ML19274E869
| ML19274E869 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 03/26/1979 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Johari Moore SOUTHERN CALIFORNIA EDISON CO. |
| References | |
| NUDOCS 7904280203 | |
| Download: ML19274E869 (1) | |
Text
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'4, UNITED STATES ev NUCLEAR REGULATORY COMMISslON f,$<-
HECION V
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SulTE 202. WAl. NUT CilE T K PL AZ A O,
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- d ALNUT CREEK, C ALIF ORNI A 9453G March 26,1979 Docket Nos. 50-206 50-361 50-362 Southern California Edison Company P. O. Box 800 2244 Walnut Grove Avenue Rosemead, California 91770 Attention: Mr. Jack B. Moore Vice President Gentlemen:
The enclosed IE Information Notice No. 79-07 is forwarded to you for information.
No specific action is requested and no written response is required.
If you desire additional information regarding this matter, please contact this office.
Sincerely, (bW)~,cGNA R. H. Engelken Director
Enclosures:
1.
IE Information Notice No. 79-07 2.
List of IE Information Notices Issued in 1979 cc w/ encl:
J. M. Curran, SCE J. T. Head, SCE J. H. Drake, SCE 7 9 04 28 0 2es
UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF IllSPECTION AflD EflFORCEMENT WASHIflGTON, D.C.
20555 March 26, 1979 IE Information Notice flo. 79-07 RUPTURE OF RADWASTE TANKS Description of Circumstances:
In flovember,1977 a radwaste tank ruptured at the Millstone Nuclear Power Station.
Two problems led to the tank failure.
First, the tank vent, which was intended to relieve excessive pressure in the radwaste tank, had been plugged by accumulated solidified concentrates.
- Second, corrosion had weakened the capability of the radwaste tank to withstand pressure.
Individually, or in combination, these problens were causa-tive factors in the rupture of the radwaste tank due to overpressurization.
The Licensee Event Report states that an aerated waste concentrates tank was overpressurized and ruptured. The tank contained radwaste evapo-rator concentrates with a 10-12 percent boric acid concentration. These concentrates, when cooled to ambient temperatures, fermed a solid crystaline structure. Apparently, concentrate had entered the vent line by previous tank overflows or purging of air through the tank so that a solid buildup occurred in the vent line.
This buildup eventually led to a flow blockage in the vent line. The licensee, in an attempt to blow out or clear a radwaste pipe, applud 100 PSI air pressure to the tank.
The tank was designed for 15 PSI and the plugged vent could not relieve pressure. Therefore, the tank overpressurized and ruptured.
This tank had a history of corrosion problems such that the corrosion probably caused some weakness which contributed to the rupture.
The tank was constructed of type 304 stainless steel. The plant was a sea-coast site such that significant amounts of chlorides were present in the aerated waste system and, consequently, in the waste concentrate tank. The presence of significant amounts of chlorides, coupled with residual welding stresses in the type 304 stainless steel, resulted in chloride stress corrosion.
Since radwaste tanks of this type are used at most power reactors, the potential may exist for similar events at other power reactors.
- Also, such events can be avoided by proper procedures and periodic examination gqel t z c,357
- 7) ufe
March 26, 1979 IE Infomation flotice fio. 79-07 Page 2 of 2 I
In addition, proper considera-if personnel are aware of the problem.
tion of design features (e.g., materials selection and vent designs) can Prevention of such events minimize the probability of such an event.
will minimize the possibility of personal injury, in-plant contamination, releases of radioactivity, and occupational radiation exposure resulting from the repair and clean-up operations.
I tio specific action or written response to this Information fr required.
contact the Director of the appropriate fiRC Regional Office.
IE Information Notice No. 79-07 March 26,1979 LISTING 0F IE INFORMATION NOTICES ISSUED IN 1979 Information Subject Date Issued To Notice No.
Issued 79-01 Bergen-Paterson Hydraulic 2/2/79 All power reactor Shock and Sway Arrestor facilities with an OL or a CP 79-02 Attempted Extortion -
2/2/79 All Fuel Facilities low Enriched Uranium 79-03 Limitorque Valve Geared 2/9/79 All power reactor Limit Switch Lubricent facilities with an OL or a CP 79-04 Degradation of 2/16/79 All power reactor Engineered facilities with an Safety Features OL or a CP 79-05 Use of Improper Materials 3/21/79 All power reactor in Safety-Related Components facilities with an OL or CP 79-06 Stress Analysis of 3/23/79 All Holders of Safety-Related Piping Reactor OL or CP 79-07 Rupture of Radwaste Tanks 3/26/79 All power reactor facilities with an OL or CP Enclosure Page 1 of 1