Information Notice No. 79-07, Rupture of Radwaste
March 23, 1979
MEMORANDUM FOR: B. H. Grier, Director, Region I
J. P. O'Reilly, Director, Region II
J. G. Keppler, Director, Region III
K. V. Seyfrit, Director, Region IV
R. H. Engelken, Director, Region V
FROM: J. H. Sniezek, Director, Division of Fuel Facilities
and Materials Safety Inspection, IE
SUBJECT: Information Notice No. 79-07, RUPTURE OF RADWASTE
The subject Information Notice No. is transmitted for issuance on March 26,
1979. The Information Notice should be issued to all power reactor
facilities with an operating license or a construction permit.
Enclosed is a draft copy of the transmittal letter. No inspection followup
is necessary since no action by the licensee is requested.
J. H. Sniezek, Director
Division of Fuel Facilities and
Materials Safety Inspection
Office of Inspection and Enforcement
1. IE Information Notice
2. Draft Transmittal Letter
CONTACT: L. J. Cunningham, IE
(Draft transmittal letter for Information Notice No. 79-07 to all power
reactor facilities with an operating license or a construction permit.)
Information Notice No. 79-07
The enclosed 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.
Information Notice No.
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
March 26, 1979
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 causative 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 evaporator
concentrates with a 10-12 percent boric acid concentration. These
concentrates, when cooled to ambient temperatures, formed a solid
crystalline 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 seacoast 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.
Information Notice No. 79-07 March 26, 1979
Page 2 of 2
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 if
personnel are aware of the problem. In addition, proper consideration 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.
List of IE Information
Notices Issued in 1979
Page Last Reviewed/Updated Friday, May 22, 2015