Information Notice 1979-07, Rupture of Radwaste Tanks

Rupture of Radwaste Tanks

ML031180125
Person / Time
Site:	Waterford, 05000000
Issue date:	03/26/1979
From:	NRC/IE
To:
References
IN-79-007, NUDOCS 7904120337
Download: ML031180125 (3)

UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF INSPECTION AND ENFORCEMENTWASHINGTON, D.C. 20555March 26, 1979IE Information Notice No. 79-07RUPTURE OF RADWASTE TANKS

Description of Circumstances

In November, 1977 a radwaste tank ruptured at the Millstone NuclearPower Station. Two problems led to the tank failure. First, the tankvent, which was intended to relieve excessive pressure in the radwastetank, had been plugged by accumulated solidified concentrates. Second,corrosion had weakened the capability of the radwaste tank to withstandpressure. Individually, or in combination, these problems were causa-tive factors in the rupture of the radwaste tank due to overpressurization.The Licensee Event Report states that an aerated waste concentrates tankwas overpressurized and ruptured. The tank contained radwaste evapo-rator concentrates with a 10-12 percent boric acid concentration. Theseconcentrates, when cooled to ambient temperatures, formed a solidcrystaline structure. Apparently, concentrate had entered the vent lineby previous tank overflows or purging of air through the tank so that asolid buildup occurred in the vent line. This buildup eventually led toa flow blockage in the vent line. The licensee, in an attempt to blowout or clear a radwaste pipe, applied 100 PSI air pressure to the tank.The tank was designed for 15 PSI and the plugged vent could not relievepressure. Therefore, the tank overpressurized and ruptured.This tank had a history of corrosion problems such that the corrosionprobably caused some weakness which contributed to the rupture. Thetank was constructed of type 304 stainless steel. The plant was a sea-coast site such that significant amounts of chlorides were present inthe aerated waste system and, consequently, in the waste concentratetank. The presence of significant amounts of chlorides, coupled withresidual welding stresses in the type 304 stainless steel, resulted inchloride stress corrosion.Since radwaste tanks of this type are used at most power reactors, thepotential may exist for similar events at other power reactors. Also,such events can be avoided by proper procedures and periodic examinationo*(3 IE Information Notice No. 79-07 March 26, 1979 if personnel are aware of the problem. In addition, proper considera-tion of design features (e.g., materials selection and vent designs) canminimize the probability of such an event. Prevention of such eventswill minimize, the possibility of personal injury, in-plant contamination,releases of radioactivity, and occupational radiation exposure resultingfrom the repair and clean-up operations.No specific action or written response to this Information Notice isrequired. If you require additional information regarding this subject,contact the Director of the appropriate NRC Regional Offic IE Information Notice No. 79-07March 26, 1979LISTING OF IE INFORMATION NOTICESISSUED IN 1979InformationNotice No.SubjectDateIssued79-0179-0279-0379-0479-0579-06Bergen-Paterson HydraulicShock and Sway ArrestorAttempted Extortion -Low Enriched UraniumLimitorque Valve GearedLimit Switch LubricantDegradation ofEngineeredSafety FeaturesUse of Improper Materialsin Safety-Related ComponentsStress Analysis ofSafety-Related PipingRupture of Radwaste Tanks2/2/792/2/792/9/79Issued ToAll power reactorfacilities with anOL or a CPAll Fuel FacilitiesAll power reactorfacilities with anOL or a CP2/16/79 All power reactorfacilities with anOL or a CP3/21/79 All power reactorfacilities with anOL or CP3/23/79 All Holders ofReactor OL or CP3/26/79 All power reactorfacilities with anOL or CP79-07