ML20134F074
| ML20134F074 | |
| Person / Time | |
|---|---|
| Issue date: | 10/31/1996 |
| From: | Chaffee A NRC (Affiliation Not Assigned) |
| To: | Shirley N GENERAL ELECTRIC CO. |
| References | |
| NUDOCS 9611040258 | |
| Download: ML20134F074 (4) | |
Text
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&tober 31,1996 Mr. Noel Shirley, M/C187 General Electric Company 175 Curtner Avenue San Jose, California 95125
SUBJECT:
REQUEST FOR A TECHNICAL REVIEW 0F A DRAFT INFORMATION NOTICE ON THE POTENTIAL FAILURE OF THE INSTANTANE0US TRIP FUNCTION OF GE RMS-9 PROGRAMMERS l
Dear Mr. Shirley:
I l
The U.S. Nuclear Regulatory Comission (NRC) is planning to issue an
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l information notice on the potential failure of the instantaneous trip function of some GE RMS-9 programers. We ask that you review the enclosed draft of 1
that information notice to ensure the technical information is accurate.
Your l
cooperation in this matter is appreciated.
Please return any comments you may I
have as soon as possible. A copy of this request and your response will be l
placed in the Public Document Room for review by the public.
Your response should be mailed to:
U.S. Nuclear Regulatory Comission l
Division of Reactor Program Management ATTN:
David Skeen, NRR/PECB MAIL STOP: 011E4 Washington, DC 20555-0001 Please address any questions you may have on this matter to David Skeen of my l
staff. Mr. Skeen may be reached by phone (301) 415-1174 or you may fax coments to (301) 415-2279.
If no comments are received by close of business November 4,1996, we will assume the technical information in the notice is correct.
Sincerely, l
[Originalsignedby]
Alfred E. Chaffee, Chief Events Assessment and Generic Communications Branch Division of Reactor Program Management Office of Nuclear Reactor Regulation
Enclosure:
Draft Information Notice l
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E, DRAFTi UNITED STATES NUCLEAR REGULATORY COMMISSION i
0FFICE OF NUCLEAR REACTOR REGULATION 1
WASHINGTON. D.C.
20555-0001 l
November xx. 1996 l
l
.NRC INFORMATION NOTICE 96-XX: POTENTIAL FAILURE OF THE INSTANTANE0US TRIP FUNCTION OF GENERAL ELECTRIC RMS-9 PROGRAMMERS l
Addressees All holders of operating licenses and construction permits for nuclear power l
plants.
Purcose The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alert addressees to the potential that the instantaneous trip function of some General Electric RMS-9 overcurrent trip device programmers may fail to trip the associated 480-V ac circuit breaker at the desired current setting.
It is expected that recipients will review the information for applicability to their facilities and consider actions, as appropriate, to avoid similar problems.
However, suggestions contained in this information i
notice are not NRC requirements; therefore, no specific action or written response is required.
Descriotion of Circumstances General Electric Nuclear Energy (GE-NE) sent the results of an evaluation of some reported failures of the instantaneous trip function of GE Type RMS-9 Overcurrent Trip Device Programmers to all affected customers and the NRC in a letter dated August 30, 1996. These devices were provided as spare
) arts, or as components of eu.her refurbished GE Type AK 480-V ac circuit brea(ers or new AK/AKR-7 circuit breakers for overcurrent protection. The affected programmers may trip at an instantaneous current value below the selected setting.
The devices were manufactured by GE Electrical Distribution and Control and supplied by GE-NE as safety-related components for balance-of-plant and unspecified applications.
Since the specific applications and associated safety functions of the RMS-9 programmers are not known to GE-NE. the company notified affected licensees in accordance with 10 CFR 21.21(b).
- However, because some licensees may have purchased these devices as commercial-grade items or from a dedicating entity other than GE-NE. the NRC is issuing this information notice to ensure that all potentially affected licensees are i
- notified, i
l
j IN 96-XX 4
November xx. 1996 i
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Page 2 of 3 Discussion The cause' of the failure of the instantaneous trip function was determined to be a polyester epoxy film on the internal switch contacts. The film acts as J
an insulator, so that if the instantaneous switch setting is changed from its initial setting, the contacts do not make and the programmer automatically fails to its lowest instantaneous )ickup setting (1.5X).
The film is the j
result of insufficient curing of tie conformal coating (polyester epoxy) a) plied to the RMS-9 programmer during final assembly.
Testing by GE showed tlat some of the coating ran under the switch during application and the i
coating was not properly cured because it was masked by the switch during the ultraviolet curing process.
Over time, the external switch contacts acted as wicks and drew some of the uncured coating into the switch where it formed a thin film on the internal switch contacts.
Testing by GE also showed that the film did not form between the movable contacts and the stationary contacts in the switch.
Therefore, if the instantaneous trip function is operating properly and the switch has not been moved from its initial position, it should continue to operate properly.
An RMS-9 programmer that trips at a value lower than the selected value could cause a motor to fail to start because the starting current could be higher than the setpoint in the programmer. -If a programmer trips at higher than expected value, it is possible that the breaker may not trip soon enough under fault conditions and other breakers upstream may have to trip to clear the fault, resulting in the loss of more of the power system than anticipated.
However, no reported failures of the type discussed herein have resulted in a breaker tripping at a current higher than the desired setting.
Related Generic Communications NRC Information Notice 93-75, " Spurious Tripping of Low-Voltage Power Circuit Breakers With GE RMS-9 Digital Trip Units." was issued on September 17, 1993.
to alert licensees to the potential for. the RMS-9 programmers to cause spurious circuit breaker trips when exposed to short duration (100 microseconds) current spikes (high-frequency electrical noise).
Although the same component is involved in both instances, the two problems are unrelated.
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l-DRAFTi svnd;xx.1996 Page 3 of 3 This information notice requires no specific action or written response.
If you have any questions about the information in this notice, please contact one of the technical contacts listed below or the appropriate Office of Nuclear Reactor Regulation (NRR) project manager.
Thomas T. Martin Director Division of Reactor Program Management Office of Nuclear Reactor Regulation Technical contacts:
Stephen D. Alexander NRR (301) 415-2995 E-mail: sda@nrc. gov David L. Skeen. NRR (301) 415-1174 E-mail: dis @nrc. gov
Attachment:
List of Recently Issued NRC Information Notices l
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