Information Notice No. 89-26: Instrument Air Supply to Safety-Related Equipment
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
March 7, 1989
Information Notice No. 89-26: INSTRUMENT AIR SUPPLY TO SAFETY-RELATED
EQUIPMENT
Addressees:
All holders of operating licenses or construction permits for nuclear power
reactors.
Purpose:
This information notice is being provided to alert addressees of instrument
air inadequacies identified by licensees in response to Generic Letter 88-14,
"Instrument Air Supply System Problems Affecting Safety-Related Equipment,"
dated August 8, 1988. It is expected that recipients will review the infor-
mation for applicability to their facilities and consider actions, as appro-
priate, 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 a review of the instrument air supply to safety-related equipment, as
requested by Generic Letter 88-14, the Boston Edison Company, licensee for
Pilgrim Nuclear Power Station, discovered two design inadequacies. These
problems affect the integrity of the secondary containment and the primary
containment.
On December 22, 1988, during leak rate testing of the secondary containment,
the standby gas treatment system was unable to achieve the 0.25-inch water
vacuum required by the technical specifications because of in-leakage of
outside air past the inner door of the reactor building trucklock (RBTL).
The test was being conducted with revised procedures as a result of the
review requested by Generic Letter 88-14. The new procedures required the
test to be conducted with the RBTL outer door open and the RBTL inner door
closed, but with the inner door's inflatable seal deflated. Since the plant
began operating in 1972, previous leak rate testing had been performed with
the inner door seal inflated by the non-safety-related instrument air system
and with the non-seismically qualified RBTL outer door closed.
8903010207
. IN 89-26
March 7, 1989
Page 2 of 3
The licensee's corrective action involved installing a non-inflatable-type
rubber gasket to the RBTL inner door frame, which allowed subsequent successful
completion of the leak rate test.
The same problem of relying on the non- safety-related instrument air system
to inflate seals on doors to maintain the integrity of the secondary contain-
ment was identified at Vermont Yankee Nuclear Power Station and Fermi Atomic
Power Plant, Unit 2, on January 4, 1989, and February 8, 1989, respectively.
The second design inadequacy at the Pilgrim station was discovered on
January 10, 1989. The containment isolation valves in the torus-to-reactor
building vacuum breaker lines, which are redundant to the torus vacuum
breakers, use instrument air pressure to maintain the valves in the closed
position. Upon loss of air pressure, these valves are designed to open to
allow the vacuum breakers to perform their safety function of preventing
containment implosion. When the valves fail open, the isolation function
of the valves is lost. At Pilgrim the design requires an adequate supply
of air pressure to the vacuum breaker isolation valves for 30 days if the
instrument air system fails. The licensee for Pilgrim determined by a test
that the air supply provided by the safety-related accumulators would be
depleted in less than 1 hour, resulting in the loss of one of the two con-
tainment isolation barriers. To correct this situation, the licensee
installed additional larger qualified accumulators and a qualified air line
that connects to pressurized air bottles. Portable air bottles can be
connected to the air line to provide adequate air pressure if needed for the
long term requirement. The licensee also instituted surveillance to ensure
that acceptable accumulator air pressure will be maintained for at least 24
hours.
Similar problems involving the use of non-safety-related instrument air
systems affecting the integrity of the primary containment have been
discovered at Oyster Creek Nuclear Power Plant on February 8, 1989, and at
Browns Ferry Nuclear Power Station, Units 1, 2, and 3, on January 31, 1989.
At Oyster Creek, the licensee determined that the air accumulators to the main
steam isolation valves would rapidly depressurize if the normal
non-safety-related air supply was interrupted. At Browns Ferry, the
instrument air system would be relied on without accumulators during a
design-basis accident to provide the air pressure for the containment
isolation valves in the suppression pool vacuum relief lines to maintain the
valves in the closed position.
. IN 89-26
March 7, 1989
Page 3 of 3
No specific action or written response is required by this information
notice. If you have any questions about this matter, please contact one of
the technical contacts 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 Contacts: T. Silko, AEOD
(301) 492-9059
T. Greene, NRR
(301) 492-1176
J. Lyash, RI
(215) 337-5132
Attachment: List of Recently Issued NRC Information Notices
. Attachment
IN 89-26
March 7, 1989
Page 1 of 1
LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
_____________________________________________________________________________
Information Date of
Notice No._____Subject_______________________Issuance_______Issued to________
89-25 Unauthorized Transfer of 3/7/89 All U.S. NRC source,
Ownership or Control of byproduct, and
Licensed Activities special nuclear
material licensees
89-24 Nuclear Criticality Safety 3/6/89 All fuel cycle
licensees and other
licensees
possessing more
than critical
mass quantities of
special nuclear
material.
89-23 Environmental Qualification 3/3/89 All holders of OLs
of Litton-Veam CIR Series or CPs for nuclear
Electrical Connectors power reactors.
89-22 Questionable Certification 3/3/89 All holders of OLs
of Fasteners or CPs for nuclear
power reactors.
89-21 Changes in Performance 2/27/89 All holders of OLs
Characteristics of Molded- or CPs for nuclear
Case Circuit Breakers power reactors.
88-73, Direction-Dependent Leak 2/27/89 All holders of OLs
Supplement 1 Characteristics of Contain- or CPs for nuclear
ment Purge Valves power reactors.
89-20 Weld Failures in a Pump 2/24/89 All holders of OLs
of Byron-Jackson Design or CPs for nuclear
power reactors.
89-19 Health Physics Network 2/23/89 All holders of OLs
or CPs for nuclear
power reactors, and
the following fuel
facilities:
Nuclear Fuel
Services of Erwin,
General Atomic, UNC
Montville, B&W LRC
Lynchburg, and B&W
Lynchburg.
_____________________________________________________________________________
OL = Operating License
CP = Construction Permit
..
Page Last Reviewed/Updated Friday, May 22, 2015