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Information Notice No. 92-73: Removal of a Fuel Element from a Research Reactor Core While Critical
UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR REACTOR REGULATION WASHINGTON, D.C. 20555 November 4, 1992 NRC INFORMATION NOTICE 92-73: REMOVAL OF A FUEL ELEMENT FROM A RESEARCH REACTOR CORE WHILE CRITICAL Addressees All holders of operating licenses or construction permits for nuclear power reactors. Purpose The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alert licensees to a recent event in which licensed operators at a research reactor inadvertently removed a fuel element from a reactor core that was critical. It is expected that recipients will review the information for applicability to their facilities and consider actions, as appropriate, to avoid similar problems. However, suggestions contained in this information notice are not NRC requirements; therefore, no specific action or written response is required. Description of Circumstances On June 8, 1992, at the University of Michigan's (the licensee's) Ford research nuclear reactor facility the Assistant Reactor Manager for Operations (ARM) and two other senior reactor operators (SROs) were conducting tests to measure changes in core reactivity. In each test, the operators would perform the following: move the fuel, bring the reactor to low power, collect data, and shut down the reactor. After collecting data following the third fuel movement, and with the reactor still critical at low power (8 kW), the ARM directed the two SROs to move the fuel a fourth time. The SRO acting as the control room operator then informed the ARM that the 2-hour control room log readings were due. The ARM then gave the SROs instructions on what to do while he obtained the log readings. The ARM subsequently told the NRC that he instructed the SROs to prepare for the fourth move; however, the SROs believed that they had clear direction to move fuel. The SROs then began moving the fuel. While one SRO monitored the test, the other latched a fuel element with the fuel handling tool, and then removed the fuel element. The research reactor immediately went subcritical and the control rod's servo-mechanism switched out of automatic control. At that time, another SRO not directly involved in the fuel movement, but recognizing what had happened, entered the control room and manually inserted the shim rods and control rod. The equipment performed as designed and the reactor remained in a safe condition. 9210290204. IN 92-73 November 4, 1992 Page 2 of 3 Discussion As discussed in NRC's Augmented Inspection Team (AIT) Report No. 50-002/92001, dated July 9, 1992, and associated correspondence, several factors led to this event. 1. There was frequent informal turnover of control room responsibilities between the ARM and the control room operator during the fuel movements. Who was to have overall control of the reactor between the third and fourth fuel movements was not clearly established. 2. The ARM and the other two SROs moving the fuel did not communicate well. For example, both SROs believed that they had clear instructions to move the fuel, while the ARM believed that he only instructed them to prepare to move fuel. An intercom system between the control room and the fuel handling bridge was not used until the fuel element was being moved. 3. Relying on their experience and the routine nature of the fuel moves, the SROs did not use or review the procedures that applied to moving fuel either before or during the actions to move the fuel. 4. An excessive work load may have contributed to the event. For example, the NRC inspectors found that, after correcting a previous problem with the control and shim rod magnets, the SRO's had only four hours during their normal shift schedule to complete the planned fuel moves. This was said to create a rushed atmosphere for the test activities. In moving the fuel element while the reactor was critical, the two SROs handling the fuel indicated that they did not clearly know the condition of the reactor when they removed the fuel element. The ARM did not maintain adequate control over the entire test activity. The distraction of completing the control room log contributed to poor communications with the other SROs. The licensee has modified its procedures and will install illuminated indicators on the rod drive housing located on the bridge. The indicators will be illuminated only when the rods are fully inserted. These changes to the procedures and equipment will give more positive communication, enable operators to better control fuel changes, and visually indicate the status of the control rods. This event is an example where licensed operators at a research reactor became so involved in tasks that they failed to maintain adequate control of the reactor. The operators did not maintain current knowledge of the condition of the reactor and therefore were not cognizant of the effect that their actions would have on that condition. . IN 92-73 November 4, 1992 Page 3 of 3 This information notice requires no specific action or written response. If you have any questions about this matter, please contact the technical contact listed below or the appropriate Nuclear Reactor Regulation (NRR) project manager. ORIGINAL SIGNED BY Brian K. Grimes, Director Division of Operating Reactor Support Office of Nuclear Reactor Regulation Technical contact: Charles Cox, RIII (708) 790-5298 Project Manager: Theodore S. Michaels, NRR (301) 504-1102 Attachment: List of Recently Issued NRC Information Notices .
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