ML20084K741
| ML20084K741 | |
| Person / Time | |
|---|---|
| Site: | Dresden, 05000000 |
| Issue date: | 09/19/1974 |
| From: | Felmus N COMMONWEALTH EDISON CO. |
| To: | Robert Carlson, Dreher F NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I), US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20084K638 | List: |
| References | |
| NUDOCS 8305190532 | |
| Download: ML20084K741 (1) | |
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C. J. STATHAKIS J. D. SELBY A. P. BRAY
SUBJECT:
RECIRCULATION LOOP", '
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OF A 5 CPM UNIDENTIFIED LEAK IN THE DRWELL.THE DRESDEN 2 FLANT SH 2
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j INSTALLED SUMP MONITORING (ST'SEEM.. A"SMALL CRACK;THROUCH THE PIPE WALL OlEAT EIT IONE) WAS DISCOVEREn ~IN THE FOUR. INCH BYPASS LINE ON,THE B-RECIRCULATION LOOP.
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Address seply to: Post Ofhee Box 767 Chicago, Ilknois 60630 BBS Ltr.8680-74 Dresden Nuclear Power Station R. R. #1 60450 gdidlEr h Morris, Illinois h
September 19, 1974 g
iteg0 t y-/ #7 Y Mr. James G. Koppler, Regional Director 50 P,37 sh Slf ?.[ [
\\;f3 Directorate of Regulatory Operations-Region III
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U. S. Atomic Energy Cocanission
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799 Roosevelt Road
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Glen Ellyn, Illinois 60137
SUBJECT:
REPORT OF ABNORMAL OCCURRDJCE PER SETION 6.6.B 0F THE TECIMICAL SPIEIPICATIONS.
PRIMARY SYSTB4 LEAKS.
References:
- 1) Regulatory Guide 1.16 Rev.1 Appendix A
- 2) Notification of Region III of AEC Regulatory Operations Telephone: Mr. F. Maura,1515 heurs en septe= der..13._.1974 Telegram Mr. J. Keppler, 1543 hours0.0179 days <br />0.429 hours <br />0.00255 weeks <br />5.871115e-4 months <br /> on September 13, 1974
- 3) Drawing Number: P&ID W 26 Report Number: 50-237/1974 m 26 Report Dates September 19, 1974 Occurrence Date: September 13, 1974 Facility: Dresden Nuclear Power Station, Morris, Illinois IDDTPIPICATION OF OCCURRD'CE On September 13, 1974, a leak was discovered on line 2-0203B-4"-4 in the "B" reciro. system. The next day a leak was diccovered on line 2-0203A-4"-A in the "A" recire. system. This reprocents an abnormal degradation of a boundary designed to contain radioactive materials.
CONDITIONS PRIOR TO OCCURRB;CE
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At 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> on September 13, 1974, Unit 2 was in shutdown.
DESCRIPTION OP OCCURRSEE At 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> on September 13,~ 1974, Unit 2 was in shutdown due to high drywell leakage. Inspections were in progress to determine the cause of the leakage. At this time, a. leak was discovered on 2B recirc. loop at
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v Mr. Jam a G. Ksppler Ssptemb:r 19, 1974
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the connection of 2B recire. pu=p discharge valve bypass line (2-0203B-4"-A) with the recire. loop (2-0201B-28"-A). The line was cracked at the point where the line is welded to an inverted reducer. The crack was a circumfer-ential crack which ran along approximately 75% of the pipe circumference and was completely through the pipe in two areas. This crack was upstream of the bypass valve and was casily isolatible.
The next day a crack was found on the 2A recire. loop. The crack was also in the 4" equalizins line, but downstream of the bypass valve at the 28"x4" reducer to the 28" recire. riser. This crack consisted of an approximately 3/4" long circumferential crack with about a 1-1/2" tail running along the length of the pipe. Only the circumferential part of the crack was completely through the pipe. This crack was not isolatible.
DESIGNATION OF APPARFNT CAUSE OF OCCURRENCE At this time, no apparent cr.use is known. Pieces of the cracked pipe were sent out for analysis. A followup letter will be written when the results of these analyses are returned.
ANALYSIS OF OCCURRENCE There were no safety consequences to the public or plant personnel as a result of this occurrence because the cracks were found before any major damage was done. All water was contained in the drywell sumps and pumped to Raduaste for processing. The shift b,' shift monitoring of the drywell sumps found this problem immediately and allowed for a safe shutdown before excessive leakage reculted. Had the pipe broken under operation, LPCI, HFCI and core spray were available to provide core cooling.
CORRECTIVE ACTION The 2B loop crack was isolated, the section of cracked pipe cut out, and a new section welded in. The 2A loop is at the present, unisolatible. Plans are being formulated for repairing this crack. The followup letter will include the method used for repairing this crack. Subsequent investigations will be conducted on Unit 3 to disclose similar cracking at the earliest opportunity.
FAILURE DATA These are the first idlures of this type.
Sincerely, B. B. Stephenson Superintendent BBS:do
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