ML20010A085
| ML20010A085 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 07/29/1981 |
| From: | Novak T Office of Nuclear Reactor Regulation |
| To: | Rich Smith VERMONT YANKEE NUCLEAR POWER CORP. |
| References | |
| REF-GTECI-A-10, REF-GTECI-RV, TASK-A-10, TASK-OR NUDOCS 8108110036 | |
| Download: ML20010A085 (3) | |
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,,p Docket No. 50-271 July 29,1981
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Mr. Robert L. Smith r
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Licensing Engineer Ig APG 051981m Tg Vermont Yankee Nuclear Power 16 Wo c r Road NmP h Framingham, Massachusetts 01701 s
Dear Mr. Smith:
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SUBJECT:
IMPLEMENTATION OF UNRESOLVED SAFETY ISSUE A-10, BWR N0ZZLE CRACKING 4
By letter dated January 30, 1981 you provided information regarding h
l implementation of guidance from NUREG-0619 at the Vermont Yankee Nuclear l
Power Plant. NUREG-0619, issued by letter ated November 13, 1980, contained
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the NRC staff's resolution of Unresolved Safety Issue A-10.
q Your position was that no feedwater nozzle modifications should be required at Vermont Yankee, based upon a better-than-average operating record, good procedures, and an interference fit sparger design. You stated that no flaw indications had been discovered during dye penetrant (PT) examinations of the nozzle blend radius in 1977 and 1979. Members of the NRC staff discussed this subject with your engineering staff in a telephone conversation j
on April 16, 1981. Subsequent to this call, you delivered additional informa-tion supporting your case to your NRC Project Manager.
We have reviewed the information made available to us and have not determined that there is technical basis for allowing long-tem operation of the installed feedwater sparger/themal sleeve design at Vermont Yankee. Our bases for this determination are as follows:
(1) Although your operation of the plant, by minimizing thermal cycles, I
certainly is commendable, the fact remains that the feedwater nozzle I
bore surfaces have never been inspected. Regardless of the claims I
made in Teledyne Technical Report TR-2323, you should be aware that the worst nozzle crack to date was discovered in the bore of a feed-water nozzle. It can be agreed that, if PT examination of the blend radius reveals no cracks, there is a good chance that the bore is j
also free of cracks, but the correlation is imperfect and certainly is no substitute for examination of the bore itself. Also, exposure values utilized in your argument take into account blend radius inspections only. The calculated plant lifetime exposure would increase substantially when required bore inspections were performed.
(2) Your argument that annual ultrasonic (UT) examinations, supp1mented by periodic blend radius PT examinations, are a positive means of 8108110036 a1YY29(n zzle integrity, is not substantiated by industry experience PDR ADOCK 05000271
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j with UT techniques. Most recently, experts :laimed to have found a flaw in a feedwater nozzle of an operating reactor. Later inspections by PT and magnetic particle (MT) sho ed nothing. When this experience is coupled with the converse that UT shows nothing "re ortable" but subsequent PT discloses cracking, it is easy to see why the NRC staff places little credence in present UT techniques on the feedwater nozzles.
Industry claiu to the contrary, we have seen nothing to indicate t.'at a reliable, repeatable method for locating and characterizing cracks
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is in use (Machined notches in a lab mockup are not cracks, in our opinion). Worse, we have not yet been told the maximum anticipated undetected flaw size by any of the present techniques. Until ue have such information UT cannot be approved as the sole means of feedwater I
nozzle inspection and cannot, in your case, serve as a justification for no bore inspection by PT.
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(3) We still maintain that the interference fit may loosen with time, allowing leakage to commence. Your planned installation of a bypass leakage detection system therefore begs the question of calibration of the system when undetected leakage begins before installation of 1
the system. In this case, a fallacious baseline could be established and a false sense of security imparted. This is especially true in the case of Vemont Yankee, where the nozzles are still clad and l
where, therefore, the nozzle is very sensitive to leakage : low.
(4) The information about the new spargers acting as crud traps at an operating reactor is an oversimplification of the *= cts and extrapolates to all insta11atic.s what is, indeed, an unlikely occurrence. We have spoken to the operators of the affected reactor and have determined that what was trapped was material resulting from a leaking condensate polisher system. General Electric has been informed of the problem and should i
be taking action. At any rate, NUREG-0619 specifically allows the f
i installation of any other sparger design that meets the NRC criteria, and in fact the NRC has approved alternative designs at two facilities.
l This option is also open to you.
Based on our review, we will require that you follow the guidance and
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schedules of NUREG-0619, and request that you provide a commitment to do so.
l With regard to the control rod drive (CRD) hydraulic system modifications, l
i we are aware of your having rerouted the return line to the reactor water
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cleanup system. However, you provided no information regarding implementation l
of the remainder of the system changes as explained in NUREG-0619. You should submit your commitment to do so.
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Please submit your commitments explained ab se f t9n 45 days of receipt l
of this letter.
If an extension of time b m eend to this letter is l
required, please submit the requested ex pto esnd the bases therefore.
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Mr. Robert L. Smith 3-Although similti requests for commitment have been and will be sent to other licensees regarding their implementation of NUREG-0619 guidance, each request is plant-specific and the effort required in response varies with tha number of deviations from the NRC's guidance. Therefore, the reporting requireinents containe.d in this letter are considered to affect fewer than 10 persons. Accordingly, the requirements are not subject to Office of Management and Budget clearance as required by P.L.96-511, Sincerely.
Thomas Novak, Assistant Director for Operating Reactors Division of Licensing cc: See next page Distribution:
Docket File NRC PDR Local PDR ORB #2 Reading D. Eisenhut T. Ippolito S. Norris V. Rooney 0 ELD I&E (3)
R. kiecker, R. Johnson F. Clemenson, N. Randall K. Kniel, N. Anderson R P. SNn\\ DER.
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