ML20116H389
| ML20116H389 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 09/15/1992 |
| From: | Daley M NEW ENGLAND COALITION ON NUCLEAR POLLUTION |
| To: | Selin I NRC COMMISSION (OCM) |
| Shared Package | |
| ML20116H374 | List: |
| References | |
| NUDOCS 9211130106 | |
| Download: ML20116H389 (4) | |
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New Englant Coalition on Nuclear Pollution,Inc.
Box 545, Brattleboro, Vermont 05302 Phone (802) 257 0336 i
Septembec 15, 1992 Ivan Selin, Chairman U.S. Nuclear Regulatory Commission Washington, DC
Dear Chairman Selin:
Fe wish to alert you to a situation at the Vermont Yankee Nuclear Power Station that requires your immediate attention and corrective action.
Vermont Yankee routinely operates turbine uullding roof e.-
haust fans in contradiction of its Final Safety Analysis Report (FSAR).
This practice may have resulted in an in-adequately monitored release of radioactive materials (par-ticulate and gaseous) to the environment during an incident on January 13, 1992 (see the Feb. 21.'92.NRC inspection report No.50-271/92-01, hereafter NRC report,and Licensee Event Report LER 92-003: A0G RUPTURE DISC TEMPORARY REPAIR 4
NOT WITHIN SYSTEM DESIGN BASES Feb. 13,'92).
On Monday, January 13, 1992 at approximately 1:30 PM, with the reactor at 100% power, maintenance personnel _in-advertently shut off the Advanced Dif-Gas System (A0G) which caused a rapid build.up_of pressure-burating the-steam jet air ejector rupture disc and releasing' radioactive gases and-particles into the turbine building.
Because of poor design, the release from the rupture disc was not immediately contained.
Instead, the gases and par-ticles migrated throughout the tnrbine building'and-eventually into the' reactor building,: before apparently en-tering the plant exhaust.
-Because the plant was operating with leakyffuel, workers were needlessly _ exposed to radiation levels as high as 38%
of Maximum Pennissible Concentrations during this incident.
This-is the-second. fuel cycle in a. row that marwjement.has decided.to operate the plant with leaky fuel, a-practice in conflict with keeping radiation doses as low as reasonably achjevable.
In a July 1990 letter, plant 1 workers _ warned your Staff about this potentially dangerous condition at the plant.
Concentrations of radioactive gases and pa-ticles-in this uncontrolled release were at least ten times h.gher_-
than-they would have been-under normal. operating' conditions.
9211130206-921102 PDR COMMS NRCC CORRESPONDENCE'PDR
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NECNP-2 Counts per minutes at the r. tack went from a pre-event level of 250 cpm to 130,000 cpm (NRC report), indicating consider-able exhaust activity that by-passed the charcoal filter system and catalytic converter.
These systems are designed to reduce radiation levels of reactor off-gas by a factor of 10,000 before release to the environment.
In addition to this monitored and recognized release path-way, we suspect that significant amounts of the radioactive materials released from the steam jet air ejector rupture disc were vented directly to the environment through the un-filtered turbine building roof exhaust fans.
These exhaust-fans have no automatic emergency stop system to assure that this direct pathway is sealed during releases of this type (FSAR 10.12-4 and Fig 10.12).
Considering the close proximity of the plant to the Vernon Elementary school (within 540 yards), and the presence of particulates in the-release, it is surprising to find no discussion of this pathway in either NdC or Vermont Yankee reports.
Yet there is every reason to believe these fans were in op-eration during this incident.
Year-round operation has be-come common practice in recent years to reduce elevated levels of radioactive gases in the turbine building because of the leaky feel.
This practice contradicts the plant FSAR which indicates surtmer operation only.. Complaints from con-cerned workers had alerted Vermont Yankee management and your Staff to this questionable practice, as well as to the practice of leaving turbine building doors open in all sea-sons.
The turbine building exhaust fans are'a kuovn~pathwry for uncontrolled radioactive releases.
This pathway was the subject of considerable discussion 9 years ago_ in assocla-tion with contamination of Connecticut River sediment with co-60 (see Memo for Darrell Eisenhut-from Richard W.
Starostecki re: LOW LEVEL RADIOACTIVE EMISSIONS FROM BWR TURBINE ROOF VENTS 11/7/83).
Further, the NRC report notes particulate levels in.the.
reactor building higher than levels reasured in1the' turbine building where the release took place.
The buildings are divided by-airlocks and hava-separate ventilation systems.
Neither.NRC_nor Vermont Yankee. reports explain how the release. crossed the boundary between the buildings._ How-ever, in a past inc.ident freon released on the roof entered the control room air supply (LER 85-012-00: CONTROL _ ROOM HABITABILITY ~ SYSTEM ACTIVATION).
Did releases via the tur-bine_ building roof exhaust fans contaminate the reactor building intake air supply?
Vermont Yankee claims that the releases associated with this y
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NECNP-3 incident didn't exceed any limits (LER 92-003, NRC report).
We seriously question the reliability of this claim, given the nature of the release and the existence of the roof ex-haust pathway.
Specifically, were Radiation Protection or Health Physics personnel aware of the beyond-FSAR practice of operating the turbine building roof exhaust fans?
Did they adequately understand the probable flow paths of the release from the rupture disc?
Since particulates were in-volved, has 'lermont Yankee adequately assessed the long-term 1eaching of radioactivity off the roof and its effect on the environment and the public.
The NRC report notes only that "The surveys taken appear to be properly documented and of adequate detail to assess conditions withiD the plant." (em-phasis added).
Within six minutes of the discovery of the rupture, the A0G was restored to service and leakage out the ruptured disc was minimized by placing a metal bucket over it.
- However, the plant then continued operation for two days instead of immediately shutting down to repair the ruptured disc.
The steam jet air ejector rupture disc has burst many times in the past twenty years.
Until this incident, the plant has never continued to op wate or attempted on on-line repair.
Records from 19,3 demonstrate that the plant moved to shut down within 5-7 hours of discovery of a steam jet air ejector rupture disc rupture (Abnormal Occurrence Nos.
A0-73-27, A0-73-26.AO-73-25).
Yet, plant management deliberated for two days about-whether an on-line repair could be done, or if they could continue operations in a degraded mode (ie, with a bucket over the leak).
Meanwhile, control room operators were required to perform constant surveillance of the degraded A0G to prevent further uncontrolled releases (LER 92-003: A0G RUPTURE DISC-TEMPORARY REPAIR NOT WITHIN SYSTEM DESIGN BASES Feb.
13,'92).
We understand that management had decided it was possible to continue operations in the degraded mode until your Staff, L
in private consultation at Corporate Offices, forced manage-ment to take the plant off-line and-make repairs.
Given these facts and uncertainties, we feeA that Vermont l
Yankee operated in a manner that recklessly endangered workers, and represented a significant-increased risk to the E
public.
We require you to:
- 1. Determine why there was a two day delay in making. repairs and whether this was a violation of operating procedures i.7 F
-force at the time.
If so,1to identify those responsible and L
carry out disciplinary action.
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1 NECNP-4 2.
Conduct a public investigation of the release to determine the full extent of worker and public exposure, and to make available (with supporting documents):.
total curies-released, radia'=lon doses to workers and public including pathway analysis, and stack monitor data for the period just l
i before and twelve hours after the event,
- 3. Require Vermont Yankee to accelerate its. plans.to. isolate-all-turbine building e.shaust points and vent them into a.
l filtered and monitored system.
4.
Conduct a plant-wide design study to identify any other--
inadequately filtered and monitored pathways to the: environ-ment and require Vermont Yankee to correct these flaws.
We look fc mard-to-your prompt attention to-this situation.
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Sincemly, g'
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Michael J. D,aley for,r'/> Board of t.he Ne7 England Gyalition en. Nuclear Pollution
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cc. Vermont Yankee Governor Howard Dean media i
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