Information Notice No. 88-65: Inadvertent Drainages of Spent Fuel Pools
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555
August 18, 1988
Information Notice No. 88-65: INADVERTENT DRAINAGES OF SPENT FUEL POOLS
All holders of operating licenses or construction permits for nuclear power
reactors and fuel storage facilities.
This information notice is being provided to alert addressees to potential
problems resulting from unintentional draining of spent fuel pools (SFPs). 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
Description of Circumstances:
Wolf Creek - On December 22, 1987 the licensee, Kansas Gas and Electric, un-
intentionally lowered the level of water in the SFP to an estimated minimum
height of 22 feet above the stored fuel. The licensee determined that a valve
in the return line to the refueling water storage tank (RWST) had been
inadvertently left open two days earlier after operations to clean up the RWST
inventory through the SFP clean up system. The licensee stopped the drainage
by closing this valve.
The safety-related area radiation monitors near the SFP did not alarm. In the
control room, the SFP level indicator and the low level alarm on the SFP
cooling system pump suction were both inoperable. The control room operators
were alerted to this event by the successive tripping of SFP cooling system
pump A while they were operating the SFP clean up system.
River Bend - On September 20, 1987 the licensee, Gulf States Utilities, while
preparing for refueling, intentionally lowered the level in the upper SFP to 2
feet below the normal level of 185 feet to allow for the expected water dis-
placement when the steam dryer assembly would be transferred there. This
caused the level indicator in the control room to go off scale as expected and
the related low level alarm to activate as expected. Pool level indication is
provided for a narrow range: 185 feet � 12 1/2 inches. The alarm is set at
184 feet 7 1/2 inches when the level decreases.
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August 18, 1988
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After placing the steam dryer in the pool, the plant operators opened two
valves from the condensate storage tank (CST) with the intent of then closing
two valves in the SFP purification suction line (see Figure 1). Within 20
minutes, while the four valves were opened, the level decreased an additional
5 feet, partially uncovering the dryer assembly. Safety-related area
radiation monitors at both ends of the pool alarmed and indicated fields of
about 80 mr/hr.
The drainage had been made possible by a procedural sequence establishing a
free flow path in conjunction with a nonredundant antisiphon device (a
vertical vent pipe under water) in the suction line of the SFP purification
system. The antisiphon device had been plugged.
The operator in the control room was not aware of the pool draining because
the level indicator was off scale. At the time of the SFP area radiation
monitor alarms, however, an operator at an auxiliary equipment control panel
noticed a water level increase in the CST. Realizing that this combination of
signals meant the SFP was draining, operators closed the two manual valves in
the SPF purification system suction line to stop the draining. They restored
the level in about 2 hours using one SFP purification pump drawing suction
from the CST.
In addition to the two events discussed above, another partial drainage of the
spent fuel pool occurred at San Onofre 3 on June 22, 1988. Drainage of SFPs
can cause potentially high radiation doses and damage to fuel elements result-
ing from the uncovery of spent fuel in storage or, in particular, in transit.
Although the consequences of the events described in this information notice
were not significant, they indicate deficiencies in control and management of
refueling operations and SFP safety.
At San Onofre, the SFP cooling system design was apparently properly siphon-
protected, but the SFP purification system design apparently was not. At
River Bend, antisiphon devices in the SFP purification system were plugged to
permit preoperational testing but were not unplugged at the beginning of
Operating procedures for the interconnected systems associated with SFPs
either were not sufficiently detailed or were incorrect and failed to prevent
alignments causing unintentional drainage. At River Bend, the range of SFP
level indication was limited. Detailed operating procedures were available
but were not correct. At Wolf Creek, detailed operating procedures did not
Surveillance procedures were not implemented to ensure the operability of all
instrumentation and control equipment. At Wolf Creek, there were no surveil-
lance procedures for water level instrumentation that had been inoperable for
a year. Also, the SFP cooling pump suction alarm was inoperable.
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August 18, 1988
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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 techni-
cal contacts listed below or the Regional Administrator of the appropriate
Charles E. Rossi, Director
Division of Operational Events Assessment
Office of Nuclear Reactor Regulation
Technical Contacts: Vern Hodge, NRR
J. Kudrick, NRR
1. Figure 1. Simplified Flow Path Diagram of Upper Pool
Purification System at River Bend
2. List of Recently Issued NRC Information Notices
. Attachment 2
August 18, 1988
Page 1 of 1
LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information Date of
Notice No._____Subject_______________________Issuance_______Issued to________
88-64 Reporting Fires in Nuclear 8/18/88 All holders of OLs
Process Systems at Nuclear or CPs for nuclear
Power Plants power reactors.
88-63 High Radiation Hazards 8/15/88 All holders of OLs
from Irradiated Incore or CPs for nuclear
Detectors and Cables power reactors,
and test reactors.
88-62 Recent Findings Concerning 8/12/88 All holders of NRC
Implementation of Quality quality assurance
Assurance Programs by program approval
Suppliers of Transport for radioactive
Packages material packages.
88-61 Control Room Habitability - 8/11/88 All holders of OLs
Recent Reviews of Operating or CPs for nuclear
Experience power reactors.
88-60 Inadequate Design and 8/11/88 All holders of OLs
Installation of Watertight or CPs for nuclear
Penetration Seals power reactors.
88-04, Inadequate Qualification 8/9/88 All holders of OLs
Supplement 1 and Documentation of Fire or CPs for nuclear
Barrier Penetration Seals power reactors.
88-59 Main Steam Isolation Valve 8/9/88 All holders of OLs
Guide Rail Failure at or CPs for nuclear
Waterford Unit 3 power reactors.
88-58 Potential Problems with 8/8/88 All holders of OLs
ASEA Brown Boveri ITE-51L or CPs for nuclear
Time-Overcurrent Relays power reactors.
88-57 Potential Loss of Safe 8/8/88 All holders of OLs
Shutdown Equipment Due to or CPs for nuclear
Premature Silicon Controlled power reactors.
OL = Operating License
CP = Construction Permit
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