ML20058K723
| ML20058K723 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 01/30/1975 |
| From: | Krumpos P, Mayer L NORTHERN STATES POWER CO. |
| To: | Anthony Giambusso NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| NUDOCS 9102130537 | |
| Download: ML20058K723 (5) | |
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MIN N E A PO U S, MIN N E SCTA 55401 January 30, 1975 pM, a
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Division of Reactor Licensing U S Nuclear Regulatory Commission
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Washington, DC 20555
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Dear Mr Giambun.;s:
MONTICELLO NUCLEAR GENERATING PIANT Docket No. 50-263 License No. DPR-22 Licensee Event Report to the NRC Crack Indications in Recirculation Evpass Piping Attached are the Licensee Event Report and a supplementary report for this occurrence.
Yours very truly,
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L 0 Mayer, PE Ms.iager of Nuclear Support Services IDM/DMM/ak cc: J G Keppler G Charnoff Minnesota Pollution Control Agency Attn:
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9102130537 750130
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\\ l SUPPLEMENT TO LICENSEE EVENT REFORT TO THE NRC f
Crack Indications in Recirculation Bypass Piping
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Supplemental Information:
i 1.
Report Number: A0 263/75-03 2a.
Report Date: January 30, 1975 3.
Facility: Monticello Nuclear Generating Plant Monticello, Minnesota 55362 4.
Identification of Occurrence:
This report concerns the detection of crack-like indications in the Reactor Recirculation System 4-inch diameter bypass lines during the inservice inspection.
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Conditions Prior to Occurrence:
Refueling Shutdown - A refueling outage was in progress at the time of the occurrence.
6.
Description of occurrence:
On January 20, 1975, during the inservice inspection of the reactor coolant system, linear indications were detected by ultrasonic examination in two welds in loop A and one veld in loop B of the reactor recirculation system 4-inch diameter bypass lines. Radiographic examination of these three welds definitely verified the presence of a linear indication in one of these welds. The radiograph showed the indication to be located in the veld heat-affected zone.
After a thorough review and study of all of the ultrasonic recordings and comparing inspection results obtained in November, 1974, with the present results, a fourth veld became a suspect. This weld was located in loop A.
Although the a=plitude of the ultrasonic signal for this weld was relatively low, the signal pattern was similar to the three velds that were rejected; therefore, this veld was also rejected (see attached Figure).
7.
Designation of Annarent Cause of Occurrence:
The cause is unknown. It appears to be a generic problem similar to problems experienced at other BJR facilities. Identical inspections performed in November, 1974, revealed no unacceptable indications in these same welds. Indications which were detected in the November inspection were of a magnitude and nature such that they were indiscernible from the weld root I.D.
m UCENSEE EVENT REPORi CON 7AOL BLOCK:l l
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[ptaAsa PRWWT ALL REeustED NtPORetATION) 1 6
E tcENSE NUMBER PE TYPE l Ml Nl MlN lP l1 l l 0 l 0 l-10 l0 l0 l 0 l 0 l-l 0l 0l l 4l1 l 1l 1l1 l l0l1l O9 7 89 14 15 25 26 30 31 32 CATEGORY TP S
NOCKET NUMEiER EVENT DATE REPORT DATE
' O 9 CONT l P l O l lTl lLl l 0) 5l 0l-l 0l2 l6 l3 l l 0 l 1l 2l0 l7 l5 l l 0 l 1 l 3 l 0 l7 l5 l 7 8 57 58 59 60 61 68 69 74 75 80 EVENT DESCRIPTION
@ l During inservice inspection linear indications were detected by ultrasonic l
7 89 30
$ l examination (two velds Loop A, one veld Loop B) of reactor recirculation 4-inch l
7 89 80 3E l hvnnna linea.
Mndfoernnha of the 'l velds verified one indiention (in hest affected l
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Pipe to be replaced prior to startup.
(A0 75-03) l 7 89 80 EI I
i 7 89 prwE 80 C DE CODE COMPONENT CODE R
MANUFACTURLR VOLATON
$ lC l B l W lP lI lP lEl Xl Xl l Nl lG l2 l5 l5 l 7 89 10 11 12 17 43 44 47 48 CAUSE DESCRIPTION 30 l Cause unknown. Laboratory analysis of removed pipinst to be cerformed.
Pipinst to l
7 89 80 Q l be reinspected during fall 1975 refueling outage.
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FACUTy
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STATUS
% POWER OTHER STATUS DISCOVERY OlSCOVERY ZE SCRIPTION i
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10 12 13 44 45 46 80 LEA EO - 0 LEASE AMOUNT OF ACTIVITV LOCATION OF RELEAE.E BE LzJ LzJ l NA I
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^4 45 80 PERSONNEL EXPOSURES NUMBER TYPE DESCRIPTION DE l 0 l 0 l 0l
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7 89 11 12 13 80 PERSONNEL INJURIES NUMBER DESCAIPTION H 10lol01 l
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7 89 11 12 60 0 FSITE CONSEQUENCES 3;
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7 89 80 LOSS OR DAMAGE TO FACILITY TYPE DESCRIPTON
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7 89 10 80 PUBLICTTY DE l Press Release - Monticello pipe cracks, 1-22-75 l
7 89 80 ADOITIONAL FACTORS l
D@ l After comparison of ultrasonic records from November inspection, a fourth veld was l
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r hl conservatively rejected and removed.
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7 89 80 NAME:
Phil Krumpos 612-330-6737 PHONE:
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Analysis of Occurrence:
This occurrence had no effect on the public health and safety.
Assuming these linear indications are cracks, and assuming they would have propagated through the pipe wall, the resultant water leaks would have been detected by the drywell sump monitoring system. In the un-likely event of a gross failure of a four-inch bypass loop, the resultant break would be well within the capability of the ECCS System.
9.
Corrective Action:
Segments of both pipe loops which contain the four rejected welds are being removed and replaced. This piping (schedule 80, type 304 stainless stael) will be sent to a laboratory for metallurgical examination.
10.
Failure Date:
Not applicable.
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