This letter details an incident reported to Mr. D. Hunnicutt by telephone on June 13, 1973. At 1737 on June 13, 1973, with the Zion Unit 1 reactor in a cold shutdown condition, the reactor coolant system was pressurized to 1290 psig. Tech Spec Liniting Condition of Operation for system integrity, paragraph 3.3.2.A limits system pressure for the existing temperature of 105°F to 530 psig reference Figure 3.3.2-2 Reactor Coolant System Cooldown Limitations at a cooldown rate of 0°F/hr. Safety Implications: System integrity has not been jeopardized by the overpressurization šince the reactor vessel temperatures were above the NDT temperatures as listed in Tech Spec Table 3.3:2-1 and the vessel has received no neutron exposure upon which Figure 3.3.2-2 is based. Investication and Evaluation: At the time of the incident the reactor coolant system was solid and being maintained at pressures up to 400 psig by intermittant running of a charging pump. The normal pressure control method of continuous charging and letdown was not being used since the volume control tank was unavailable due to repair of the discharge relief valve line on 1C Charging Pump. At 1730 the 1A Charging Pump, with suction from the refueling water storage tank and discharge aligned to the charging heador, was started to increase system pressure which had reduced to 110 psig. System pressure increased gradually. During the maneuver, the Unit 1 nuclear station operator was distracted by a telephone call end leży the area of the pump control switch. Fressure increased to 1290 psig before the XIV-26 was returned to normal after the pressurizer power relief valve was manually opened. An attempt to reduce pressure using the excess letdown path was unsuccessful. Subsequent Investigation: The investigating committee interviewed Lee cups, sulit Engineer and Wally Sopata, NSO on Unit 1, concerning the incident. Results of the discussions indicate that: 1. 2. 3. 4. The procedure of pressurizing the system in the described manner had been going on for several days. Both Sues.. and Sopata were familiar with the method and had accomplished proper pressurization a number of times. The residual heat removal system suction relief valve The RHR system isolated at 600 psig, preventing over- Pressure could not be reduced using the excess letdown Mechanical and Structural Engineering department, at the request of J. S. Bitel, evaluated the incident to determine if structural damage could have occurred. Conclusions and Corrective Action: The station committee, after review of N 4 3 2ngineerings report and their own · investigation, concluded that no structural damage resulted. The procedure for pressurization was changed to require the operator to maintain contact with the pump control switch during the pump run. All operators and supervisors were so instructed. Excess letdown flow was tried after the volume control tank was available and flow and pressure indication were normal. The RHR system suction relief valve will be removed and tested at the earliest opportunity. This requires isolating both RHR trains with the system in cold shutdown. The discharge relief valves were visually inspected and will prevent RHR overpressure during cooldown. Very truly yours, J. 8. Butel J. S. Bitel Station Superintendent Shiloh Diva & Lake Michigan Te:ephone 312/746-2C34 713 1715 This letter is in response to your letter of June 25, 1975 requesting additional information in regard to Abnormal Occurrence Report No. 50-295/75-12. In response to question 1) of that letter, the following items should be noted: 1. 2. 3. The operator failed to stop the centrifugal charging The shift supervisor had reviewed the requirement to stop The RFR system procedures did not include a section on In response to question 2) of the letter regarding corrective action to prevent reoccurrence, a procedure has been written for replacing the AHR suction relief valve while in the cold shutdown condition. For a long term solution, the station is investigating the possibility of installing a relief valve to protect the RCS from overpressurization while the unit is in the cold shutdown condition. A written copy of the overpressurization occurrence and its potential consequences has been distributed to affected operating personnel to stress the importance of preventing an overpressurization of the RC3. J.r. titl J. S. Bitel Station Superintendent Zion Greatesttun Telephone 312/740-2034 June 13, 1975 ~6/24/15 Enclosed please find Abnormal Cccurrence Report No. 50-295/75-12 for Zion Generating Eterion. is abnormal occurrence vas reported to Region III, Directorate of Regulatory Operations by telephone on June 4, 1975 and by telegram on June 4, 1975. This report is submitted to you in accordance with the requirements of the Technical Specifications, Section 5.5.3.1 Very truly yours, you is faced Jack S. Sitel JS5/bjh Enclosure: Abternal Cccurrence Report No. 50-295/75-12 9 S 61 25 DOCKET NUMILA EVENT DATE 69 75 musten to replace. suction relief valve, the 18 cannoÖral connain, རན་...་ and not immediately shut off, causing the ROS pressure to increrse from 100 to 1100 psix within ten minutes. The changing rumo vas shut 5 off and system pressure was reduced to 150 psig within inutes Operator error was the cause of the RCS pressure transient. Che importance of following overating procedures was stressed to the FACT,ITY 89 TYPE 89 L 09 633 ACTIVITY 121 PERSONNEL EXPOSURES 1010 101 89 AMOUNT OF ACTIVITY 10 11 TYP & DESCRIPT C N.A. 12 13 CISCRIPTION 11 12 PERSONNEL INJURES 09 1010 101 09 UFFSITE CONSEQUENCES LOSS OR DAMAGE TO FACILITY 10 DESCRIPTION PUBLICITY 69 ADDITIONAL FACTORS N.A. N.A. N.A. N.A. |