ML20115A239
| ML20115A239 | |
| Person / Time | |
|---|---|
| Site: | 05000000, Arkansas Nuclear |
| Issue date: | 07/02/1984 |
| From: | Jordan E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| To: | Stello V Committee To Review Generic Requirements |
| Shared Package | |
| ML20114G054 | List:
|
| References | |
| FOIA-84-616 NUDOCS 8407100084 | |
| Download: ML20115A239 (2) | |
Text
_
.W JUL 0 21984 J
MEMORANDUMFORY Victor Stello, Jr.
Chairman Committee to Review Generic Requirements FROM:
Edward L. Jordan, Director Division of Emergency Preparedness and Engineering Response Office of Inspection and Enforcement
SUBJECT:
FAILURE TO TRIP OF A GENERAL ELECTRIC TYPE AK-2-25 REACTOR TRIP BREAKER AT ARKANSAS NUCLEAR ONE, UNIT 1 (ANO-1)
This is to inform you and the Committee of a recent complete failure of a reactor trip breaker (RTB) to open when.its undervoltage trip attachment (UVTA) was deenergized.
This failure to trip occurred at the ANO-1 plant on June 27, 1984 while the plant was undergoing its semi-annual RTB maintenance and surveillance program.
As described below, this event reinforces our conviction that the RTB bulletin being reviewed by the Committee should be issued.
Before describing the particulars of the event, I believe that three salient features of the ANO-1 RTB system should be brought to your attention:
(1) ANO-1 is the only known B&W designed facility that has an operational shunt trip -
device that automatically trips its RTB upon a valid trip signal; (2) ANO-1
~
has the capability to test independently the shunt trip and undervoltage trip functions of the RT8s; and (3) ANO-1 is one of the few operational B&W or C-E designed PWR facilities that routinely tests the response times of RTBs as found, in situ.
Because of the information afforded by this last, feature and the subsequent responses of the failed RTB, our views on issuing the RTB bulletin have been reinforced.
e The complete failure to trip was detected by an I&C technician while he was testing the UVTA function of TCB-3 in situ and in an as found condition.
This test is performed by manipulating a spring return to neutral test switch that deenerg.izes the UVTA when held in the actuate position and which, upon releasing the switch, actuates the shunt trip function.
After noticing that the RTB had falled to trip, and that the malfunction was not merely a delayed trip, the I&C technician summoned for assistance.
In so doing, he released the trip switch which, in turn, caused the breaker to trip by actuating the shunt trip device.
After the breaker had been tripped by the shunt device, it was removed from its cubicle and bench tested.
While being bench tested,'the UVTA failure could not be duplicated.
In fact, the breaker repeatedly tripped in the 40 millisecond range.while being actuated by the UVTA.
Further, the torque requir-t ed to trip the breaker was measured as being 12 ounce-inches whereas the acceptance criterion for tripping torque is 24 ounce-inches or less.
This event clearly demonstrates the effect of preconditioning a breaker caused by pe'~
k 1I 1
so Victor Stello. an initial trip prior to testing.
In this regard, it should be noted that most RIB tests presently being conducted on B&W and C-E designed plants are performed-after the breaker has been tripped.
As a result, such tests would tend to mask the true condicion of an as found RTB.
In contrast, the test method recomended by the bulletin would eliminate this test deficiency such that we would have more reliable information on which to base future NRC actions.
Further, this event was not reported to the NRC via a 50.72 notification.
The bulletin will ensure consistent prompt reporting of all RTB failures.
/ 'M p a AV C
- y Edward L. Jor an, Director Division of Emergency Preparedness and Engineering Response Office of Inspection and Enforcement cc:
R. C. DeYoung, IE J. M. Taylor, IE W.S.Schwink,ED0(15)
D. G. Eisenhut, NRR F. J. Miraglia., NRR G. Holahan,NRR T.' P. Speis, NRR A. C.*Thadani, NRR R. L. Baer, IE
- See previous concurrence i
~
- !E:0EPER
- IE:0EPER
- IE:0EPER:00
- !E:DEPER:0 IVillaiva ERossi SSchwartz EJordan 6/ /84 6/ /84 6/ /84 6/ /84 I
k