ML20084R768
| ML20084R768 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 12/06/1974 |
| From: | Stephenson B COMMONWEALTH EDISON CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| Shared Package | |
| ML20084R769 | List: |
| References | |
| 869-74, AO-50-249-74-37, NUDOCS 8306150548 | |
| Download: ML20084R768 (3) | |
Text
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Commonwontth Edison i
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ChicagR'.non 60690 DBS Ltr.f869-74 Dresden Nuclear Power Station R. R. #1 7.
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Morris, Illinois 60450-Decceber 6, 1974 O~'y J ni f
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A Mr. James G. Ecppler, Regier.a1 Director 4
Directorate of Regulatory Operations-Region III d,\\4,l*< # b 4-p ;Y s
U. S. Atomic Encrcy Co:=ission f7
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799 Roccovelt Road Glen Ellyn, Illinois 60137 NC "
SUDJET: REPORT OF_ AE*O??.AL OCCURRE CE PER SECTIO'T 6.6.A OF THE TECEIICAL SPECIPICATICIS ret.CTOR FT'i'D 1"u2P 33 IGmEl FLO'.1 LII S LEAKAGE
References:
- 1) Regulatory Guide 1.16 Rev.1 Appendix A
- 2) Notification of Region III of AEC Regulatory Operations Telephone: Mr. C. Pcierabend, 1400 hours0.0162 days <br />0.389 hours <br />0.00231 weeks <br />5.327e-4 months <br /> on Decc=ber 2, 1974 Tologram: Mr. J. Keppler, 0835 hours0.00966 days <br />0.232 hours <br />0.00138 weeks <br />3.177175e-4 months <br /> on December 3, 1974
- 3) Drawing Number: M-347 (S&L)
- 4) Deviation Reports 50-237/74-41 ( &-30-74), 50-237/74-46 (9-20-74),
50-249/74-33 (11-19-74), and 50-249/74-36 (12-10-74).
Report Nu=ber 9/74-3h Report Date: December 6, 1974 Occurrence Dator December 1, 1974 Facility: Dresden Nuclear Power Station, Morris, Illinois IDE2."PIPICATIO:I OP OCCITitRE:CE On December 1,1974 a emall leak uns discovered on reactor feed ramp 3B minimum flow line 3-3205D. This condition is an cbnormal degradation of a boundary d:, signed to contain radioactivo materials as defined in Regulatory f
Position C.2.a(1)(c).
CONDITIO!!S PRIOR TO CCCURRE:CE
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When the lcnk was discovered, the Unit 3 reactor was shutdown.
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COPY SElfT REGION -
Mr. James G. X ler Decen.ber 6,1974
. j'::I.RIWION OF OCCURRE:CE The pinhole Icak on the minitum flow line was found during a routine plant inspection at 0230 hours0.00266 days <br />0.0639 hours <br />3.80291e-4 weeks <br />8.7515e-5 months <br /> on December 1, 1974.
Since the unit was aircady chutdown, the i:cnediate action taken was to write a work request to repair the leak.
DESIGNATION OF APP /.RE T CAUSE OP OCCURRE:CE (Unucual Service Condition)
The pinhole leak on the pipe was caused by crosion of the pipe from within.
The high velocity turbulent flow in the pipe led to cavitation of the fluid which cauced the crocion.
ANALYSIS OF OCCURRE:CE Due to the cize of the hole in the pipe, only minor leakage of reactor fced-water was involved. If the unit had been running at normal power operation, no Icakage would have occurred because the reactor feed pump mininum flow lines are belou atmosphoric proccure during operation and contain water only during startups, chutdowns, and low pouer operations.
The effect of the leak was to take it more difficult to maintain condencer vacuum, but no cafety implicaticns were caused by this.
Since this type of Icak grous slowly due to the mechanicms involved and the plant is frequently incpected, the poacibility of a pipo rupture or failure, which would cause loca of vacuum and reactor feedwater 1cakage during shut--
down or startup, is highly unlikely.
The health and cafety of pland perconnel or the general public was not jeopardized by this occurrence.
CORRECTIVE ACTION The leaking pipe uas icolated and the leak was repaired using certified uclding materials and techniques. The thickness in the area of the leak was built up with ucld bead, and then a plate was uelded over the leak.
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To prevent this type of incident from occurring again, there are two modi-fications in progress, one for each of Units 2 and 3 - M12-2-74-161 and 1112-3-74-164, to replace the one foot section of piping on the reactor feed pump ninimum flow lines where the cavitation has been occurring, uith a pipe constructed of a chrontium-colybdenum steel alloy. This alloy is more durable than the carbcn steel now being used.
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l'h rm F.r. James G. E iler (u)
December 6, 1974 v,
,FMLURE inTA
. 5 These led.c on the reactor feed pump min'ir:um flow lines have been a recurring prob".cu on both Unita 2 and 3. (See Reference 5). The leaks occur in a 6"-
diameter coaalers schedule 120 class 900 heavy carbon steel of ASIn claccifi-cation A106 Gr.B.
Sincerely,
(;m, ~ ~f t itrC%.)
. :re If D. Stephon::on Superintendent BBS:ELS:do e