three detectors alarmed: two were expected to alarm, and a third, the Control Room Evacuation Alarm, was not expected to alarm. The Control Room Evacuation Alarm has a conservative, audible, alarm set point of 2.5 mR/h which is well below the actual evacuation threshold of 100 mR/h. The Control Room Evacuation Alarm alerted the SRO that conditions were not normal. Within 30 seconds, the SRO placed the aluminum sample holder behind a lead shield and the oil samples behind a beta shield. According to facility procedures, the facility did not need to be evacuated because the easily visible Control Room Evacuation Alarm meter had not exceeded the evacuation threshold of 100 mR/h.
The SRO estimated his dose as being approximately 1 Rem Total Effective Dose Equivalent (TEDE) which is less than the 5 Rem/yr, Part 20 limit; and approximately 15 Rem extremity dose which is less than 50 Rem/yr Part 20 limit. Follow-up dosimetry reports indicated that the SRO only received 147 mRem deep dose and 148 mRem shallow dose. No members of the public were in the vicinity at the time of the event. The facility believes that the cause of the high radiation field was possibly due to a high level of impurities in the aluminum sample holder and not from the oil samples. However, the oil samples received greater than normal neutron exposure and shorter than normal decay before removal from the reactor pool. This particular experiment required that these samples decay for only 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, whereas normally, a decay time of 2 to 5 days is required before the samples are removed from the pool. The Reactor Safeguards Committee has recommended that the facility perform irradiation tests on each of its sample holders to prevent unexpectedly high radioactivity from unknown impurities. Kansas State University is making this report per their license requirements and Technical Specification 6.9.a.6, an observed inadequacy in the implementation of either administrative or procedural controls, such that the inadequacy has caused the existence or development of an unsafe condition in connection with the operations of the reactor. The State of Kansas has been notified of this event. |
| Where | |
|---|---|
| Kansas State University Manhattan, Kansas (NRC Region 4) | |
| License number: | R-88 |
| Reporting | |
| Non | |
| Time - Person (Reporting Time:+121.12 h5.047 days <br />0.721 weeks <br />0.166 months <br />) | |
| Opened: | Jeffrey Geuther 13:47 Sep 27, 2010 |
| NRC Officer: | Eric Simpson |
| Last Updated: | Sep 27, 2010 |
| 46283 - NRC Website | |
Kansas State University with Non | |
WEEKMONTHYEARENS 544212019-12-05T00:00:0005 December 2019 00:00:00
[Table view]Non Annual Surveillance Not Completed ENS 538052018-12-22T06:00:00022 December 2018 06:00:00 Non Surveillance Not Done Due to Inadequate Procedure ENS 529802017-09-19T19:49:00019 September 2017 19:49:00 Non Reactor Bay Ventilation Inoperable ENS 491172013-06-13T20:39:00013 June 2013 20:39:00 Non Failure of In-Core Thermocouple ENS 462832010-09-22T12:40:00022 September 2010 12:40:00 Non Unexpected Changes in Restricted Area Dose Rates 2019-12-05T00:00:00 | |