ML19271A580
| ML19271A580 | |
| Person / Time | |
|---|---|
| Issue date: | 02/26/1980 |
| From: | Harold Denton Office of Nuclear Reactor Regulation |
| To: | Haller N NRC OFFICE OF MANAGEMENT AND PROGRAM ANALYSIS (MPA) |
| Shared Package | |
| ML19271A581 | List: |
| References | |
| NUDOCS 8003250855 | |
| Download: ML19271A580 (4) | |
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s PO ORANDUM FORf Nonnan M. Haller'. Ofrector
. 0ffice of Management and Program Analysis e
Harold R. Denton, Director F10M: '
Offics of Nuclear Reactor Regulation
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SUBJECT:
- ASNORMpt 0CCURRENCE REPORT TO CONGRESS FOR
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,. : FOURTH QUARTER CT-1979
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Your memorandum of February 8.1900 requests MRR review and consent on the subject draft report,.
f NRR concurs with issuing the proposed draft report to Congress on Abnonnal Occurrences October - December,1979. NRR coeunents (marked up pages of thedraftreport)areattached.
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Orip 31 tigned by E. G. Case arold R. Denton Director
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Enclosure:
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FEBRUARY 2 6 !S80 MEMORANDUM FOR:
Norman M. Haller, Director Office of Management and Program Analysis FROM:
Harold R. Denton, Director Office of Nuclear Reactor Regulation
SUBJECT:
ABNORMAL OCCURRENCE REPORT TO CONGRESS FOR F0l!RTH QUARTER CY-1979 Your memorandum of February 8,1980 requests NRR review and coment on the subject draft report.
NRR concurs with issuing the proposed draft report to Congress on Abnormal Occurrences October - December,1979. NRR comments (marked up pages of the draft report) are attached.
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Harold R. Denton, Director Office of Nuclear Reactor Regulation
Enclosure:
As Stated
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On October 26, 1979, the NRC sent a Notice of Violation and Notice cf Proposed Imposition of Civil Penalties (55,000) to the licensee, identifying the incident as an item of noncompliance associated with the licensee's implementation of his physical security program.
Although this event constituted an item of noncompliance with the implemen-tation of the licensee's physical security program, it is not proposed to include it as an abnormal occurrence because the unauthorized person was contained within the sleeper cab during the 1-1/4 hours he remained undetected.
In addition, during the e'1 tire period, the tractor / sleeper unit was controlled by an armed security guard who was sitting in the cab, and who maintained constant visual acuity of the vehicle and area contiguous to it.
Upon dis-covery of the unauthorized individual, the plant security escorted the unauthori:ed individual to the main gate.
2.
Loss of Nonsafetv-Related Reactor Coolant Svstem Instrumentation Durin Ooeration
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At 3:15 p.m. on NovemDer 10 with Unit 3 of the Oconee Station at 100 percent power, the main condensate pumps tripped, apparently as a result of a technician performing maintenance on tne hotwell level control system.
This led to reduced feedwater flow to the steam generators, which resulted in a high reactor coolant system (RCS) pressure reactor trip and simultaneous turbine trip at 3:16:57 p.m.
At 3:17:15 p.m., the inverter power supply, nonsafety-related, feeding all power to the integrated control system (ICS) tripped and failed to automatically transfer its loads from the DC power source to the regulated AC power source.
The inverter had tripped due to blown fuses, resulting in loss of RCS indicators and recorders in the control room, except one wide range RCS pressure recorder-This condition existed for approximately 3 minutes, until an operator could reacn the ecuipment room and switch the inverter manually to the regulated AC As a result of the power failure to the ICS, all valves controlled by source.
the system assumed their respective fail positions.
This resulted in a coolcown of the RCS to 1635 psi and 530*F.
The operator, expecting this condition, startec all makeus pumps and opened the associated high pressure injection valves to the RCS which limited the rate of RCS pressure reduction and asso-ciated reduction in pressurizer level.
At 3:20: 42 p.m.,
power was restored to the ICS and RCS conditions were restored.
Although RCS cooldown limits were exceeded, the pressurizer and steam generators dic no. go cry, and at least 79*F subcooling was maintainea during this event.
No engineered safety features actuation setooints were reached and, except f;r the components discussec aoove, no component malfunc. ions occurred.
In accition. the oce ator resconcec in an appropriate manner.
Therefore, there was no impact on puolic healtn or safety.
The licensee has insta' led a reduncant e'ectromecnanical transfer switch Set-een :ne icacs anc rar ' n : r 'f This switcn will actuate and
- c-e-the loacs from.ne egulatec se:c:y shouic the original static switch fail :: transfer-
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n-Longer term resolution of the need or desirability to separate these instru-ments onto diverse electrical supplies or to provide redundant instrumentation alsplay channels for operator use from essential power supplies are also under consideration.
IE Information Notice No. 79-29 was issued on November 16, 1979 to all power reactor facilities holding licenses and construction permits informing them of he event and stating that the information should be disseminated to all operational personnel.
3.
Oce-atier wit 5out Primary Containment Intecrity At c:45 a.m. on December 6,1979, Browns Ferry Unit 3 was taken critical sub-secuent to a re'ue'ing outage.
On December 8. the licensee experienced dif ficulty in establishing the required drywell-to-torus cif ferential pressure anc nigh nitrogen makeu; to the prima y containment curing an approach to full power.
On December 9, the cause of the difficulty was identified as a leaking primary containment equipment hatch with three improperly torqued bolts.
The prcclem -as promptly correctec.
The hatch leakage was reported to the resident inspector on December 10, as approximately 12 tires the Technical Specification allowance.
This hatch had previously passed a local leak rate test and the containment passed an integrated leak rate test in November 1979.
The reactor hac returned to operation on December 6 from a ref eling outage and had operatec at power levels of less than 25% during Decemoer 6 through 9.
Uoon ciscove y of the leaking hatch, the bolts were promotly retightened and a local leakage test performec witn satisfactory results.
A supervisor and an inspector from the NRC Region II Office arrived on site December 10 and, with the NRC resident ins 0ector conducted an inspection on this matter from December 10 througn December 14, 1979.
Two Confirmation of Action letters were issued by the Region II Office, December 12 and 21, outlining corrective measures and actions to be taken by the licensee.
These actions inclucec a formal investigation of events whicn resulted in the loss of containment integrity: verifying current nitrogen consumption rates on all three Browns Ferry units; reviewing the M equacy of management controls on clant maintenance activities.nat impact or. plant safety; reviewing procedures for prompt reporting to NRC of plant events; and verifying proper closure anc satisfactory leak rate tests or' equipment natches of all three units.
IE :nformation Notice No. 79-33 was issuec to all licensees on December 21 cescri ing this event.
A notice of procesed imposition of a civil penalty anc ar order were issuec to TVA or January 4, 1980.
On January 10, 1980, TVA paid ci "' :enaities in the am unt of S'9. ::.
ne cause of this event as a breaxcowr. in management anc procecural controls
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'- ne areas of mainter.ance. Diant opera-ions anc reporting.
However, no raciat on releases occurrec during tne time per'od anc a natch leakage of tnis ag-. ace as arti<e( *o go uncetec.ec fo* a long pe-ioc of time due to the 9ig n'trogea makeuo
- .c :ne containment.
Therefore, there was no actual it:ac. on puolic nealin or safety.
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