U.S. Nuclear Regulatory Commission
                             Operations Center
 
                             Event Reports For
                            09/30/96 - 10/01/96
 
                             ** EVENT NUMBERS **
 
31076  

+----------------------------------+              +-----------------------+     
|POWER REACTOR                     |              |EVENT NUMBER:  31076   |     
+----------------------------------+              +-----------------------+     
+------------------------------------------------+-----------------------------+
|FACILITY: ROBINSON                   REGION:  2 |NOTIFICATION DATE: 09/30/96  |
|UNIT:     [2] [ ] [ ]                 STATE: SC |NOTIFICATION TIME: 18:25 [ET]|
|RX TYPE: [2] W-3-LP                             |EVENT DATE:        09/30/96  |
+------------------------------------------------+EVENT TIME:        16:00[EDT]|
|NRC NOTIFIED BY: JAN KOZYRA                     |LAST UPDATE DATE:  09/30/96  |
|HQ OPS OFFICER:  LEIGH TROCINE                  +-----------------------------+
+------------------------------------------------+       NOTIFICATIONS         |
|EMERGENCY CLASS: NOT APPLICABLE                 +-----------------------------+
|10 CFR SECTION:                                 |MILTON SHYMLOCK       RDO    |
|AIND 50.72(b)(2)(iii)(D) ACCIDENT MITIGATION    |                             |
|                                                |                             |
|                                                |                             |
|                                                |                             |
|                                                |                             |
+-----+----------+-------+--------+--------------+--+--------+-----------------+
|UNIT |SCRAM CODE|RX CRIT|INIT PWR|  INIT RX MODE   |CURR PWR|  CURR RX MODE   |
+-----+----------+-------+--------+-----------------+--------+-----------------+
|  2  |   N          N        0     REFUELING       |     0    REFUELING       |
|     |                                             |                          |
|     |                                             |                          |
+-----+---------------------------------------------+--------------------------+

                                   EVENT TEXT
+------------------------------------------------------------------------------+
| DETERMINATION THAT FLOATING DEBRIS RESULTING FROM A LOSS OF COOLANT          |
| ACCIDENT (LOCA) COULD BECOME WATER LOGGED AND SUBJECT THE EMERGENCY CORE     |
| COOLING SYSTEM (ECCS) SUMP SCREENS TO CLOGGING AND IDENTIFICATION OF GAPS    |
| IN THE ECCS SUMP SCREENS                                                     |
|                                                                              |
| WITH UNIT 2 DEFUELED, THE LICENSEE PERFORMED AN ENGINEERING EVALUATION TO    |
| RESOLVE INCONSISTENCIES BETWEEN ENGINEERING INFORMATION AND THE UNIT 2       |
| UPDATED FINAL SAFETY ANALYSIS REPORT (UFSAR) REGARDING THE ESTIMATED HIGH    |
| CONTAINMENT WATER LEVEL IN THE EVENT OF A LOCA.  AT ROBINSON, THE ECCS IS    |
| COMPRISED OF THE RESIDUAL HEAT REMOVAL (RHR) SYSTEM, SAFETY INJECTION (SI)   |
| ACCUMULATORS, AND THE HIGH HEAD SI SYSTEM. THE EVALUATION DETERMINED THAT    |
| WHEN THE REFUELING WATER STORAGE TANK IS AT THE LOWEST LEVEL, THE RESULTING  |
| WATER LEVEL IN CONTAINMENT IS IN EXCESS OF THE BAFFLES IN THE SUMP AREA      |
| WHICH ARE DESIGNED TO EXCLUDE FLOATING DEBRIS FROM THE ECCS SUMP.            |
| CONSEQUENTLY, THE LICENSEE BELIEVES THAT FLOATING DEBRIS RESULTING FROM A    |
| LOCA CAN SUBSEQUENTLY BECOME WATER LOGGED AND THEN SUBJECT THE ECCS SUMP     |
| SCREENS TO CLOGGING.  IF THE ECCS SUMP SCREENS ARE SUFFICIENTLY CLOGGED      |
| DURING THE RECIRCULATION PHASE OF A POSTULATED LOCA, INADEQUATE NET          |
| POSITIVE SUCTION HEAD FOR THE RHR PUMPS, AND SUBSEQUENT FAILURE OF THE RHR   |
| PUMPS COULD RESULT.  (THE RHR PUMPS ARE UTILIZED FOR LONG-TERM LOW PRESSURE  |
| COOLING OF THE CORE AFTER A POSTULATED LOCA.)                                |
|                                                                              |
| IN ADDITION, UFSAR SECTION 6.3.2.2.2 STATES THAT THE ECCS SUMP SCREENS ARE   |
| DESIGNED TO RESTRICT PARTICLES GREATER THAN 7/32" IN THE LARGEST DIMENSION   |
| TO PRECLUDE CLOGGING OF THE CONTAINMENT SPRAY SYSTEM SPRAY NOZZLES WHICH     |
| HAVE A CIRCULAR DIAMETER OF 3/8" AS STATED IN UFSAR SECTION 6.5.2.2.  AN     |
| EARLIER INSPECTION OF THE ECCS SUMP SCREENS FOUND GAPS LARGER THAN THE       |
| UFSAR SPECIFIED 7/32" IN THE LARGEST DIMENSION.  DISCREPANCIES HAVE ALSO     |
| BEEN FOUND BETWEEN THE UFSAR DESCRIPTION OF THE SCREENS AND THE INSTALLED    |
| SCREENS.  BECAUSE THE INSTALLED SCREENS ARE NOT IN ACCORDANCE WITH THE       |
| UFSAR SPECIFICATIONS AS WRITTEN AND BECAUSE NO PRIOR EVALUATION OF           |
| ACCEPTABILITY OF THE SCREENS IN THEIR CURRENT CONDITION COULD BE FOUND, THE  |
| LICENSEE DETERMINED THAT THE PAST OPERABILITY OF THE CONTAINMENT SPRAY       |
| SYSTEM AS WELL AS OTHER ECCS SYSTEMS THAT TAKE SUCTION FROM THE ECCS SUMP    |
| IN THE RECIRCULATION MODE (I.E., RHR AND SI SYSTEMS) CANNOT BE ASSURED AT    |
| THIS TIME.                                                                   |
|                                                                              |
| ACCORDINGLY, DUE TO THE POTENTIAL FOR RENDERING THE VARIOUS PORTIONS OF THE  |
| ECCS AND CONTAINMENT SPRAY SYSTEMS INOPERABLE DURING THE POST-LOCA           |
| RECIRCULATION MODE, THE LICENSEE DETERMINED THIS EVENT TO BE REPORTABLE AS   |
| A CONDITION THAT ALONE COULD HAVE PREVENTED THE FULFILLMENT OF A SAFETY      |
| FUNCTION THAT IS NEEDED TO MITIGATE THE CONSEQUENCES OF AN ACCIDENT.  THIS   |
| DETERMINATION WAS MADE AT 1600 ON SEPTEMBER, 30, 1996.                       |
|                                                                              |
| THE LICENSEE NOTIFIED THE NRC RESIDENT INSPECTOR.                            |
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