ML20029A746
| ML20029A746 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 02/28/1991 |
| From: | Denton R BALTIMORE GAS & ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9103040200 | |
| Download: ML20029A746 (2) | |
Text
..
s t3 A L, r t M CRC OAS AND ELECTRIC CHARLES CENTER e P.O. DOX 1476
- DAt.TIMORE, MARYLAND 21?03 ~475 H r DE' ion m m na m x.tn February 28,1991 U. S. Nuclear Regulatory Commission Washington,DC 20555 ATFENTION:
Document Control Desk SUlMECT:
Calvert Cliffs Nuclear Power Plant Unit Nos.1 & 2: Docket Nos. 50 317 & 50 318 Annual Report of Failures and Challenges to PORVs and Safety Valves for Jhp Period of January 1.1990 through December 31. lWI Gentlemen:
This report is submitted in accordance with Technical Specification d9 i.5.c. One Power Operated Relief Valve (PORV) failure and three PORY actuations occurred in 19W).
On h1 arch 30,1990, during the performance of Surveillance Test Procedure M 572 B 1 (18 month periodicity), Unit 1 PORV RC.402 ERV failed to open. Subsequent investigative efforts revealed that a thermal overload contact for the solenoid supply breaker had opened sometime prior to the test. The contact was reshut and the test completed satisfactorily. A more detailed investigation of the event revealed excessive current was required by the solenoid to perform its function. This current exceeded the design value and was linked to a stuck roller on the solenoid. The excess friction forces caused by the roller prevented the solenoid slug from reaching its magnetic center, resulting in chatter and excess coil current. Over e short period of time, the excessive currw caused the supply breaker thermal overload contact to open. The cause was corrected and ottei PORVs inspected to prevent further occurrence. This event was reported in detailin Licensee Event Report 50 317NO 011.
On July 31,1990, Unit i PORY RC 404-ERV lifted while operating with hiinimum Pressurization Temperature (htPT) protection enabled. The plant was in h10DE 5 at a Reactor Coolant System (RCS) pressure of 209 psia. The h1PT enabled mode of operation provides overprc<sure protection at low plant temperatures by reducing the PORY relief setpoint to approximately 385 psia. This event occurred when a worker, performing maintenance in the hiain Control Board, mechanically agitated a 250 ohm resistor which converts the pressure transmitter signal to a D.C. control signal.
This caused an erroneous high pressure signal to be generated, resulting in the subsequent relief valve actuation. Upon closer investigation, the resistor was found to possess oxidized leads and had been improperly connected to its circuit (crimped connections vice soldered). The combined effects of the agitation and high resistance connceilons caused the generation of the erroneous signal. All other similar PORV controlloops were inspected and necessary repairs made.
On September 23,1990, Unit 1 PORY 11C-402 ERV lifted while operating with htPT protection enabled with the plant in htODE 3 at an RCS pressure of 330 psia. Subsequent investigation revealed no dermitive root cause. After discussion with the Assistant General Supervisor for Nuclear 9103040200 910228
/
PDR ADOCK 05000317
.2 R
- (g l
.. - ~... - - - - - - -. -.
Document Control Desk 4
February 28,1991
- Page 2 l
Operations, the decision was made to place the valve back into service and to monitor the instrument controlloop with a recorder.
On December 2,1990, Unit 1 PORY RC402 ERY lifted while the plant was operating with MPT protection enabled with the plant in MODE 3 at an RCS pressure of 375 psla. This valve itad actuated once before on September 23, 1990, at which time a decision was made to install an mstrument recorder prior to the next shutdown to monitor circuit response. The recorder traces indicated that the actuation of a control relay in the pressurizer level control system created a noisc signal which was impressed upon the MPT control loop for RC 402-ERV. Additional testing verified this finding, resulting in the redesign and correction of the pressurizer level controi circuits for both units. Retesting has shown that essentially all electrical noise generated by this circuit has been climinated.
Should you have any further questions regarding this matter, we will be pleased to discuss them with you.
M ry truly yours, RED /REIWjd cc:
D. A. Brunc, Esquire J. E. Silberg, Esquire R. A. Capra, NRC-D. O. McDanald, Jr., NRC T. T, Martin, NRC L. E. Iucholson, NRC R.1. McLean, DNR J 11. Walter, PSC
,