ML20024G646
| ML20024G646 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 06/29/1972 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Wachter L NORTHERN STATES POWER CO. |
| References | |
| NUDOCS 9102140368 | |
| Download: ML20024G646 (3) | |
Text
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UNITED STATES b
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ATOMIC ENERGY COMMISSION DIRECTOR ATE OF REGULATORY OPER ATIONS
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- 'd t n e 799 ROOSCVELT ROAD ygu puoug GLEN CLLYN, ILLINOIS 6o137 (312) 856-2660 June 29, 1972 Northern States Power Company Docket No. 50-263 ATTN:
Mr. Leo Wachter, Vice President Power Production 419 Nicollet Avenue Minneapolis, Minnesota 53401 G entlemen:
Information obtained during inspections conducted by the Directorate of Regulatory Operations, has disclosed that a number of facilities have been equipped with valves with wall thicknesses below the minimum requirements specified by the applicable codes, standards and procurement specifications.
In other instances, licensees have not been able to document whether or not their valves met minimum wall thickness require-ments. Our survey of this subject has disclosed that the matter is not O
11mited te anv c1 ass ef 11censee er v 1ve s=>>11er.
In light of the above information, you are requested to verify, through manufacturing records or other suitable means, that valves important to nuclear safety installed or to be installed at your facility meet the minimum wall thickness requirements of the specified codes or standards. To the extent that verification records are currently available, you are requested to promptly accumulate those records at the plant site, and to advise this of fic.e within thirty (30) days of the date of this letter, of what records are availabic and when our inspector may examine them at the plant site.
In the event that records are not currently available, you are requested to advise this of fice within thirty (30) days, of your plans and schedules for demonstrating by saltable alternate means, that valves important to nuclear safety installed or to be installed at your facility are acceptable with respect to wall thickness. Records of conformance shall be maintained current with inspections performed.
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Northern States Power Company June 29,1972 The valves which require demonstration of acceptable wall thickness are the following:
Each valve within the reactor coolant pressure boundary, as defined in subsection 50.55(a) (Codes and Standards) of 10 CFR 50, where the valve is:
(a) over 1-inch nominal pipe size for pressurized water reactors; (b) over ik-inch nominal pipe size in water lines for boiling water reactors; (c),over 2 -inch nominal pipe size in steam lines for boiling
. water reactors.
The following techniques are considered to be a sufficient demonstration of acceptable wall thickness. Alternate techniques may be offered, but there is no assurance that they will be found acceptable:
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(1) Documented direct physical measurement of actual wall thickness, with comparison to specified minimum wall thickness.
(2) Documented results of ultrasonic measurement of wall thickness, with comparison to specified minimum wall thickness, and documentation that the ultrasonic measure-ment technique is demonstrated to have a maximum error in repeatability and accuracy, of not more than 2% of the wall thickness.
(3) Wall thicknesses, verified by either of the above techniques, to be not less than 90% of specified minimum wall thickness will be acceptable, provided that the documented mechanical characteristics of the material exceed the specification minimum by an amount sufficient to compensate for the measured reduction in wall thickness, (4) "Specified Minimum Wall Thickness" as used t.bove, means the wall thickness required by the relevant codes and standards (e.g., ASA B31.1 (1955); USAS B31.1.0 (1967);
USAS B16.5; MSS-SP-66) in effect on the date of the purchase order.
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Northern States Power Company June 29, 1972 (5) Certain of your valves may have, for procurement convenience, been ordered to ratings higher than actually required by service conditions.
In such inntances, you may, if you wish, provide for our review, nn engineering justification for accepting valves which do not conform to procurement specifications, but do in your opinion, satisfy service requirements. Such justification should be premptly tranreitted to thic offico, in ten (10) copies.
(6) In certain instances, you may wish to repair vsives found to have vall thickness below the specified minimum. In such instcnces you are requested to provide this office for our review, the proposed repair procedure, including a description of techniques to be used to verify the acceptebility of the repaired conronente.
Such a proposed procedure should also be submitted in ton (10) cepics.
O Acceptable docunentation of conformance with the abovo requireisents must be completed within three (3) years of the date of thin lettor.
Very truly youre, Ecyce B. Grinr Rep,icsnal Director l
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