ML17156B482
| ML17156B482 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 11/20/1989 |
| From: | Cintula T NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| To: | |
| Shared Package | |
| ML17156B481 | List: |
| References | |
| TASK-AE, TASK-T923 AEOD-T923, NUDOCS 8911280164 | |
| Download: ML17156B482 (2) | |
Text
AEOD TECHNICAL REVIEW REPORT*
UNIT:
DOCKET NO.:
LICENSEE:
NSSS/AE:
Susquehanna-2
-388 Pennsylvania Power Im Light Co.
General Electric/Bechtel TR REPORT HO.:
AEOD/T923 DATE:
November 20, 1989 EVALUATOR/CONTACT:
T. Cintula
SUBJECT:
DELAMINATING FOIL IHSULATION IN PRIMARY CONTAINMENT
SUMMARY
Large quantities of loose aluminum foil were found throughout the drywell during the start of a refueling outage.
The aluminum foil resulted from extensive delamination of insulation used in the drywell.
As the NRC has long been concerned with potential sources of debris generation in containment, and because the generic issue was resolved in 1986, the data bases were surveyed to see if similar problems might still be ongoing in the nuclear industry.
The data searches did not find any additional recent events, so it would appear that the insulation delamination was an isolated occurrence and further industry action would not be appropriate at this time.
DISCUSSION On March 5, 1988, a walkdown of primary containment following commencement of a refueling outage at Susquehanna Steam Electric Station Unit 2 (SSES-2) found large quantities of loose aluminum foil throughout the drywell.
The licensee concluded that loose aluminum foil could become debris during the blowdown phase of a loss of coolant accident and could block ECCS pump suction strainers, resulting in inadequate NPSH, causing pump damage.
The aluminum foil was from surface delamination of fibrous insulation blankets made by Alpha Associates, Inc.
The aluminum foil fiberglass cloth insulation had been used extensively on valve bodies, pipe hangers and other areas difficult to insulate in the SSES-2 drywell.
The exact method of delamination could not be determined, but could be the result of extended exposure to operating temperatures, humidity, radiation or some combination of these and other factors.
Although the rated service temperature of the insulation was 500 degrees Fahrenheit normal operating temperatures in the drywell do not exceed 135 degrees Fahrenheit.
The insulation does not have a design humidity or radiation rating.
At SSES-2, it was estimated that 5,000 square feet of this insulation was used in more than 300 locations within the drywell. It was estimated that 50 percent of the insulation had undergone some degradation.
Based on the apparent extensive breakdown of the aluminum foil laminating adhesive in the SSES-2 drywell, it was expected that continued exposure to operating conditions would have resulted in further delamination.
A different insulation material is used at SSES-l, and no insulation delamina-l tion has been observed at this unit.
- This document supports ongoing AEOD and NRC activities and does not represent the positions or requirements of the responsible NRC program office.
39ii230ib4 35'i120 PDR ADOCK 050003~88' PDC
On March 21, 1988, the foil delamination problem was reported persuant to 10CFR Part 21.
Subsequently, NRC Information Notice No. 88-28:
POTENTIAL FOR LOSS OF POST-LOCA RECIRCULATION CAPABILITY DUE TO INSULATION DEBRIS was published.
The Information Notice noted that representatives of Alpha Associates, Inc.
have indicated that other companies supply the same or similiar insulation and that its use may be widespread.
A few days later, on March 18, 1988, the licensee for Unit 1 of the Nillstone Nuclear Power Station reported via LER 88-004 a similar concern for potential fouling of their ECCS strainers.
In this case, an engineering evaluation found that the area of the existing strainers was insufficient to pass the debris from fibrous insulation in the drywell.
At Millstone-l, the same insulation as SSES-2 is used without an aluminum foil facing.
The engineering evaluation was conducted to compare the condition of the drywell at Hillstone-1 to the regulatory position noted in Regulatory Guide 1.82 Revision 1, "Water Sources For Long Term Recirculation Cooling Following A Loss-Of-Coolant-Accident."
AEOD CONCERNS There have been many publications addressing potential problems of debris blocking containment emergency sump screens in pressurized water reactor's or residual heat removal pump strainers in boi ling water reactors.
For example, Regulatory Guide 1.82, "Sumps for ECCS E Containment Spray Systems" was published in 1974 and Generic Issue A-43, "Containment Emergency Sump Perfor-mance" was initiated in 1979 and resolved in 1986.
In view of the extent and longevity of containment debris information, it was disconcerting to receive two recent LERs on the subject.
As both LERs reported potential deficiencies with insulation blankets of the same manufacturer, and the manufacturer's surmission that their insulation or similar insulation may have widespread useage in the nuclear
- industry, AEOD thought that searches for other instances of recent potential insulation breakdown would be appropriate.
FINDINGS AND CONCLUSIONS The available search
- systems, the Sequence Coding and Search System (SCSS),
the Nuclear Plant Reliability Data System (NPRDS) and the Nuclear Document Control System (NUDOCS) were used to find if any other recent events of insulation deficiencies in primary containment have been reported.
None of the searches revealed any additional ongoing insulation deficiencies in primary containment.
Therefore, it would appear that these two LERs represent isolated cases rather than an ongoing generic deficiency.