Information Notice No. 84-39: Inadvertent Isolation of Containment Spray Systems
SSINS No.: 6835
IN 84-39
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
May 25, 1984
Information Notice No. 84-39: INADVERTENT ISOLATION OF CONTAINMENT SPRAY
SYSTEMS
Addressees:
All pressurized water power reactor facilities holding an operating license
(OL) or construction permit (CP).
Purpose:
This information notice is provided to alert licensees and applicants of the
potential for significant degradation of safety associated with the
inadvertent isolation of containment spray. Recipients are expected to
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 and, therefore, no specific action or written
response is required.
Description of Circumstances:
Farley Unit 2 Farley Unit 2 was taken to cold shutdown on October 24, 1982,
to begin a refueling and maintenance outage. On October 28, 1982, while
aligning valves for certain scheduled inservice inspections, the licensee
found the containment spray header isolation valve on each of the two supply
headers locked in the closed position. These valves, located inside the Unit
2 containment building, supply separate, redundant, containment spray rings.
After investigation and record searches of valve movement documentation, the
licensee concluded that the valves had been closed since before the plant
achieved initial criticality on May 8, 1981. Thus the redundant, containment
spray systems were inoperable during this period and consequently would have
been unable to fulfill their safety function.
The event was caused by the valves not being in conformance with design
draw-ings and by the inadequacy of the procedure used by an operator to
determine the position of the valves. A unique condition developed in these
valves when the vendor, Westinghouse, made a design change that lengthened
the valve stem to increase the valve's adaptability to a motor-operated
valve (however, the motors to operate the valves were never installed and
the valves remained manually operated). The design change resulted in a
valve stem that makes the valve appear to be open when it is actually
closed. That is, the extra long valve stem shows 6 inches of threaded stem
extending out of the bonnet when the valve is in the closed position.
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IN 84-39
May 25, 1984
Page 2 of 5
Therefore, operators, who were instructed and trained to observe valve stem
position to verify the valve positions, erroneously interpreted these valves
as being open when they were, in fact, closed.
Indian Point Unit 2
On November 29, 1983, while the licensee was performing a bimonthly (every
two months) containment spray pump surveillance test during normal
operation, two motor-operated spray header isolation valves were found in
the locked closed, de-energized position instead of the required locked
open, de-energized position. This condition would have prevented automatic
actuation of the containment spray system during the safety injection phase
of an accident.
A review of conditions leading up to this event revealed that on October 12,
1983, during a cold shutdown, these valves were closed and tagged out of
service so that work could be performed on the reactor coolant system. On
October 18, 1983, while still in the cold shutdown condition, the tagout was
cleared even though these valves were specified to remain closed to block
the containment spray paths while personnel continued to work in the
containment. Before plant startup, operators were assigned to complete a
Safety Injection System Check-Off List (COL-12), which should have returned
the valves to their proper positions before heating the reactor coolant
system above 350 degrees.
COL-12 was performed on October 23 and 24, 1983. It required one operator to
ensure the correct valve position and a second operator to verify the posi-
tion. COL-12 directs the operators to the motor control centers to perform
two verifications for each valve: (1) verify that the position of the valve
is open and (2) verify that the breaker is de-energized. In the de-energized
condition, position indication for the valve is lost at the motor control
centers. Verifying position at the motor control center, therefore, requires
energizing the breaker. The first operator assumed that the valve was posi-
tioned by another operator. The second operator assumed the valve was open
because the breaker was locked in the de-energized position.
San Onofre Unit 3
On March 17, 1984, during routine surveillance at approximately 100% power,
manual isolation valves in both of the containment spray headers were found
closed, rendering both trains of the containment spray system (CSS) inoper-
able. Misalignment of the isolation valves was caused by improper use of the
valve alignment checklist for the CSS when leaving the shutdown cooling
mode.
Unit 3 entered Mode 4 (hot shutdown) following an extended surveillance and
maintenance outage on February 27, 1984. The valve alignment checklist was
completed and verified by two operators for the CSS on February 28, which
confirmed the spray header isolation valves to be open as required for CSS
operability in Modes 1-3.
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IN 84-39
May 25, 1984
Page 3 of 5
Because of the inoperability of a safety injection system (SIS) valve, Unit
3 re-entered Mode 5 (cold shutdown) on February 23. Valve alignments were
completed for operation of the shutdown cooling system, including closure of
the containment spray header isolation valves. Valve repairs were completed
for the SIS valve and Unit 3 again entered Mode 4 and left shutdown cooling
on March 2, 1984.
Instead of reperforming the entire CSS valve alignment checklist completed
on February 28, the cognizant control room supervisor, a senior reactor
operator (SRO), designated valves on the completed February 28 checklist to
be repositioned and double-verified. At San Onofre an SRO was permitted to
designate a portion of a checklist to be performed when changes in system
status do not require the entire checklist to be performed.
Double-verifications were conducted in this instance for which of the valves
designated, as required. This repositioning was completed before entry into
Mode 3 on March 4, 1984. However, because of an oversight by the SRO, the
containment spray header isolation valves were not designated to-be
repositioned, and they remained closed until March 17, 1984.
Other Events
The staff has observed other events where procedural or personnel errors
would have prevented operation of the containment spray systems. While most
of these events only resulted in system inoperability for a few minutes or
hours, the potential was there for extended plant operation with these
safety systems inoperable. In addition to the containment spray system, the
following events include examples of inadvertent valving out of the chemical
addition tank. The following is a partial list of both types of events:
Davis-Besse
On January 12, 1978, both containment spray pumps were found with the
circuit breakers de-energized. Personnel error resulted in 24 hours of plant
operation (Mode 4) with the system inoperable.
D.C. Cook Unit 2
On May 2, 1978, during change from Mode 5 to Mode 4, containment spray pumps
remained inoperable when control switches were left in the locked out posi-
tion. Procedural and personnel error left the system inoperable for 4 hours.
Davis Besse
On December 28, 1978, 2 hours after entering Mode 4, containment spray pump
motor breakers were found in the locked out position. This was caused by an
operator failing to follow procedures.
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IN 84-39
May 25, 1984
Page 4 of 5
Indian Point Unit 2
On September 24, 1980, both containment spray,pump control switches were
found in the pull-to-lock position by the resident inspector while the plant
was at full power. Plant procedures called for disabling the containment
spray during containment entry. The licensee was informed of noncompliance,
with Technical Specifications which require the operability of containment
spray when the plant is at power, and the procedures were subsequently
revised.
Point Beach Unit 1
On June 21, 1981, while performing periodic surveillance, the spray additive
tank isolation valve was found in the closed position, thus preventing in-
jection of NaOH to the containment spray system. Operator error left the
valve misaligned for 4 days.
Farley Unit 2
On December 26, 1981, while performing surveillance testing, the isolation
valve on the NaOH spray additive tank was found in the closed position. This
was caused by operator error during position alignment checks.
Farley Unit 1
On May 10, 1982, while performing Penetration Room Exhaust and Air
Filtration System Train Operability and Valve Inservice Test, an operator
inadvertently closed the containment spray suction valves from the refueling
water storage tank (RWST). The valves were closed for 7 hours while the
reactor was at power.
Surry Unit 1
On October 16, 1982, isolation valves leading from the chemical addition
tank were found in the closed position. The cause was attributed to
personnel failure to perform valve alignment checks.
Ginna
On June 13, 1983, while changing modes (cold shutdown to hot shutdown), the
containment spray pumps were found in the pull-to-lock position.
Turkey Point Unit 4
On October 4, 1983, a nonlicensed operator assigned to close the spray
header isolation valves on Unit 3 (cold shutdown) inadvertently closed the
identical valves on Unit 4. Unit 4 operated at power with these valves
closed for approximately 50 hours.
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IN 84-39
May 25, 1984
Page 5 of 5
Discussion:
The intent of this information notice is to heighten awareness of industry
to the potential for significant problems involving the inadvertent
isolation of containment spray systems (CSSs). During shutdown conditions
when containment entries are being made, PWR operators find it desirable to
close the manual isolation valves in each spray header and/or put the spray
pump control switches in the pull-to-lock position. These actions prevent
inadvertent containment spray actuation during maintenance and testing
activities. However, when valve l alignment check-off lists are completed
before restart, procedural inadequacies or personnel errors have resulted in
plants going back to power with the isolation valves closed or the pumps in
the pull-to-lock position, thus preventing automatic operation if needed.
The NRC recommends that recipients of this notice review their existing pro-
cedures for locking out and returning containment spray systems to operation
and determine whether any changes to the existing procedures would be desir-
able in light of the information contained herein.
No written response to this information notice is required. If you need
additional information about this matter, please contact the Regional
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 Contacts: Douglas Pickett, NRR
(301) 492-7876
Eric Weiss, IE
(301) 492-4973
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