Information Notice 1979-07, 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
All Fuel Facilities
All power reactor
facilities with an
2/16/79
All power reactor
facilities with an
3/21/79
All power reactor
facilities with an
3/23/79
All Holders of
3/26/79
All power reactor
facilities with an
79-07