ML17252A784
| ML17252A784 | |
| Person / Time | |
|---|---|
| Site: | Dresden  (DPR-019, DPR-025) |
| Issue date: | 04/03/1975 |
| From: | Stephenson B Commonwealth Edison Co |
| To: | James Keppler NRC/RGN-III |
| References | |
| BBS 229-75 | |
| Download: ML17252A784 (2) | |
Text
CommonwE'~ Edison One First Natio-laza. Chicago, Illinois Address Reply to: Post Office Box 767 Chicago, Illinois 60690 BBS LTR. #229-75 Dresden.Nuclear R. R. #1 Morris, Illinois April 3, 1975 Power Station
SUBJECT:
REPORT OF UNUSUAL EVEN"T PER SOCTION 6.6.C OF THE TOCHNICAL SPECIFICATIONS THERMAL TRIP OF LPCI VP.>}-..VE 3-1501-SA"
Reference:
- 1. Regulatory Guide 1.16 Rev. 1 Appendix A
- 2.
P & ID Drawing M3(5o
- 3. Incident Reports 50-249/1975-18, 17, and 16.
Report Dates April 3, 1975 Occurrence Dates March 4, 1975 Facility: Dresden Nuclear Power Station, Morris, Illinois CONDITIONS PRIOR TO OCCURRENCE Pribr to thermal trip of LPCI valve 3-1501-SA the unit was in the "run" mode with thermal power at 1250 megawatts. Electrical load at.the time of the occurrance was 410 megawatts.
DF.SCRIPl'ION OF OCCURRENCE On March 4, 1975 at about 0230 hours0.00266 days <br />0.0639 hours <br />3.80291e-4 weeks <br />8.7515e-5 months <br /> LPCI valve 3-1501-SA experienced a thermal trip a~er going closed. The trip occurred while LPCI surveillance testing was in progress. Following the trips attempta*were made to open the valve without success for two minutes.
- After a two minute period, the thermal overload automatically reset and the valve opened without a thermal trip.
DESIGNATION OF APPARENT*CAUSE OF OCCURRENCE On investigation it was determined that the valve motor for the ~1501-5A valve was drawing about 3.5 amps during normal operation. The motor full load current is rated at 2.9 amps. It was further discovered that th~Sf is rated at 1 5 ft. lbs. torque which is the same as the motor for the
.April 3, 1975 3-1402-4A & B valve of the core spray system. The 3-1402-4A &: B valves are presently under investigation due to a similiar failure of the valve motors.
(Incident Reports 50-249/1975-18, 17, and 16) *
.ANALYSIS OF OCCURRENCE The failure of the 3-1501-5A valve to close did not place the safety* of the
- plant or public in jeopardy. The 3-1501-5A valve is normally in the open position during operation. Failure of the valve to close would not have hampered the design function of the LPCI system.
COmID:TIVE ACTION No immediate corrective action was required because.the valve was returned to the open.position, which is the safe position. Additional corrective action required that all the 3-1501-5 valves be placed in the open position*while opera-tingo Also; two new 15 :rt. lbs motors have been ordered to replace ll\\Qtors on the 3-1402-4A and 4B valves of core spray which exhibit the same type of failures. Following the deli very of the motors a test will be made with the new.
motors to determine the cause of the problem.
During the 1975 refueling outage which is scheduled for April 30, 1975 the 3-1402-4A valve will be disassembled and inspected. The results of this inspection will also help in determining the cause of the problem *.
FAILURE DATA Thia is the first time a failure has been noted of this type on the 3-1501-SA valve. Howe.. ~er, the Core Spray valves 3-1402-4A and B are presently under investigation for a similar problem.
BBS :TEL: smp File/NRC