United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 88-65: Inadvertent Drainages of Spent Fuel Pools

                                  UNITED STATES
                          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


Addressees:

All holders of operating licenses or construction permits for nuclear power 
reactors and fuel storage facilities.

Purpose:

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 
is required.

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.  




8808120327
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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.

Discussion:

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 
refueling operations.

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 
exist.  

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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                                                            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 techni-
cal 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:  Vern Hodge, NRR
                     (301) 492-1169

                     J. Kudrick, NRR
                     (301) 492-0871


Attachments:  
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
                                                            IN 88-65 
                                                            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, 
                                                            research 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. 
               Rectifier Failure 
_____________________________________________________________________________
OL = Operating License
CP = Construction Permit 
Page Last Reviewed/Updated Tuesday, November 12, 2013