ML20127H533
| ML20127H533 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 01/30/1975 |
| From: | Mayer L NORTHERN STATES POWER CO. |
| To: | Anthony Giambusso US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| AO-75-03, AO-75-3, NUDOCS 9211180538 | |
| Download: ML20127H533 (5) | |
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NSF R'o J6l 'X D6Cii' I?
NORTHERH STATES POWER COMPANY M lN N E A PO U S. MIN N E S OTA 3 9400 h
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Mr A Giambusso, Director g.
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Washington, DC 20555 B
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Dear Mr Giambusso:
y MONTICELLO NUCLEAR GENERATING PIANT Docket No. 50-263 License No. DPR-22 Licensee Event Report to the NRC Crack Indications in Recirculation Bypass Piping Attached are the Licensee Event Report and a supplementary report for this Occurrence.
Yours very truly, ha L 0 Mayer, PE Manager of Nuclear Support Services IDM/DtH/ak cc: J G Keppler N!,l;;._ s.; -
G Charnoff Minnesota Pollution Control Agency Attn:
E A Pryzina 1145 9211180538 750130 PDR ADOCK 0500026S S
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SUPPLEMENT TO LICENSEE EVENT REPORT TO THE NRC Crack Indications in Recir_culation Bypass Piping Supplemental Information:
1.
Report Number: A0 263/75-03 2a.
Report Dat;: 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 4
Reactor Recirculation System 4-inch diameter bypass lines during the inservice inspection.
I 5.
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 weld in loop B of the reactor recirculation system 4-inch diameter bypass lines. Radiographic examination of these three velds 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 amplitude of the ultrasonic signal for this weld was relatively low, the signal pattern was similar to the three welds that were rejected; therefore, this weld was also rejected (see attached Figure).
7.
Designation of Apparent Cause of Occurrence:
The cause is unknown. It appefrs to be a generic problem similar to problems experienced at other BRR 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.
Regde:;
A fil6 JCENSEE EVENT REPORT CONTROL BLOCK:l l
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l (g MHRfT ALL Resumen ageMMIMATIOnl) h a et5nul-30'Z5 ANE LcENSE NUMBER PE TV h l Ml Nl MlN lP l1 l l 0 l 0l-l0 l0 l0 l 0 l 0 l-l 0l 0l l 4l1 l 1l 1l1 l l0l1l 7 89 14 15 25 26 30 31 32
"'7pU ENE cATE00RY T
OoCEET NUMBER EVENT DATE
' REPORT DATE O
CON'T l P l 0l
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l 0l 5l 0l-l Ol2 l6 l3 l l 0 l 1l 2l0 17 l5 l l 0 l 1 l 3 l 0 l7 l5 l 7 8 57 58 59 60 61 68 09 74 75 80 EVENT DESCRIPTION DE l During inservice inspection linear indications were detected by ultrasonic l
7 89 80
$ l exantination (two velds Loop A. one veld Loop B) of reactor recirculation 4-inch l
7 89 80 lhvnnen 7 89
linen.
R nr11 oernnh a of the 1 welds verified one indication (in heat affected l
80 3G l zone). No previous occurrence.
Pipe to be replaced prior to startup.
(A0 75-03) l 7 89 80
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7 89 PwE 80 CO$E COMPONENT CODE s
A M
A v0utoN BE U J 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 DE l Cause unknown. Laboratory analysis of removed piping to be performed.
Piping to l
7 89 80 gg l be reinspected during fall 1975 refueling outage.
l 7 89 80 STA
% POWER OTHER STATUS DISCOVERY DISCOVERY OESCRIPTON l.n]
1010101 I n I lol I
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10 12 13 44 45 46 80 LE EO O EASE AMOUNT Of ACTiv!TY LOCATON OF RELEASE DE lzJ Lz J l n l
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10 11 44 45 80 PERSONNEL EXPOSURES NUMBER TYPE DESCRIPTON nm 1010101 Lz_J l NA I
7 89 11 12 13 80 PERSONNEL INJUAIES NUMBER DESCRiPTON 101010l I NA I
14 7 89 11 12 80 OFFSITE CONSEQUENCES DE l NA l
7 89 80 LOSS OR DAMAGE TO FACILITY TYPE DESCRIPTON D2 LzJ l n i
7 89 10 80 PU8LICITY DG l Press Release - Monticello pipe cracks, 1-22-75 l
'/ 89 80 ADDITIONAL FACTORS 98 l After comparison of ultrasonic records from November inspection, a fourth weld was l
7 80 80 gl conservatively rejected and removed.
l 7 89 80 NAME:
Phil Krumpos 612-330-6737 PHONE:
GPO 889.g97
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2-8.
Analysis of Occurrenc.e:
i 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 steel) will be sent to a laboratory for metallurgical.
examination.
4 10.
Failure Date:
Not applicable.
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