RBG-26713, Ro:On 870919,valve Manipulations Providing Open Path from Containment Bldg to Condensate Storage Tank Resulted in Reduced Water Level.Caused by Inadequate Procedural Control. Water Level Restored & Procedure SOP-0091 Revised

Ro:On 870919,valve Manipulations Providing Open Path from Containment Bldg to Condensate Storage Tank Resulted in Reduced Water Level.Caused by Inadequate Procedural Control. Water Level Restored & Procedure SOP-0091 Revised

ML20235Q190
Person / Time
Site:	River Bend
Issue date:	09/29/1987
From:	Booker J GULF STATES UTILITIES CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
RBG-26713, NUDOCS 8710070522
Download: ML20235Q190 (4)

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G UI,F STATES ' UTIIsITIES COMI'ANY Alvf R BEND STADON POST OFFICE BOX 220 ST FRANCISVILLL LOUISLANA 70776 AREA CODE 604 635 60!i4 346 8651 September 29, 1987 RBG -26713 File No. G9.25.1.4, G15.4.1 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555 Gentlemen:

River Bend Station - Unit 1 Docket'No. 50-458 )

l l Please find enciesed a voluntary-report describing a condition which was recently identified during an outage concerning valve manipulations on the fuel pool cooling system which provided an open path from the Containment Building upper fuel pool to the condensate storage tank. If you have any further questions, please contact Mr. Rick J. King at (504)381-4146.

Sincerely,

. F.Sk &y J. E. Booker Manager-River Bend Oversight River Bend Nuclear Group (J

JEB/ ERG /TFP/DDWh /ch Enclosure cc: U.S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive, Suite.1000 Arlington, TX 76011 NRC Resident Inspector Post Office Box 1051 St. Francisville, LA 70775 8710070522 070929 PDR ADOCK 05000458 l 5 PDR $ i 13 1

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, . I REPORTED CONDITION On September 19, 1987, with the plant in the Refueling Mode, River Bend Station (RBS) Operations personnel removed and transported the steam dryer assembly from the reactor pressure vessel (RPV) to its laydown area in the Containment Building upper pool adjacent to the upper pool spent fuel storage rack area. The upper fuel pool was isolated from the reactor cavity. No spent fuel had been removed from the RPV and no spent fuel was j being stored in the containment (upper) fuel pool. Water level in the l upper pool had been reduced approximately two feet below normal level to compensate for any surge in water level due to submergence of the steam dryer assembly in the pool. The main control room upper pool water level instruments were reading downscale prior to and following movement of the steam dryer assembly. The upper fuel pool water was being recirculated for cleanup via the fuel pool purification pumps. At approximately 0300 hours0.00347 days <br />0.0833 hours <br />4.960317e-4 weeks <br />1.1415e-4 months <br /> on September 20, 1987, an operator was dispatched to transfer the fuel pool purification system suction from the recirculation mode to the condensate i storage tank (CST) to provide water inventory makeup. Station Operating Procedure (SOP)-0091, " Fuel Pool Cooling and Cleanup", was utilized for manual valve lineup for makeup from the CST. The SOP required the operator to monitor upper pool level closely via control room instrumentation to l avoid overfilling. Valve sequencing was performed as follows: 1) The CST l 1selation valve to the Fuel Fool Purification System was first opened (ISFC-V57), 2) The CST makeup valve to the Fuel Pool Purification System (ISFC-V232) was opened. This configuration provided a passage directly from the containment building upper spent fuel pool directly to the CST via an open containment pool outlet valve (1SFC-V136). The operator was not aware of the reduction in upper pool water level during the initial valve manipulation. The next step was to isolate the containment pool outlet valve (ISFC-V136); however, this was not performed immediately.

CSU has concluded that the root cause of this event is attributed to inadequate procedural controls as to the potential impact of valve sequencing in the procedure.

EVALUATION AND CORRECTIVE ACTION At approximately 0320 hours0.0037 days <br />0.0889 hours <br />5.291005e-4 weeks <br />1.2176e-4 months <br />, the Auxiliary Control Room Operator notified l the main control room operator of the increasing CST water level. A l radiation protection technician evacuated the refueling floor area inside the Containment Building due to the local radiation monitors indicating l

increasing radiation Icvels (beacon and/or alarm) and commenced to spray the steam dryer assembly to reduce airborne radioactivity. An increase in radiation levels was observed in the main control room via the Digital Radiation Monitoring System (DRMS) Alarms. The levels recorded on DRMS reached approximately 92 mrem /hr in the containment upper pool area. During this time the operator closed ISFC-V136, thus terminating the level reduction and commencing the refilling of the pool. Water level was restored at 0555 hours0.00642 days <br />0.154 hours <br />9.176587e-4 weeks <br />2.111775e-4 months <br />.

Upon further review, anti-siphoning devices in the upper containment pool outlet ifne were determined to be defeated due to installed' plugs. When the anti-siphoning device plugs are removed, the anti-siphoning device is designed to maintain a minimum of 10 feet of water above the top of the spent fuel racks. The outage schedule had previously been revised to reflect removal of the anti-siphoning device plugs prior to implementation  ;

of the appropriate fuel handling procedure for fuel movement. l The following corrective actions are being taken.

1. Prior to moving spent fuel, CSU will rewrite SOP-0091, with restrictions on fuel movement while performing valve manipulations, to ' enhance sequencing of valves and provide necessary cautions. Also, administrative controls for local monitoring of any fuel pool ;

manipulations will be provided. In addition, the procedure will be verified by operation of the system. A Standing Order has been issued to restrict handling of irradiated fuel during any fuel pool cooling  !

system realignments. Normal steady state operation, including all pool I levels, is now required to be verified prior to resuming _ irradiated fuel moves.

2. The anti-siphoning device plugs were removed and procedures are being revised to positively control the installation of the plugs. Normal I operation will be with the plugs removed to ensure proper functioning of I

anti-siphoning devices.

3. During Refueling Outage 1, while fuel is stored in the upper pool, GSU will verify hourly (locally) the upper pool level while maintaining the  ;

level in the normal band with alarms cleared (not alarming) in the main

' Control Room. If the level is not in the normal band and a low or high '

level alarm sounds, a continuous watch will be conducted at the upper fuel pool until level is returned to the normal band.

4. Other potential pathways are being reviewed where pool-to-pool or pool-to-sink interfaces exist to ensure valving configurations are i considered and controlled via procedural changes with cautions and verifications.

5. Training on all revised procedures related to this event will be conducted for those individuals using the procedures prior to their use.

6. Prior to storage of fuel in the lower fuel pool, CSU will drill a redundant anti-siphon hole in the suction line that has the removable anti-siphon plug in the fuel pool purification system (line #006-2-3 from P&ID 34-2A). The hole should be at ~least 10 feet above the top of the fuel racks.

7. GSU has demonstrated that all anti-siphoning devices are clear of blockage.

8. Soon after Refueling Outage 1, a redundant anti-siphon hole in the upper fuci pool suction line will be drilled at least 10 feet above the top of the fuel racks (line'#008-68-3 from P&ID 34-2A).

SAFETY ASSESSMENT For the specific path through the 6-inch diameter pipe, a calculation on the reduction in level as a function of time determined that without operator action, water level would have been maintained above the top of active fuel in the spent fuel storage racks (had any been in storage) for greater than 90 minutes. The outage schedule had previously been revised to reflect removal of the anti-siphoning device plugs prior to implementation of the appropriate fuel handling procedure. for fuel movement. During normal  ;

refueling conditions for fuel movement, this makeup system configuration would not be procedurally allowed but instead a low volume hose would be utilized for makeup requirements. Other makeup paths / systems are also available. With normal water level instrumentation on scale, the water level in the upper pool would be at its normal level of at least 23 feet of water maintained over the top of irradiated fuel assemblies seated in the upper containment fuel pool racks, as required by the RBS Technical Specifications (Section 3/4.9.9). With minimum water level requirements not maintained, suspension of all fuel movement and crane operations are required. Under the existing conditions, at no time was there any impact on the safe operation of the plant or to the health and safety of the public. ,

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