ML20147D214
| ML20147D214 | |
| Person / Time | |
|---|---|
| Site: | Vallecitos File:GEH Hitachi icon.png |
| Issue date: | 11/10/1977 |
| From: | Eisenhut D Office of Nuclear Reactor Regulation |
| To: | Goller K Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7812190178 | |
| Download: ML20147D214 (4) | |
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UNITED STATES
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y .. 4 NUCLEAR REGULATORY COMMISSION j 'I I WASHINGTON, D. C, 20555
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...# NOV 101977
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E$0RANDUMFOR: K. R. Goller, Assistant Director for Operating Reactors, DOR FROM: D. G. Eisenhut, Assistant Director for Operational Technology, 00R
SUBJECT:
PROPOSED SECTION 208 ABNORMAL OCCURRENCE EVENT -
GENERAL ELECTRIC TEST REACTOR After several discussions with OMIPC, we have determined that the recent events related to the shutdown of the General Electric Test Reactor meet the criteria for reporting the event as an Abnorm 1al Occurrence. Specifi-cally, the events constitute the discovery of a major condition not specifically considered in the Safety Analysis Report which reouired immediate remedial action. ,
1 We request that you provide a proposed Federal Register Notice for this event to this Office by COB November 16, 1977. Utilizing your input, we will coordinate further actions related to the reporting of this event with OMIPC.
A copy of a Federal Register Notice for a previously reported Abnornal Occurrence is enclosed for your information.
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j D. G. Eisenhut, Assinant Director for Operational Technology Division of Operating Reactors
Enclosure:
As stated 7812190f78 Pi
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Caus or Causes - The cause of the breach of the security system was the failure f tne personnel on duty to comply with security directives for '
the contro of access to the protected and vital areas of the plant.
Actions Taken : Prevent Recurrence Licensee - The lic ee reviewed the adequacy of the existing secu Fagram y pian. Additional measu s were taken to strengthen the security through personnel instruc. n, monitoring for enforcement, aut# ting and increased security staffh at security stations durin periods of heavy personnel traffic.
NRC - NRC expressed its concern abouw the seriouc ature of this type of security breakdown and identified th' acti deemed necessary to correct tne situation during the inspectio as well as at a special corporate meeting on April 22 in Denver 01 do. Enforcement action also included a proposed civil penale in the a unt of eignt thousand dolices.
Following comp ietion of a et ' making proceeding address to uograding of physical s_curity rec ements at all nuclear power plants, the NRC issued revised physic ' security regulations (10 CFR 73.55) 1 February 1977 which require . ore stringent security measures to be implee nted at this plant and e ner nuclear pcwer plants.
During th pericd May 17-24, 1977, inspectors verified that corrective actione nad been implemented.
ture reports will be made as aporopriate, s 77-3 Fuel Rod Failures at Nuclear Power Reactor Preliminary information pertaining to this event was reported in the Federal Register (42 FR 36897) on July 18, 1977. \
Date and Place - Cn May 15, 1977, during refueling coeraticns at Dairy-land Power Cooperative's Lacrosse Soiling Water Reactor (LAC 5WR) located in Vernen County, Wisconsin, the licensee noted that 3 of the 72 fuel assemblies in the core had localized fuel rod failures with portiens of -
the fuel rods within the assembly missing. A total of 26 of the 72 fuel assemolies exhibited some degree of fuel degradation.
Nature and Probable Consecuences_- The nuclear steam supply system of l LAC 3WR, a 165 megawatt (tnermal) plant, was provided by Allis Chalmers.
The LACBWR is the only operating boiling water power reactor ahich utilizes fuel rods with stainless steel cladding. Each fuel rod consists of uranium-dioxide fuel pellets housed in a closed hollow tube of stainless
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steel about 0.4 inches in diameter and about 8 feet long. The tube, or d
fuel clauding, is one of the several barriers designed to contain the radioactive fission products produced during reactor operation. Failure of fuel cladding causes the release of radioactive fission products into the reactor coolant which generally results in an increase in environ-mental releases above normally expected levels. Fuel clad failures can ,
vary in degree ' rom small perforations in the clad material to fuel rod !
failures. Fuel "od failures are a safety concern due to the potential l for affecting adjacent fuel rods or control rods and for affecting the l course of events in postulated accidents. Howevar, the limiting conditions l for plant perfornance are such that plant operation is conservatively l restricted before a safety problem develops or environmental radioactive l
releases become a safety concern.
For approximately a five-month period prior to reactor shutdown for the current refueling outage, the reactor was operated at reduced power levels in order to maintain radioactivity releases to the environs within the prescribed limits for reactor operation.
During refueling operations following reactor shutdown at the completion of Fuel Cycle No. 4, portions of fuel rods were found to be missing from three fuel assemblies (each assembly contains 100 fuel rods in a 10 x 10 array). Visual inspections resulted in the identification of def ective fuel rods in six fuel rod assemblies with an average of 4 to 5 defective rods per assembly. Three of these assemblies were observed to have some sections of fuel rod missing. An approximate total of 55 inches (length) of fuel rod was missing representing parts of 7 fuel rods. Subsequently, several of the missing rod pieces were recovered from the top of adjacent fuel assemblies in the reactor core and another piece was recovered in the spent fuel storage pool . In addition to the 6 fuel assemblies which exhibited visual damage, 20 fuel assemblies were found to exhibit fission gas release rates above soecified limits based on the results of fuel
" sipping" examinations which measure fuel assembly radioactive releases i to core cooling water.
The average exposure of the 26 damaged fuel assemblies is greater than l 16,000 megawatt days per metric ton of uranium. This is the highest average ,
exposure of discharged fuel in the history of LACSWR's operation. l Although this event is not the first incidence of fuel rod failures at i LACBWR, the extent and degree of the previous failures were significantly '
less than for this occurrence.
The precise nature of the significance to public health of this type event ,
can vary from no effect to a health hazard if consequent occupational l overexposures or large uncontrolled radioactivity releases occur. ~he l consequences of this event were a reduction in electrical generating l capacity, increased radiation levels in the reactor coolant and various other areas at the plant, and a possible extended refueling outage to
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- .- ! , i evaluate the extent of fuel damage and to recover missing pieces of fuel and cladding located within the reactor vessel . There were no personnel exposures to radiation and no radioactive releases to the environs in excess of regulatory limits as a result of this occurrence. No health hazards resulted.
Cause or Causes - Based on preliminary investigations, observed defects in the cladding of the damaged fuel rods are quite similar to the circumferential cracks observed in previous fuel inspections at LACBWR.
However, the longitudinal failures evidenced in fuel rods of the three most severely affected fuel assemblies appear to have been caused by a ccmbination of fuel / clad interaction and accelerated stress corrosion cracking. The intersections of the icngitudinal cracks and the circumferential cracks resulted in losses of complete sections of the cladding.
Actions Taken to prevent Recurrence Licensee - The licer.see is continuing to inspect the damaged fuel and to cetermine the cause of fuel rod failures. The specific actions to prevent recurrence will be determined based on the results of these investigations.
NRC - The NRC is reviewing the licensee's findings and, prior to 3 granting the licensee authorization to return the reactor to power operatien, will establish appropriate operating restrictions to prevent similar fuel rod failures in the future.
Future reports will be made as appropriate.
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FUEL CYCLE FACIL:T:C0 (Other Than Nuclear Power Plants) abnormal occurrences at fuel cycle facilities d ng this There wer period.
THER NRC LICENSEES .
(Industrial Radiographe Medica ns ti tu tions ,
Industrial User , c.) .
There are currently more than S,00 CRC nuclear m ial licanses in effect in the medical, in the United States, principal for use of radioisotw industrial and academic fie .
Incidents were reported in . 's category from licensees such as r ographers, medical institutions, and a coact material users.
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