ML20107B679
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4 C f'l Jersey Central Powk& Light Company s[ h I
~&Y M ADISON AVENUE AT P )NCH BOWL RO AD e MORRISTOWN, ',J. 07360 e $39 6111 February 8, 1973 4
Mr. J. P. O'Reilly, Director Directorate of Regulatory. Operations, Region 1 United States Atomic Energy Commission 970 Broad Street.
Newark, New Jersey.07102 h-
Dear Mr. O'Reilly:
Subject:
Oyster Creek Station -- Docket No. 50-219 Control Rod Drive Selector Switch Failure In response to a request from Mr. F. Cantrell, we are making the following-s report as-an item of interest:
While in the process of a reactor startup, the reactor operator was unable
,to select'the next sequence rod.
It was recognized that approximately 20 control rods, which were already withdrawn, could not be moved by manual control. At this point in time, a total of 57.were withdrawn from the core. All the affected control rods could have been scrammed had it become necessary. A jumper was placed across the last switch the operator selected and all control rods were inserted in normal sequence thereby shutting the reactor down.
4 An investigation revealed that normally closed contact 1-2 of select switch 4S-14-11 had failed in the open position.
Since the circuit is arranged in a series logic configuration for all 137 rods, then all rods downstream of number 14-11 could not be selected for manual positioning. Upon replacing the selector switch (Licon switch, part number 01-365620) the circuit returned to normal.
The ability of the reactor protection system to scram all rods with a failed-select switch was never jeopardized. The subject was reviewed with the General Electric Company, who advised that DRL was aware that the rod select system was not a saf eguard system and that it was possible for these switches to f ail in this manner. A maintenance procedure has been developed to f acilitate changing the failed selector switch should this event occur while the plant is at power.
We trust you find this report fully responsive to your interest in this operating experience.
Very truly.yours, f, li Qt i Cl( g.1,
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Donald A. Ross V
Manager, Nuclear Generating Stations 2
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9604170025 960213 PDR FOIA DEKOK95-258 PDR s
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O t & Light Company
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M ADISON AVENUE AT PUNCH BOWL RO AD e MORRISTOWN. N.J. 07960 e 539 6111 February 8, 1973 qe(e$fsafe.^
Mr. F. E. Kruesi Id[
4 ge,b t Director of Regulaton Operations United States Atomic Energy Connission Washirgton, D. C. 20545
Dear Mr. Eruesi:
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Subject:
Oyster Creek Station Docket No. 50-219 Personnel Radiation Overexposure l
'Ihe attached report ' details the information surrounding the
. overexposure of three of our personnal at the Oyster Creek Nuclear Generating Station on January 1,1973 and is being submitted in accord-ance with the requirements of 10CFR20, paragraph 20.405(a)(1). According to tha raquirancras in patwgropii 20.403(c), each of the -3ndividuels notec in Enclosure 1 will be notified regarding the nature and extent of overexposure.
Upon discovery of the condition, gmater controls were inmediately instituted to prevent a recurrence of the situation and more stringent requirements will be instituted with regard to sampling frequency and access control for future maintenance activities.
Very truly yours, L > Cct-d ec-d I
Donald A. Ross Manager, Naclear Generating Stations pk Attachments 4
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J. P. O'Reilly, Director Directorate of Regulatory Operations, Region 1 9
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a TEPORT OF GTHEXPOSURES As a result of the reactor scra1 on December 29, 1972 and the attendant problems which were experienced, all five relief valves wem being removed from the main steam lines for inspcc: ion and ultimate modifi-cation. Du"ing the initial stage of this maintenance period, three indi-viduals were expesed to concentraticns of radioactive material in excess of the amounts c;ccified in Appendix B, Table 1, Colu n 1 of 100FR20. A description of the incident follows:
On December 31, 1972, sa :ples taken of containment airborne concentrations were such that access to the containment was unlimited (168 hours0.00194 days <br />0.0467 hours <br />2.777778e-4 weeks <br />6.3924e-5 months <br />) for the maintenance activities involved. A routine contairnent air sa@ le taken at 8: 15 a.m., January 1,1973, indicated an increased airborne concentration over the prev $ous day with the maior contributor, and in fact the only contributor of significance, being XelD3 Access was pemitted to the cont:1rraent but with a reduced stt.y tlats of 15.7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />. Based upon this fact, an increased sampling frequency was initiated and an investigation ccamenced in an effort to detemine the source of this activity. A second samgle,takennea"lyanhourlaterat9:10 a.m., indicated the levels of Xel 3 had measurably increased, reducing the stay tim to 12 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />. It was decided at that tire to count still a third sample after being in service for a shorter tim interval. Tentative plans were made to stop all work in the contairmnt if the sample showed an increasing airborne level which noula limit access to five hours or less. Forty minutes later, at 9:50 a.m.
the sam le was counted and it was discovered that the levcla cf Xe' %,had again acie than dadaleQ ho ever, the suissequeul, access time was reduced to only 6.1 hours1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and maintenance activities were pennitted to ' continue particularly in light of the fact that a work break was less than two h u away.
By this time, the source of activity had been detennined to be originating from the open relief valve flanges which were being cleaned up by several mechtnics. Preparations were made to start the cordenser mechanical vacuum pump and to perform the valving required in the main steam system so that the gasses ccming out of the reactor coolant could be eva'cuated to the condenser instead of diffusing into the primary contair;aent atmosphem. Directions were given to tightly cover any of j
the re reinirG cp;n relief valve flanges and to insure that prior to j
pmceeding to work on rny mne f3an;es airflow would be checked to be in the inward airection.
In additicn, the contairmnt airlock interlock j
nechanism ' as mah up requiring that at least one of the two airlock doors be closed at all times and there'ay insuring that the contairmnt atmosphere was being evacuated via its nonnal path. However, the fourth l33 concentration of 4.76 x 10" i
sample taken at 11:25 a.m. indicated a Xe pc/ml which limited the allowable stay time to just less than on2 hour.
By the tire the sa ple had been analyzed and calculated, all persorml in the contairmant had stopped work for their normal break.
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2 At that time, access to the contairment was restricted until further canples could be taken and the airborne activity ft und to have decreased to more acceptable levels.
Preliminary calculations were made which indicated that three personnel were in the containment durirs the period of time involved so that the requirements of 10CFR20, paragraph 20.103(b) were not met. 'Ibe extent of the occupancy tina ranged frcc 37% to 51% above the j
allowable tine lLmits. Instructions were given to prevent these affected personnel fren gaining access to any area of the plant where airborne activity conceritrations were of such a nature that access would not be unlimited. In addition, the increased contairment air samplirq frequency was raintained and a more strict criteria fer access was instituted to insure that no additional personnel overexposures occurred as a result of abnorral concentrations of airborne activity. This, coupled with the operation of the mchanical vacur nu,, the coverir6 cf the relief valve flange openings, and the :raintenance 6f the contairment airlock interlock, prevented any further exposure problems durir6 the progress of maintenance work in the contairment.
. lists the personnel involved, the average concentrations of Xel33 and Xe135 to which they were exposed, the permissible stay tires based upon the average concentrations, the period of time actually within the containment, and the estimated extent of excessive exposure during this period.
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Measures will be taken during future maintenance activities to sanple airborne concentrations at a greater frequency when open flanges to the reactor coolant system exist and to make provisions, if possible, to insure that activity cannot diffuse into the surrounding atmosphere.
Additionally, more stringent limits vill be inposed on access criteria to areas of airborne radioactivity concentrations and plottirc of any unanticipated charges in concentration will tc initiated to permit basing access decisions on the anticipated future trerd.
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