Information Notice No. 80-37: Containment Cooler Leaks and Reactor Cavity Flooding at Indian Point Unit 2

                                                       SSINS No.:  6835 
                                                       Accession No.: 
                                                       IN 80-37 

                               UNITED STATES 
                           WASHINGTON, D.C. 20555 
                              October 24, 1980 

                                   CAVITY FLOODING AT INDIAN POINT UNIT 2 

Discription of Circumstances: 

This Notice contains information regarding multiple service water leaks into
containment with resulting damage to reactor instrumentation and potential 
damage to the reactor pressure vessel. 

Upon containment entry on October 17, 1980 at Indian Point Unit 2, to repair
a malfunctioning power range nuclear detector, it was discovered that a 
significant amount of water was collected (approximately 100,000 gal) on the
containment floor, in the containment sumps, and in the cavity under the 
reactor pressure vessel (RPV). This collected water probably caused the 
detector malfunction, and the water in the cavity under the RPV is believed 
to have been deep enough to wet several feet of the pressure vessel lower 
head, causing an unanalyzed thermal stress condition of potential safety 

This condition resulted from the following combination of conditions: (1) 
Both containment sump pumps were inoperable, one due to blown fuses from an 
unknown cause and the other due to binding of its controlling float; (2) The
two containment sump level indicating lights which would indicate increasing
water level over the water level range present in the containment were stuck
(on) and may have been for several days, leaving the operator with no 
operable instrumentation to measure water level in the containment; (3) The 
moisture level indicators in the containment did not indicate high moisture 
levels, apparently because they are designed to detect pressurized hot water
or steam leaks (i.e., a LOCA), and are not sensitive to the lower airborne 
moisture levels resulting from relatively small cold water leaks; (4) The 
hold-up tanks which ultimately receive water pumped from the containment 
sump also receive Unit 1 process water, lab drain water, etc. These other 
water sources masked the effect of cessation of water flows from the Unit 2 
sump; (5) There were significant, multiple service water leaks from the 
containment fan cooling units directly onto the containment floor. These 
coolers have a history of such leakage, which cannot be detected by supply 
inventory losses since the supply system (service water system) is not a 
closed system; (6) The two submersible pumps in the cavity under the Reactor 
Pressure Vessel were ineffective since they pump onto the containment floor 
for ultimate removal by the (inoperable) containment sump pumps. There is no 
water level instrumentation in the cavity under the RPV, nor was there any 
indication outside the containment when these pumps are running. 

The licensee has installed redundant sump level annunciated alarms in the , 
control room and has installed an annunciated alarm in the control room to 
indicate if either submersible pump in the reactor cavity activates. The 
licensee has also repaired the service water leaks, installed guide bushings
on the sump pump control floats to prevent their binding, and has repaired 
the containment sump water level indicators. 

                                                       IN 80-37 
                                                       October 24, 1980  
                                                       Page 2 of 2 

The licensee plans in the longer term to replace the containment fan unit 
cooling coils. 

It is anticipated that results of a continuing NRC investigation into this 
incident will result in issuance of an IE Bulletin and/or an NRR Generic 
Letter in the near future which will recommend or require specific licensees
and applicant actions. In the interim, we recommend that all licensee 
ascertain that the potential does not exist for undetected water 
accumulation in the containment. 

This Information Notice is provided to inform licensees of a possibly 
significat matter. No written response to this Information Notice is 


Page Last Reviewed/Updated Thursday, March 25, 2021