ML20009F788
| ML20009F788 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry, Arkansas Nuclear  |
| Issue date: | 07/16/1981 |
| From: | Dircks W NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | Pryor D SENATE |
| Shared Package | |
| ML20009F789 | List: |
| References | |
| NUDOCS 8108030013 | |
| Download: ML20009F788 (3) | |
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G. W. Kerr Docket Nos.53-259 ED0 Rdg L. Underwood 50-260 ORB #2 Rda E. Case 50-296 OELD H. Denton OCA (3)
S. Hanauer jut.16 E M. Bridgers (ED0-10576) R. Mattson Program Tupport Staff, NRR E: "ughes The Honorable David Pryor M. Stine T. Murley United StEtes Senate D. Eisenhut R. Vollmer Washington, D. C.
20510 J. Heltemes B. Snydcr T. Ippolito
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Dear Senator Pryor:
R. J. Clark
- I am writing in response to your letter of June 9,1981 regarding a conctituent's letter concerning incidents that occurred at the Browns Ferry Nuclear Plant, Unit No. 3, on May 22,1981 and at Arkansas Nuclear One., Unit No.1, on May 10,1980. A discussion of these incidents and the questions raised in Mr. Russ Lacewell's letter of May 29,1981 is enclosed.
l I hope that this satisfactorily responds to your request.
l Sincerely, (signed) T ^ #
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- NRC FORM 318 tlO,80) NRCM O240 OFFICIAL RECORD CO PY
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Incident at Browns Ferry Unit 3 - May 22, 1981 At 11:45 p.m. on May 21, 1981, the operators at Browns Ferry Unit 3 noted an l
increase in pressure in the primary containment structure surrounding the l
nuclear portion of the facility.
Shortly thereafter, the operators noted that water was filling the sump in the containment building, indicating a leak in the system. Based on the rise in water level in the sump, it was detennined that the leakage rate was 21.5 gallons per minute (gpm). At 12:35 a.m.
l on May 22, 1981, the reactor power level was reduced to 40% to investigate l
the leakage. When it was evident that the leakage was continuing, the reactor was shutdown at 1:23 a.m. and brought to a cold shutdown condition. When the reactor is at power, pressure in the system is nominally 1020 pounds per square inch absolute (psia). As the reactor was brought to a cold shutdown condition, the pressure in the system is reduced. By 2:00 p.m., the pressure was down to 25 to 30 psi (approximately the nonnal pressure in a household water system) and the leak rate was reduced to 7 gpm.
The Browns Ferry units are Boiling Water Reactors (BWRs). The license Technical Specifications require that prior to startup of these BWRs, the air in the containment structure surrounding the reactor systems must be removed (purged) and replaced with nitrogen, which is an inert gas. Since a person could not survive in such an atmosphere, it was necessary to purge the nitrogen gas from containment and replace it with a breatheable air atmosphere before maintenance personnel could enter the containment structure to repair the leak. This took about 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, during which time the leakage f.ontinued.
The venting or purging is a routine and necessary operation if maintenance work is required inside the containment structure. The purging (. venting) is authorized by the NRC within limits on the types, rates and amount of thdioactivity that may be released to the environment. These limits are incorporated in the Technical Specifications which are part of the license.
The radioactivity released as a result of the May 22, 1981 incident at Browns Ferry Unit No. 3 were well below the limits authorized in the Technical Specifications.
I In any power plant, packing is used in many valves to seal the space between the valve stem and valve body, while permitting the valve stem to turn.
Although the packing material is different, this is similar to the packing used in the valves and faucets in a household water system.
In a household system, this packing gradually becomes worn and has to be " tightened" (compressed) or replaced. At Browns Ferry Unit 3, the cause of the leake was a packing leak around the stem of a large 28" gate valve. Because of the high differential pressure, the leakage caused part of tne packing to blow out. Once the maintenance personnel were able to get into the containment structure, the leakage was closed off, the valve stem dressed and the packing replaced.
While the average leakage rate was relatively small (about 10 gpm), the total amount of water that leaked out of the system was about 17,500 gallons due to the length of time the leakage continued. The water collected in the containment sump was monitored, transferred to the radioactive waste processing system, purified by filter-demineralizers and returned to the system. There l
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l 1 was a very small amount of gaseous activity collected in the containraent structure as a result of the leak, primarily short-lived xenon-133 and xenon-135. The containment atmosphere monitoring (CAM) system measured a total gaseous activity of 1.2 x 10-4 uci/cc (0.00012 uci/cc) at 1:30 a.m.
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on March 22, 1981. The peak activity measured at 4:30 a.m. was 2.2 x 10-3 uci/cc. Gaseous iodine hvels were very low - just slightly above the levels normally present in containment. The nitrogen that was purged from contain-ment was processed through the deep charcoal bed filters and released from the 600 foot stack. The radiation monitors indicated that the radioactivity released from the steck a.s a result of the valve packing leak was hardly detectable compared to nonnal operations and was well below the releases authorized by NRC and the Environmental Protection Agency (EPA). At no time was there any hazard or any significant effect on public health and safety as a result of the leak.
I Incident at Arkansas Nuclear One - Unit 1 - May 10,1980 On May 10,1980, a reactor coolant pump seal on Arkansas Nuclear One Unit 1 (AN0-1) failed, releasing about 60,000 gallons of reactor coolant into the containment building and some gases to the containment atmosphere. The reactor operators were able to contain significant releases within the containment building.
In order to permit repair or replacement of the pump seal and return the plant to operation, it wds necessary to vent the contain-ment gases.
The resulting release was required to be conducted within the regulatory limits of 10 CFR Part 20. An assessment was done by Arkansas Power and Light that venting could be accomplished within those limits. Prior to the initiation of venting, the NRC evaluated the analysis of the content of the gases in the containment and the Arkansas Power proposal and agreed with the licensee that releases could be accomplished within regulatory limits.
Following this decision, Dr. Young of the Arkansas Department of Health had orally requested that Arkansas Power postpone the actual venting for 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> to permit the State to assess the situation. At no time did Dr. Young issue an order to the licensee to stop venting, nor did the State officiall.y express
= its views to the NRC that the licensee should delay. NRC did not learn '6f" the request until after it had approved the licensee decision based on its own analysis. Believing that there was no basis for delay, the NRC permitted verit;ng and that processing was completed on May 15, 1980.
During the venting process, repre'sentatives of the U. S. Environmental Protection
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Agency and the Arkansas Department of Health went to the site and checked the analysis of the gases being vented and assured themselves that such releases l
were within safety limits. Offsite monitoring by the U. S. Environmental Protection Agency and the licensee detected no measurable increase in radiation l
levels as a result of the venting. The coolant water was processed through the plant's installed cleanup system to be reused as reactor coolant and was not discharged to the environment. The State also eoutinely conducts environ-mental monitoring in the vicinity of the site, under a contract with the NRC.
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ACTION CONTROL DATES-CONTROL NO M* M$d D<
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SECY-81-0807 Logg.ng page _ 6/ll/8]
l NnC SECnETAnlAT TO:
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Gen. Counsel O
O Public Af fairs O Secretary incomino Senator David Pryor, Const Ref From: _
Huss Lacewell To:
OCA g,1, ___6/9/81
Subject:
re the accident at Browns Ferry 113 and7he release of radioactive water and gas O Prepare reply for signature of:
O cna,rman O comrn,ssione, _
O E DO. GC, CL, SOL, PA. SECY O signature niock omiirea O _.
O neturn originat of incoming with response XGX For direct reply.
Suspense: July 6 0 ror ann,ogriate action O ror intormation O ror recommenaation staf d di' ' }
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OCA to Ack um n.3r;y,,.e-
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- Cend three (3) copies of reply to Secy Mil Facility ACTTONLYP