ML20212G523
| ML20212G523 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 09/15/1997 |
| From: | Lochbaum D UNION OF CONCERNED SCIENTISTS |
| To: | Collins S NRC (Affiliation Not Assigned) |
| Shared Package | |
| ML20212G518 | List: |
| References | |
| 50-271-97-201, NUDOCS 9711060216 | |
| Download: ML20212G523 (4) | |
Text
I UNION OF CONCERNED SCIENTISTS September 15,1997 Mr. Samuel J. Collins, Director Office of Nuclear Reactor Regulation United States Nuclear Regulatory Commission Washington, DC 20555 0001 -
SUDJECT:
VERMONT YANKEE DESIGN INSPECTION REPORT NO. 50-271/97 201
~.
Dear Mr.' Collins:
By letter dated August 27,1997, the NRC staff transmitted the subject inspection report to the Vermont Yankee licensee. He transmittal letter states that "the design engineers of the Yankee Atomic Electric Company, who provided engineering services to VY, had excellent knowledge and capabilities" and that "tl e team concluded that it was unlikely that [Vennont Yankee personnel] would have uncovered some of the issues identified in this report." Dese conclusions seem contradictory, unless the NRC employs a relatively low standard of excellence. One would hope that a licensee supported by an excellent nuclear engineering organization would be able to uncover virtually every safety issue. Being unable to uncover some nuclear safety issues sbculd disqualify anyone from receiving excellent marks.
UCS reviewed the subject inspection report and identified three concerns regarding the safe operation of the facility. These concerns, detailed on the attachment to this letter, are summarized as follows:
He inspection team identiSed a potential single failure which prevents cooling water flow to both emergency diesel generators. He licensee's reported corrective actions reduced, but did not climinate, the probability of this failure, nis single failure, in conjunction with a simple loss of offsite power event, places the plant into a station blackout condition degraded by the probable l
catastrophic failure of both emergency diesel generators from overheating. His station blackout may last si;miscantly longer than evaluated tsy the licensee due to the extended unavailability of tu, emergency suelgenerators.
ne inspection team identified a problem with inadequate minimum flow protection for the residual l
heat removal (RHR) pumps. This design deficiency represents the potential for the common nede failure of all four RHR pumps following a postulated loss of coolant accident (LOCA). Since a LOCA is a design bases event and the plant's minimum licensing basis requires at least one RIM l
pump to mitigate the consequences of a LOCA, this unresohtd problem has considerable safety significance.
The inspection team also identified a problem with how the licensee accounted for loop uncertainty for the RHR LPCI flow instrumentation. Although the specific plant configuration is not defined in the inspection report, it appears likely that the RHR LPCI flow testing performed each refueling outage does not properly account for loop uncertainty.
Washington Office: 1816 P Street NW Suite 310
- Washington, DC 200381495 ' 102 332 0900
- FAX: 202 332 0905 i
Cambridge Headquarters: Two Brattle Square
- Cambridge. MA 02238 9105
- 6' N 147 5552 FAX: 617 864 9405 Cahfornia Office: 2397 Shattuck Avenue Suite 203
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- bte $431872
- FAX: 510-843-3785 i
9711060216 971028 PDR ADOCK 05000271 H
i September 15,1997 Page 2 of 3 i
i nis desip inspection focused on the residual heat removal system's low pressure coolant lehetion function and the systems required supporting this fbaction. De team found a number of operability i design bases problems, and failures by the licensee to propctly assess adverse conditions. De mWon these findings are symptomatic of programmatic weaknesses. Dus, it is more reasonable to suspect that comparable problems exist in other safety systems at this plant than it is to astume that these are isolated
[
events.
his inspection team's report also has serious implications with respect to this licensee's response to the NRC's request for information pursuant to 10 CFR 50.54(f) regarding adequacy and availability of dosip bases information. Als inspection team's many findings demonstrate that gly bases information was inadequate or unavailable or both. Even more disturbing, however, is the inspection team's conclusior. that thl licensee would have been imlikely to uncover some of these problems. his staff determination, com afar this licensee responded under oath to the 50.54(f) request, would seemingly leave the NRC staff without adequate assurance that "the configuration of[the Vermont Yankee fhcility) is consistent with the desip bases." In the letter transmitting this inspection report to the licacies, Mr. Stuart A. Richards stated, "we understand that your staff will be re examining your dosip bases program. Region l intends to review this issue when they inspect the findings in this report," UCS requerts that the NRC staff, either Region I or NRR, determine if the findings of this inspection are consistent with the licensee's sworn statement cS the availability and adequacy of design bas:s information.
UCS's review of this inspection report was conducted at the request of the Citizens Awarenees Network (CAN). We respectfbily ask that the NRC consider these commenu ami concems to be submit'adjointly by UCS and CAN. If there are any questions or comments regarding this matter, please contact me at (202) 332 0900.
Sincerely, (14010 W
David A.WhMm Nuclear Safety Engineer
Attachment:
as stated
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September 15,1997 Page 3 of 3 cc:
Mr. Jonathan M. Block, Esq.
Main Street P.O. Box 566 Putney, VT 05346 0566 Ms. Deborah B. Katz Citizens Awareness Network Box 23
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Shelburne Falls, MA 017..s
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Mr. David B. M:tthews, Chief Oerwric Issues & Enviroomental Projed: Brasch Omce ofNuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washiagton, DC 20555-000i Mr. Donald A. Reid Senior Vice President, Opernikus Vermont Yankes Nuclear Power Corporation Ferry Read Brattlebc,m, VT 05301 Mr. Stuart A. Richards, Chief SpecirlInspection Branch.
Omce of Nuclear Reactor Regulation U.S. Nuchiar Regulator / Cortunission Washingtm DC 20555-0001 Mr. Richard P. Sedano, Commissioner Vermont Department of Public Senice 120 State Street, f Floor Montpelier, VT 05602
(
Chairman, Board of Selectmen Town of Vernon P,0. Box 116 Vemon, Yr 05354 0116
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Attachment to UCS Letter en Vermont Yankee Der!gn Inspection Report 50 271/97 201
- 1. Section El.l.2.2(c) on page 5 of the report describes the team's Anding that the licensee was non.
conservatively testing LPCI flow rate. The report indicates that the licensee's safety analysis assumed a LPCI flow rate of 7450 gpm, whereas the acceptable test flow using recorder FR.143 could be as low as 7300 spm. Section El.3.3.2(D) on page 23 of the r6 port indicates that the RHR/LPCI Sow instrument has a loop uncertainty of +4.1W.5.6% of scale (20,000 spm). If this uncertainty is applicable to the flow instrument used for testing LPCI flow (presumably recorder FR.143), it is not apparent that the licensee is properly accounting for this uncertainty when conducting the required LPCI flow surveillance testing each refbeling outage.
- 2. Section El.l.2.2(J) on pages 5 7 of the report describes the team's Soding that the RHR system was not designed with adequate minimum Sow protection for continuous Rigt pump operation. According to the report, the RHR pumps might be required to operate in minimum flow mode for a mrximum of 4 to 5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> following a small break loss of coolant accident, but the pump manufacturer could not recommend sustained pump operation at minimum flow for toeger than 30i ninutes. Ahe licen a reportedly revised procedures to require operators to manually trip the pumps within 30 minutes of operation in minimum Sow mode, presumably with guidance to restart the pumps later when required for core cooling. UCS shares the inspection team's stated concern that this manual intervention to ove ome a design denciency is a change to the RHR/LPCI mode of operation as described in the Final Safety Analysis Report.
- 3. Section El.2.2.2(h) on pages 1415 of the report describes the team's Boding of a potential single failure that could cause loss of all service water to both trains of the emergency diesel gm. He team identiBed a non-safety related pressure regulator which supplied air to the solenoid valves to normally closed Sow control valves in the senice water flow path to both trains of emergency diesel generators. The team concluded, "the failure of a single non-safety related pressure regulator could potentially disable both trains of EDGs." %e licensee reportedly performed a commercial dedication on new air pressure regulators. It appears from the report that the Vcrmont Yankee con 6guration permits the failure of a single pressure regulator to prevent service water flow to both emergency diesel generator trains. If this is indcod the configuration, then even a safety related pressure regulator would represent the potential for a single failure disabling both diesel generators. Section 3.2.19 of the Yankee Individual Plant Examination submitted on December 21,1993, indicates that the emergency diesel gener:turs require cooling by the servios water system and that the flow coctrol valws have an air to-close, fall open design he IPE assumes a nonditional probability of 1.52E 03 for service water flow control valves FCV 104-28A/B failing to open on demand. It is not certain that this value conservatively bounds either the non safety related or commercial dedicated pressure regulator. It is also not certain that the DE accurately reflects the single failure vulner bility. In any case, the licensee
- submitted letter BVY 89 17 dated February 16,1989, to the NRC staffin response to Generic Letter 88 14, " Instrument Air Supply System Problems *Affecting Safety Related Equipment." On pages 4 5 of enclosure 1, the licensee stated that "it was veri 6ed that the design of all safety related, air operated components identined is in accordance with its intended function."
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