Information Notice No. 80-37: Containment Cooler Leaks and Reactor Cavity Flooding at Indian Point Unit 2
SSINS No.: 6835
Accession No.:
8008220249
IN 80-37
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
October 24, 1980
Information Notice No. 80-37: CONTAINMENT COOLER LEAKS AND REACTOR
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
significance.
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.
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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
required.
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