ML20050Y800
| ML20050Y800 | |
| Person / Time | |
|---|---|
| Site: | 05000000, Indian Point |
| Issue date: | 07/28/1981 |
| From: | ORGANIZATION FOR ECONOMIC COOPERATION & DEVELOPMENT |
| To: | |
| Shared Package | |
| ML19240B432 | List: |
| References | |
| FOIA-81-380 NUDOCS 8204150190 | |
| Download: ML20050Y800 (4) | |
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.,7 JUL 2 81981 No. IRS 21.2 RESTRICTED DIFFUSION RESTREINTE Date of Receipt 25th Mav 1981 Date de Reception Name of nuclear power station Indian Poin. 2 (US) v Nom de la centrale Date of incident 17th October 1980 Date de l' incident Type of reactor pg.!R Type de reacteur Authorized electrical power Niveau de puissance diectrique 873 MWe autorisd First commercial operation Date de mise en service 1973 8204150190 811109 PDR FOIA CONNOR 81-380 PDR 4765
Significant Floodino of Reactor Containment Building Appendix A (Example 11 of "For All Licensees") of this report notes that serious deficiency in management or procedural controls in major areas can be considered an abnormal occurrence.
In addition, Appendix A (Example 4 of "For Commercial Nuclear Power Plants") of this report notes that discovery of a major condition not specifically considered in the Safety Analysis Report (SAR) or Technical Specifications that requires immediate remedial action can be considered an abnormal occurrence.
(As described below, the licensee took exception to certain of the NRC findings, iricluding the issues pertaining to management controls.)
Date and Place - On October 17, 1980, a significant amount of water was discovered inside the containment building at Consolidated Edison Company's Indian Point Unit 2 facility.
Indian Point Unit 2 utilizes S pressurized water reactor and is located in Westchester County, New York.
Nature and Probable Consequences - Upon entry into the Unit 2 containment build-ing on October 17, 1980, to repair a malfunctioning power range nuclear detector, a significant amount of water was discovered on the containment floor, in the containment sumps, and in the cavity under the reactor pressure vessel.
The amount of water which had accumulated was later determined to be about 125,000 gallons. The source of the water was found to be service water from leaks in service water piping and from leaks in the containment fan cooling units.
Fail-ures and inadequacies of components and systems required to remove and detect water in the containment building resulted in the accumulation of such a large quantity of water without detection.
The floodi.ng directly resulted in the failure of a power range nuclear detector.;
its repair was the original reason for containment building entry.
Because of the flooding, the cavity under the reactor vessel was nearly filled, resulting in the wetting of the lower 9 feet of the reactor vessel and submergence of stainless steel conduits and instrument thimbles located below the reactor vessel.
Although the direct consequences of the event were not significant, the accumu-lation of the large amount of water in containment and the wetting of the reactor vessel raised significant safety questions.
Evaluations to date indicate that there was no damage to the reactor vessel or other components in the reactor vessel cavity; however, continued operation with abnormal conditions that were not known (the undetected accumulation of water in the containment) did represent i
l some degree of decreased safety.
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Cause or Causes - This event resulted from the following combination of conditions:
(1) there were significant multiple service water leaks from the containment r
fan cooling units onto the containment floor. These coolers have a history of such leakage and they cannot be detected by inventory losses since the service water system is an open system supplied from a river; (2) both containment sump pumps were inoperable, one due to blown fuses and the other due to binding of its controlling float switch; (3) a series of containment sump level indicating lights for indicating increasing water level had shown no change for an extended period of time; (4) there was no high water level alarm to indicate the overflow-ing 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 made them insensitive to the moisture levels resulting from relatively small cold water leaks; (6) the two submersible pumps in the cavity under the reactor pressure vessel were ineffective since they pump into the containment sump (and the sump pumps were inoperable); (7) there was no water level instrumentation in the cavity under the reactor vessel; (8) there i
was no indication outside containment that the pumps in the cavity under the reactor vessel were operating; and (9) the holdup tanks which ultimately receive l
water pumped from the containment sump also receive water from other water sources such as Unit 1 process water, lab drain water, etc., and these other water sources masked the effect of cessation of water flow from the Unit 2 containment sump.
The result of an investigation into the event conducted by the NRC's Office of Inspection and Enforcement indicated that deficiencies in the licensee's manage-ment system directly contributed to the event. The licensee's failure to identify and correct the causes of leakage, to require routine containment inspections, or to establish adequate controls to insure that systems required to remove water from the containment were operable, led directly to the flooding event.
The investigation also showed that the facility was restarted on October 20, 1980, without adequate evaluation of the potential consequences of the event with regard to continued plant operation.
The NRC investigation also concluded that certain plant modifications had not been properly evaluated and that the NRC had not been promptly informed of the flooding incident.
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q Actions Taken to Prevent Recurrence
-Licensee - The licensee has taken the following actions:
(1) installed alarms in the control room indicating increasing containment sump levels; (2) installed alarms in the control room to indicate when either submersible pump in the reactor cavity operates; (3) repaired the service water leaks; (4) installed guide bushings on the containment sump pump control floats to prevent their binding; and (5) repaired the containment sump water level indicators. The licensee also plans to replace the containment fan unit cooling coils prior to return to power from the current refueling outage.
Further actions are also being evaluated in response to the NRC letters described below.
NRC - On October 22, 1980, the NRC Region I office issued an immediate action i
letter to the licensee confirming the licensee's commitments to specific actions to prevent recurrence prior to restart of the plant.
The NRC staff determined that the event demonstrated a serious weakness in the licensee's management control system. As a result, on December 11, 1980, the staff proposed imposition of civil penalties in the amount of $210,000 for i
violations, associated with the event, including failure to promptly report the event (Ref. 2).
The NRC also identified four potential unreviewed safety questions associated with the event.
The licensee responded by letters dated January 5 and February 11, 1981.
The licensee contested some aspects of the proposed penalty and the conclusion on serious weakness in the management control system.
The licensee also responded to the potential unreviewed safety questions.
After review of the licensee's response, the staff concluded that there was no basis for mitigation of the civil penalties. Accordingly, on March 2, 1981, 6
an Order imposing Civil Penalties in the amount of $210,000 was sent to the i
licensee (Ref. 3).
Further responses in regard to corrective actions were also.
requested from the licensee.
The licensee's response to the potential unreviewed safety questions is still under review and will be the subject of separate NRC correspondence.
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l IE Information Notice 80-37 was issued on October 24,1980 (Ref. 4) to all holders of operating licenses and construction permits to provide them with i
the details of this' occurrence. On November 21, 1980, IE Bulletin No. 80-24 (Ref. 5) was issued directing all licensees at operating plants to take specific l
short-term actions and to report information to the NRC.
Licensees with plant designs similar-to Indian Point Unit 2 were directed to verify or provide specific equipment and procedural controls to preclude events similar to that which occurred at Indian Point Unit 2.
NRC will evaluate the reports submitted j
by all licensees to determine what other generic longer-term actions may be l
requited.
Further reports will be made as appropriate.
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