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 STATES NUCLEAR REGULATORY

COMMISSION

OFFICE OF INSPECTION

AND ENFORCEMENT

WASHINGTON, D.C. 20555 March 26, 1979 IE Information

Notice No. 79-07 RUPTURE OF RADWASTE TANKS Description

of Circumstances:

In November, 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 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

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, formed 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, applied 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

o*(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) can minimize the probability

of such an event. Prevention

of such events 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.

No specific action or written response to this Information

Notice is required.

If you require additional

information

regarding

this subject, contact the Director of the appropriate

NRC Regional Office.

IE Information

Notice No. 79-07 March 26, 1979 LISTING OF IE INFORMATION

NOTICES ISSUED IN 1979 Information

Notice No.Subject Date Issued 79-01 79-02 79-03 79-04 79-05 79-06 Bergen-Paterson

Hydraulic Shock and Sway Arrestor Attempted

Extortion

-Low Enriched Uranium Limitorque

Valve Geared Limit Switch Lubricant Degradation

of Engineered

Safety Features Use of Improper Materials in Safety-Related

Components

Stress Analysis of Safety-Related

Piping Rupture of Radwaste Tanks 2/2/79 2/2/79 2/9/79 Issued To All power reactor facilities

with an OL or a CP All Fuel Facilities

All power reactor facilities

with an OL or a CP 2/16/79 All power reactor facilities

with an OL or a CP 3/21/79 All power reactor facilities

with an OL or CP 3/23/79 All Holders of Reactor OL or CP 3/26/79 All power reactor facilities

with an OL or CP 79-07