ML19345G176
| ML19345G176 | |
| Person / Time | |
|---|---|
| Site: | Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png |
| Issue date: | 01/18/1974 |
| From: | Hartley F CONNECTICUT YANKEE ATOMIC POWER CO. |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| AO-74-01, AO-74-1, CYH-2569, NUDOCS 8103100200 | |
| Download: ML19345G176 (2) | |
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January 18, 1974
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Mr. James P. O'Reilly, Director 3
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Dear Mr. O'Reilly:
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As defined by Technical Specifications for Conne cut Yankee Atomic Power Station, Section 5.3, the following incident involving an unsatis-factory test of timers associated with the emergency diesel generator / core cooling systems is hereby submitted as Abnormal Occurrence 74-1.
While conducting routine surveillance tests of the core cooling equipment initiation timers, No. 3 containment recirculating fnn timer failed to actuate within the required time. The criteria for this timer is 43 5 seconds; however the timer actuated at 31.5 seconds. The timer also failed to operate properly on t o subsequent tests.
Since these, timers function to sequentially load the emergency diesel generators during a simultaneous loss of AC power and core cooling actuation, operation outside the permissible time band is considered to constitute an Abnormal Occurrence.
Redundant back up timers were satisfactorily tested to insure proper response capability and the affected timer was replaced.
However, the replacement tiner also failed to operate properly and further investigation revealed the problem to be malfunction of an SV relay located in the timer circuitry. The SV relay monitors 480V Bus 6 voltage and actuates the timer for the containment recirculating fan provided the necessary core cooling signal is present. The SV relay appeared to be sticking and would not operate consistently.
Previous diTficulty was experienced with the SV type relays in the timer circuitry during testing in October 1973 and was reported as Abnormal Cccurrence 73-9.
There are six such relays installed in this system.
The affected SV relay was replaced and successfully tested several times.
Further study is being conducted to determine if these relays have a generic problem or whether the erratic operation is related to other factors such as usage, environment, etc. Additionally, other types of relays are being studied to determine if an acceptable alternate is avail-able for this service.
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l Mr. James P. O'Reilly, Director January 18, 1974 Presently it is intended to conduct the surveillance test on a weekly With weekly basis rather than monthly to insure satisfactory operation.
tests plus redundant back-up equipment, it is felt that the system cap-ability is adequate.
Very truly yours,
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F. W. Hartley Plant Superintendent FWH/bn cc: Mr. A. Giambusso Deputy Director for Reactor Projects Directorate of Licensing U. S. Atomic Energy Commission Office of Regulation Washington, D. C. 20545 e
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r c.a January 18, 1974 CYH-2570 Mr. James P. O'Reilly, Director Region 1 Directorate of P.egulatory Operations U. 5. Atomic Encrgy Comission 631 Park Avenue King of Prus.sia, Pennsylvania 19406 Dear fir. O'Reilly.
As defined by Technical Specifications for Connecticut Yankte i
Atomic Fwer Station Section 5.3, the following information involving the malfunction of tv; nsin steam line excessive flow differential pressure transmitters is reported as Abnorral Occurrence 74-2.
At 0512 this date a data logger alam message was received indicating a main stean line high steam flos condition in the f2 steam Ifne. Two ninutes later a simliar high steam flow condition was annunciated for the f1 steam line. The coincidence of two high stezm flow signals satisfied the tripping logic and a reactor / turbine trip occurred from full pow r (s 600 MWe).
Subsequent investigation revealed frozen instrument sensing lines leading to the differential pressure tranimitters for the F1 and f2 main steam line excessive flow instrus.
The instrument sensing lines were tha ed and the instrurentation returned to norns1, The instrt[ments in question are housed in an enclosure attached to the cutside of the reactor containment.
Sub-zero temperatures and stang winds created the freezing environment. Additionally two unit heaters in the effected area were not operating.
The two unit hesters were repaired and returned to service. Other freeze protection ne3sures are currently under investigatiot Very truly yours,
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'a F. W.'H2.rtley Plant Superint ndent P.HG/bn cc:
fir. A. Giambusso Deputy Director for Reactor Projects Directorate of Licensino U. S. Atomic Energy Comission Office of Regulation
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