Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
SSINS NO.: 6835
IN 85-26
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
April 2, 1985
Information Notice No. 85-26: VACUUM RELIEF SYSTEM FOR BOILING WATER
REACTOR MARK I AND MARK II CONTAINMENTS
Addressees:
All boiling water reactor (BWR) facilities having a Mark I or Mark II
containment and holding either an operating license (OL) or construction
permit (CP).
Purpose:
This notice is provided to alert recipients of potentially significant
safety problems pertaining to the primary containment suppression
chamber-to-reactor building vacuum relief system in BWRs with Mark I and
Mark II containments. It is expected that recipients will review the
information for applicability to their facilities and consider actions, if
appropriate, to preclude similar problems occurring at their facilities.
However, suggestions contained in this information notice do not constitute
NRC requirements; therefore, no specific action or written response is
required.
Description of Circumstances:
Early in 1980, General Electric (GE) was notified by Philadelphia Electric
Company (PECO) of a safety concern regarding the installed condition of the
torus-to-reactor building vacuum relief system at Peach Bottom 2 and 3. The
concern involved the equipment safety classification and separation of the
controls to the butterfly valves of the system.
The butterfly valves of the torus-to-reactor building vacuum relief system
in BWRs with Mark I containments perform the dual safety function of vacuum
relief and containment isolation. Two identical system arrangements are
provided, each of which can perform the vacuum relief function
independently. In each line, the isolation function is provided by the
normally closed air-operated butterfly valve and a check valve. Either or
both of the safety functions have the potential for being jeopardized if the
controls for the butterfly valves are inadequately separated or the valves
and associated components are classified as non-safety related.
Following a technical review, GE concluded that insufficient technical
information exists within their organization to adequately evaluate this
safety concern for the individual BWR plants. Although the design
requirements pertaining to the torus-to-reactor building vacuum relief
system are generally
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IN 85-26
April 2, 1985
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addressed in the GE specifications, the actual system design is within the
scope of the architect-engineer of a facility. Consequently design configur-
ation is not available within GE for their evaluation on a plant-specific
basis.
Discussion:
After PECO notified GE of this safety concern, GE recommended to the BWR
Owners' Group (BWROG) that facilities with Mark I containments upgrade their
designs. The concern was discussed in several BWROG meetings during 1981-82,
and it was concluded that any further action would only be appropriate on a
plant-specific basis rather than on a generic basis.
The NRC staff has discussed the safety concern with GE and BWROG representa-
tives and has concluded that the recommendations made to upgrade the designs
may not have been implemented for all affected Mark I BWRs. Furthermore, a
similar problem of inadequate separation for controls and safety classifi-
cation also may exist in the suppression chamber-to-reactor building vacuum
relief system for Mark II BWRs.
No specific action or written response is required by this information
notice; however, contingent upon the results of further staff evaluation, a
Bulletin or a Generic Letter requesting specific licensee actions may be
issued. If you have any questions about this matter, please contact the Re-
gional Administrator of the appropriate NRC regional office or this office.
Edward L. Jordan, Director
Division of Emergency Preparedness
and Engineering Response
Office of Inspection and Enforcement
Technical Contact: R. N. Singh, IE
(301) 492-8985
Attachment: List of Recently Issued IE Information Notices
