United States Nuclear Regulatory Commission - Protecting People and the Environment

IEB 80-24 Prevention of Damage Due to Water Leakage Inside Containment (Generic Letter 80-98)

                                                            SSINS No.:  6820
                                                            Accession No.: 
                                                            IEB 80-24 
                                 UNITED STATES 
                           WASHINGTON, D.C.   20555 

                               November 21, 1980 

                        CONTAINMENT (OCTOBER 17, 1980 INDIAN POINT 2 EVENT) 

Description of Circumstances: 

On October 24, 1980 IE Information Notice No. 80-37 described an event that 
occurred at the Indian Point Unit 2 (IP-2) facility.  On October 17, 1980, 
upon containment entry for repair to a nuclear instrument, it was discovered
that several inches of water had accumulated on the containment floor 
without the operator's knowledge.  This accumulation was later determined to 
have amounted to over 100,000 gallons which flooded the reactor  vessel pit 
and wetted the lower nine feet of the reactor vessel while the reactor was 
at operating temperature. 

The flooded condition resulted from the following combination of conditions: 
(1)  There were significant multiple service water leaks from piping and fan
coolers onto the containment floor.  This system had a history of leakage; 
(2)  Both containment sump pumps were inoperable, one due to blown fuses and
the other due to binding of its float switch; (3)  The significance of two 
containment sump level indicating lights which indicated that the water 
level was continuously above the pump-down level was not recognized by the 
operators; (4)  There was no high water level alarm and the range of sump 
level indicating lights failed to indicate the overflowing sump level; (5)  
The moisture level indicators for the containment atmosphere did not 
indicate  high moisture levels, apparently due to an error in calibration 
and/or ranging which make them insensitive  to the moisture levels resulting 
from relatively small cold water leaks; (6)  The hold-up tanks which 
ultimately receive water pumped from the containment sump also received 
water from other sources (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; (7)  The fan cooler condensate weir level measuring 
instruments were not properly calibrated; (8)  There was no water level 
instrumentation in the reactor vessel pit and the pumps were ineffective 
since they discharge to the containment floor for ultimate removal by the 
containment sump pumps. 

This Bulletin is issued to enable the NRC staff to formulate requirements 
for long term generic corrective actions which will be the subject(s) of 
future NRC actions.  The bulletin requires short term actions which will 
preclude IP-2 type events at other plants in the interim before actions 
which will be the subject(s) of future type events at other plants in the 
interim before the longer term generic actions are accomplished. 

                                                         IEB 80-24 
                                                         November 21, 1980 
                                                         Page 2 of 3 

Actions to be Taken by Licensees: 

1.   Provide a summary description of all open* cooling water systems 
     present inside containment.  Your description of the cooling water 
     systems must include:  (a) Mode of operation during routine reactor 
     operation and in response to a LOCA; (b)  Source of water and typical 
     chemical content of water; (c)  Materials used in piping and coolers; 
     (d)  Experience with system leakage; (e)  History and type of repairs 
     to coolers and piping systems (i.e., replacement, weld, braze, etc.); 
     (f)  Provisions for isolating portions of the system inside containment 
     in the event of leakage including vulnerability of those isolation 
     provisions to single failure; (g)  Provisions for testing isolation 
     valves in accordance with Appendix J to 10 CFR 50 (h)  Instrumentation 
     (pressure, dew point, flow, radiation detection, etc.) and procedures 
     in place to detect leakage; and (i) Provisions to detect radioactive 
     contamination in service water discharge from containment. 
2.   For plants with open cooling water systems inside containment take the 
     following actions: 

     a.   Verify existence or provide redundant means of detecting and 
          promptly alerting control room operators of a significant 
          accumulation of water in containment (including the reactor vessel
          pit if present). 

     b.   Verify existence or provide positive means for control room 
          operators to determine flow from containment sump(s) used to 
          collect and remove water from containment. 

     c.   Verify or establish at least monthly surveillance procedures, with
          appropriate operating limitations, to assure plant operators have 
          at least two methods  of determining water level in each location 
          where waste may accumulate.  The surveillance procedures shall 
          assure that at least one method to remove water from each such 
          location is available during power operation.  In the event either 
          the detection or removal systems become inoperable it is 
          recommended that continued power operation be limited to seven 
          days and added surveillance measures be instituted. 

* An Open system utilizes an indefinite volume, such as a river, so that 
leakage, from the system could not be detected by inventory decrease.  In 
addition, a direct radioactive pathway might exist to outside containment in
the event of a LOCA simultaneous with a system leak inside containment.  A 
closed system utilizes a fixed, monitored volume such that leakage from the 
system could be detected from inventory decrease and a second boundary 
exists to prevent loss of containment integrity as a result of a system leak 
inside containment. 

                                                         IEB 80-24 
                                                         November 14, 1980 
                                                         Page 3 of 3 

     d.   Review leakage detection systems and procedures and provide or 
          verify ability to promptly detect water leakage in containment, 
          and to isolate the leaking components or system.  Periodic 
          containment entry to inspect for leakage should be considered. 
     e.   Beginning within 10 days of the date of this bulletin, whenever 
          the reactor is operating and until the measures described in (a) 
          through (d) above are implemented, conduct interim surveillance 
          measures. The measures shall include where practical (considering 
          containment atmosphere and ALARA considerations) a periodic 
          containment inspection or remote visual surveillance to check for 
          water leakage. 
          If containment entry is impractical during operation, perform a 
          containment inspection for water leakage at the first plant 
          shutdown for any reason subsequent to receipt of this bulletin. 
     f.   Establish procedures to notify the NRC of any service water system
          leaks within containment via a special licensee event report (24 
          hours with written report in 14 days) as a degradation of a 
          containment boundary. 

3.   For plants with closed cooling water systems inside containment provide 
     a summary of experiences with cooling water system leakage into 

4.   Provide a written report, signed under oath or affirmation, under the 
     provisions of Section 182a of the Atomic Energy Act of 1954, in 
     response to the above items within 45 days of the date of this 
     bulletin. Include in your report where applicable, your schedule for 
     completing the actions in response to items 2 (a) through (d).  Your 
     response should be sent to the Director of the appropriate Regional 
     Office with a copy forwarded to the Director, NRC, Office of Inspection 
     and Enforcement, Washington, D.C. 20555. 
If you desire additional information regarding this matter please contact 
the appropriate IE Regional Office. 

Approved by GAO, B180225 (R0072); clearance expires November 30, 1980. 
Approval was given under a blanket clearance specifically for identified 
generic problems.

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