ML20127L223

Forwards NRC Bulletin 74-10B Re Failures in 4-inch Bypass Piping at Dresden-2

ML20127L223
Person / Time
Site:	Monticello, Dresden
Issue date:	07/31/1977
From:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:	Wachter L NORTHERN STATES POWER CO.
References
IEB-74-10, NUDOCS 9211230460
Download: ML20127L223 (3)

Text

North:rn Stat 03 Power Corp:ny d

Docket No. 50-263 A'f7N Mr. Ico Pachter, Vice President Towr Production and System Operation [)

414 Nicollet Hall Winneapolis, Minnesota 55401 centlement i

Enclosed is IE Du11stin No.74-10B, which amende the description of the circumstances discussed in RD Bulletin No.74-10A and requests additional l

actions by you.

Should you have questions rosarding this Bulletin or the actions requested of you, please contact this office.

$ Sincerely, James C. Kappler Regional Director

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Enclosures 1E Bulletin No.74-10B 1

Approved by ( 7, 3-180155 (R0072), clearance expires 7/31/77.

Approval was . .ven under a blanket clearance rpecifically for identified ge.oeric problems.

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I January 27, 1975

, IE Bulletin No.74-10B 1

FAILURES IN 4-INCH BYPASS PIPING AT DRESDEN-2 I '

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REFERENCE:

R0 BULLETINS NO. 74-10. DATED SEPTUiBER 19, 1974 l AND NO.74-10A, DATED DECDiBER 17, 1974)

DESCRIPTION OF CIRCUMSTANCES (AMENDED):

Cracks similar to those described in RO Bulletins 74-10 and 74-10A have l been revealed during reexamination of the 4-inch bypass piping at five boiling water reactor f acilities (including Dresden-2) since mid-December 1974. All the facilities are of jet-pump design. In each instance where cracks have been revealed, the same welds had been examined pre-l viously (during September-November 1974) and no cracks were revealed at 4

that time.

j A special study group, comprised of key technical members of the Nuclear j Regulatory Commission staff, is currently studying the causes of the cracks which have been experienced. Consultants from other government agencies are also participating in the study.

In the interim, pending recommendations of the Commission's special study i group, additional actions are necessary by licensees to insure continued l close surveillance of reactor coolant leakage.

ACTIONS REQUESTED OF LICENSEES (AMENDED):

{ For all boiling water reactor facilities of jet-pump design with operating license:

1. Upon completion of those actions described in R0 Bulletin 74-10A, impicment the following reactor coolant leakage detection program:

If (within the sensitivity specified in paragraph C.S. of Regulatory Guide 1.45) any reactor coolant leakage detection system indicates, i within a period of 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> or less, either an increase in unidentified leakage to twice the determined normal rate of unidentified Icakage or an increase in the rate of unidentified leakage by two (2.0)-gpm or more:

a. Initiate plant shutdown immediately, and

b. Determine the source of increased Icakage prior to resuming operation.

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'E Bulletin No.74-10B January 27, 1975 I .

c. If there is evidence of leakage from the 4-inch bypass piping, reexamine (by ultrasonic or other suitable volumetric inspection technique), all accessible velds in the bypass piping lines.

i (In no case, however, shall the rate of leakage exceed that specified in the technical specifications without those actions required by the technical specifications being taken.)

2. Notify this office, in writing within 10 days of your receipt of this Bulletin, of your intent to implement the actions described in 1.,

above.

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