ML052230398
| ML052230398 | |
| Person / Time | |
|---|---|
| Site: | National Bureau of Standards Reactor |
| Issue date: | 08/10/2005 |
| From: | Myers T US Dept of Commerce, National Institute of Standards & Technology (NIST) |
| To: | Mendonca M Office of Nuclear Reactor Regulation |
| References | |
| Download: ML052230398 (3) | |
Text
Marvin Mendonca - Docket Number 50-184 Page From: "Tom Myers" <tjmyerstnist.gov>
To: "'Marvin Mendonca'" <MMM~nrc.gov>
Date: 8/10/05 1:51 PM
Subject:
Docket Number 50-184 We wish to provide a more detailed description of an occurrence from July 27, 2005. While the occurrence is not reportable, we are providing these details for your information only.
A shutdown of the reactor was made on July 24, following a normal operating cycle. An extended maintenance period began on July 25. On July 27, the control room reactor operator used a key switch to administratively turn on the reactor to allow technicians to complete a shutdown scram response test for a flow instrument. Following the ten minute test and immediately after returning the key switch to OFF, the operator realized that the key switch position should not have been changed for the test and notified the Deputy Chief Nuclear Engineer. As a prompt remedial action, red danger tags were issued immediately for the control power and rod drive power key switches, preventing further operation of the switches. Other actions were taken that day and will continue as appropriate to each member of the Reactor Operations group.
One of our technical specifications define the reactor to be shutdown when the control power key and the rod drive power key switches are locked in the OFF position. This reactor cannot go critical from a shutdown condition with the control power key switch in OFF, the rod drive power key switch in OFF, a scram condition present, a rundown signal present, or a withdraw prohibit signal present. A rundown signal causes the control rods to move in at a normal speed and a withdraw prohibit signal prevents the rods from moving out (up) from an existing position. Once the reactor operator turned the control power switch to the ON position, he administratively turned the reactor on, which was not compatible with the facility configured for maintenance; that is, two Limiting Conditions for Operation (LCO) were not satisfied with the key switch ON. However, it was not possible to move any rod from its bottom position, let alone go critical, as the power for the rod motors was never turned on, multiple rundown signals were present, multiple withdraw prohibit signals were present, and multiple and intermittent scram signals were present. With only the control power key switch in the ON position, neither LCO is relevant to the safe operation of the facility. Thus, placing red danger tags to prevent movement of either key switch again was the correct prompt remedial action.
Actions taken to date include:
- Danger tags issued
- Immediate briefing of all operators, as each becomes available Plan refresher training in the near future on the key switch circuits
Marvin Menidonca - Docket Number 50-184 Marvin Mendona .- D et .. mber 50;-1 84.= Page 211
- Prepare a revision of the applicable technical specification which would more accurately state the desired requirement.
Sincerely, Thomas Myers Deputy Chief Nuclear Engineer NIST Center for Neutron Research CC: "'Craig Bassett'" <CHB1 @nrc.gov>
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Subject:
Docket Number 50-184 Creation Date: 8/10/05 1:48PM From: "Tom Myers" <tjmyers@nist.gov>
Created By: tjmyers @nist.gov Recipients nrc.gov owf4.po.OWFN_DO MMM (Marvin Mendonca) nrc.gov AThPO.ATLDO CHB 1 CC (Craig Bassett)
Post Office Route owf4_po.OWFN_DO nrc.gov ATLPO.ATLDO nrc.gov Files Size Date & Time MESSAGE 2888 08/10/05 01:48PM TEXT.htm 6124 Mime.822 10972 Options Expiration Date: None Priority: Standard Reply Requested: No Return Notification: None Concealed
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