Information Notice No. 88-82: Torus Shells with Corrosion and Degraded Coatings in BWR Containments
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
October 14, 1988
Information Notice No. 88-82: TORUS SHELLS WITH CORROSION AND
DEGRADED COATINGS IN BWR CONTAINMENTS
Addressees:
All holders of operating licenses or construction permits for boiling water
reactors (BWRs).
Purpose:
This information notice is being provided to alert addressees to the discovery
of suppression pool steel shells with corrosion and degraded coatings in BWR
containments. It is expected that recipients will review the information
for applicability to their facilities and consider actions, as appropriate, to
avoid similar problems. However, suggestions contained in this information
notice do not constitute NRC requirements; therefore, no specific action or
written response is required.
Description of Circumstances:
During recent NRC inservice inspections (50-220/88-09 and 50-410/88-09) at the
Nine Mile Point Nuclear Station (NMPNS), inspectors found that the inside
surface of the torus shell at Unit 1, which was designed and constructed as
uncoated, had corroded. Furthermore, the NRC inspectors' independent
thickness measurements of the torus shell revealed several areas in which the
thickness was at or below the minimum specified wall thickness. Based on
additional analysis, it was determined that the shell thickness is acceptable
until June 1989 at which time the licensee will perform an ultrasonic
reexamination of the torus shell. Based on the findings, the licensee is
committed to take corrective actions.
A recent survey of BWRs located in NRC Region I also revealed that some Mark I
tori had experienced degradation of the coating and that cleaning and
recoating were required. The cause of these degradations is not yet fully
understood.
Discussion:
Although the torus shell thinning due to corrosion observed at NMPNS Unit 1
and the coating degradation in tori of other Region I plants have no immediate
effect on plant operation, the NRC staff considers these deficiencies to be
significant because the measured corrosion rates of torus shells are greater
than the corrosion rates assumed as part of the original design. The torus
shell degradation, if it continues, may jeopardize containment integrity.
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October 14, 1988
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Many licensees of BWR plants are currently required to perform periodic visual
inspections of the suppression pool steel shells or liners in accordance with
their technical specifications, but the methods used by licensees vary. Some
licensees examine only those portions of the torus above the water line, and
others employ divers or use cameras to inspect submerged surfaces. Such
inspections can only detect general degradation. Localized degradation such
as pitting can be detected most effectively by draining the torus and
inspecting it under dry conditions. In view of the importance of the
containment to the health and safety of the general public, licensees may wish
to review and evaluate the adequacy of their containment surveillance programs
to determine if any problems similar to those described above exist at their
plants.
This information notice also applies to suppression pools for other types of
BWR containments (Mark II and Mark III), whether built of steel or of concrete
with a steel liner, because the steel shell or liner may degrade through
disintegration of the paint system and /or corrosion of the base metal.
No specific action or written response is required by this information notice.
If you have any questions about this matter, please contact the technical
contact listed below or the Regional Administrator of the appropriate regional
office.
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contact: Chen P. Tan, NRR
(301) 492-0829
Attachment: List of Recently Issued NRC Information Notices
. Attachment
IN 88-82
October 14, 1988
Page 1 of 1
LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
_____________________________________________________________________________
Information Date of
Notice No._____Subject_______________________Issuance_______Issued to________
88-81 Failure of Amp Window 10/7/88 All holders of OLs
Indent Kynar Splices or CPs for nuclear
and Thomas and Betts power, test, and
Nylon Wire Caps During research reactors.
Environmental Quali-
fication Testing
88-80 Unexpected Piping Movement 10/7/88 All holders of OLs
Attributed to Thermal or CPs for PWRs.
Stratification
88-79 Misuse of Flashing Lights l0/7/88 All holders of OLs
for High Radiation Area or CPs for nuclear
Controls power reactors.
88-69, Supp 1 Movable Contact Finger 9/29/88 All holders of OLs
Binding in HFA Relays or CPs for nuclear
Manufactured by General power reactors.
Electric (GE)
88-78 Implementation of Revised 9/22/88 All holders of OLs
NRC-Administered Requali- or CPs for nuclear
fication Examinations power reactors.
88-77 Inadvertent Reactor 9/22/88 All holders of OLs
Vessel Overfill or CPs for BWRs.
88-76 Recent Discovery of a 9/19/88 All holders of OLs
Phenomenon not Previously or CPs for nuclear
Considered in the Design power reactors.
of Secondary Containment
Pressure Control
88-75 Disabling of Diesel 9/16/88 All holders of OLs
Generator Output Circuit or CPs for nuclear
Breakers by Anti-Pump power reactors.
Circuitry
88-74 Potentially Inadequate 9/14/88 All holders of OLs
Performance of ECCS in or CPs for W and
PWRs During Recirculation B&W-designed
Operation Following a LOCA nuclear power
reactors.
_____________________________________________________________________________
OL = Operating License
CP = Construction Permit
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