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Information Notice No. 83-75: Improper Control Rod Manipulation
SSINS No.: 6835 IN 83-75 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C., 20555 November 3, 1983 Information Notice No. 83-75: IMPROPER CONTROL ROD MANIPULATION Addressees: All nuclear power reactors holding an operating license (OL) or construction permit (CP). Purpose: This information notice is provided as a notification to licensees of improper control rod manipulations. The improper manipulations were used because of inadequate communications from and controls by plant management. It is expected that recipients will review the information for applicability to their facilities. Description of Circumstances: On March 10, 1983, Unit One at Quad Cities Station was being shut down in preparation for a weekend maintenance outage. The operators were inserting rods using what they thought was an approved "fast shutdown sequence" provided by the station nuclear engineers. They were actually using a rod worth minimizer (RWM) computer printout that had been attached to the approved sequence. The RWM computer printout listed the rod groups to be inserted in reverse order of the actual sequence required. As the shutdown continued the operators attempted to activate the RWM according to the normal unit shutdown procedure. The RWM immediately produced a rod block and indicated that rod insertion errors had occurred. After discussing the situation with the shift supervisor, it was decided that the RWM should be declared inoperable and bypassed. The shutdown continued with the shift supervisor acting as the independent rod verifier using the RWM computer printout as the assumed correct sequence. At approximately 10% power, the turbine generator was tripped and the reactor was manually scrammed as part of the normal shutdown. On the following morning, March 11, 1983, plant management discovered that the control rods had been inserted in reverse order using the RWM computer printout. On July 14, 1983, Hatch Unit 2 was operating at about 25% power, following a startup after a refueling outage, when condenser vacuum began to decrease. It was apparent to the plant operators that there was a problem with the steam jet air ejector and reactor power would have to be decreased to start a mechanical vacuum pump to prevent the loss of a reactor feed pump and a reactor 8308310075 . IN 83-75 November 3, 1983 Page 2 of 2 scram. The operators began to insert rods using the approved rod sequence, but because of the low worth of the control rods in this portion of the sequence, the power was not being decreased at the desired rate. At this time a decision was made by licensed operators and the shift technical advisor to insert rods using the Rod Out Notch Override Switch in the emergency in position and by individually scramming rods from the scram test panel. The operators did not have any approved procedure for this type of shutdown and defeated the rod sequence control system (RSCS) and the RWM. When the mechanical vacuum pump was put into service at a reduced power level and the vacuum had stabilized, an operator found a control rod in an out-of-sequence position, The operator then manually scrammed the unit following a plant procedure concerning out-of-sequence control rods. Discussion: The events, described above did not result in fuel damage, but affected the plants' ability in a rod drop accident. The control rod sequence, the RWM, and the RSCS are all used to mitigate the consequences of a control rod drop accident. The misuse of these protective features could result in fuel damage. Plant managers should train and properly communicate to their operators the importance of these protective features and the adherence to approved rod sequence procedures. No written response to this notice is required. If you have any questions regarding this matter, please contact the Regional Administrator of the appropriate NRC Regional Office, or this office. Edward L. Jordan Director Division of Emergency Preparedness and Engineering Response, IE Technical Contact: Paul R. Farron, IE (301) 492-4766 Attachment: List of Recently Issued IE Information Notices .
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