Information Notice No. 90-07: New Information Regarding Insulation Material Performance and Debris Blockage of PWR Containment Sumps

                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                    OFFICE OF NUCLEAR REACTOR REGULATION
                           WASHINGTON, D.C.  20555

                              January 30, 1990


Information Notice No. 90-07:  NEW INFORMATION REGARDING INSULATION 
                                   MATERIAL PERFORMANCE AND DEBRIS 
                                   BLOCKAGE OF PWR CONTAINMENT SUMPS


Addressees:  

All holders of operating licenses or construction permits for nuclear power 
reactors.

Purpose:  

This information notice is intended to alert addressees to new information 
concerning performance of insulating materials in 
post-loss-of-coolant-accident (LOCA) environments within pressurized water 
reactor (PWR) containment sumps when such materials become debris which may 
block the sump.  It is expected that recipients will review the information 
for applicability to their facilities and consider actions, as appropriate, 
to avoid similar problems.  However, suggestions contained in this 
information notice do not constitute NRC requirements; therefore, no 
specific action or written response is required.

Description of Circumstances: 

By letter (Attachment 1) dated October 19, 1989, the NRC staff was informed 
by Performance Contracting, Inc. of the results of recently conducted tests 
on Owens-Corning NUKON fiberglass insulating material.  The tests were 
conducted by Performance Contracting, Inc. at the request of a European 
customer in order to further investigate the potential for containment sump 
blockage due to insulating material debris in the "long-term" following a 
LOCA.  "Long-term" was defined as one day to 30 days duration following LOCA 
initiation.  Similar tests were previously conducted by the Swedish Nuclear 
Power Inspectorate on NUKON and M.I.T. insulating materials.  The results 
obtained were comparable to those discussed in the attached letter.

The NRC staff previously considered containment sump performance including 
debris blockage concerns under Unresolved Safety Issue (USI) A-43.  USI A-43 
was resolved in 1985 with the issuance of several NUREGs and Revision 1 to 
Regulatory Guide 1.82.  However, no specific actions were required by 
licensees.  The NRC staff focus was on the short-term effects of containment 
sump blockage assuming chemically neutral cooling water at room temperature.

Performance Contracting, Inc. reported that the recent tests were conducted 
on NUKON insulation material with water at a temperature of 180 F and pH of 
9.1 for a 7-day period.  The results indicated that head loss across the 
insulation 



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material increases significantly after about 24 hours due to a reduction in 
flow area caused by compaction of the fiberglass material at elevated pH 
conditions.  On the basis of discussions with Owens-Corning, this is 
consistent with what would be anticipated, because devitrification of 
fiberglass occurs under alkaline conditions.  

Assuming that full cooling water (residual heat removal) flow is necessary 
to ensure adequate post-LOCA heat removal capacity for 24 hours and beyond 
after accident initiation, the effect of the increased pressure loss and 
associated flow reduction, caused by compaction of insulation material 
debris, may have an effect on the post-LOCA cooling performance.  Additional 
tests conducted with water at the same temperature, but with a chemically 
neutral pH as is the case in boiling water reactor (BWR) plants, did not 
result in an increase in head loss.  Thus, the phenomenon observed during 
these tests appears to be relevant to plants with alkaline sump conditions.

Discussion:

Because some plants may potentially have alkaline post-LOCA sump conditions, 
addressees are being made aware of this new information regarding the 
potential for increased containment sump blockage caused by compaction of 
fiberglass insulation debris under high pH conditions so that they may 
assess the impact on their plant-specific licensing basis post-LOCA sump 
performance and reactor cooling analyses.  Performance Contracting, Inc. 
indicated that a test report of the newly performed tests is available for 
use by interested licensees.

This information notice requires no specific action or written response.  If 
you have any questions about the information in this notice, please contact 
one of the technical contacts listed below or the appropriate NRR project 
manager.




                              Charles E. Rossi, Director
                              Division of Operational Events Assessment
                              Office of Nuclear Reactor Regulation

Technical Contacts:  J. Wermiel, NRR
                     (301) 492-0870

                     F. Witt, NRR
                     (301) 492-0823

Attachments:
1.  Letter from Gordon H. Hart (Performance Contracting, Inc.)
      to Dr. Thomas E. Murley (NRC) dated October 19, 1989
2.  List of Recently Issued NRC Information Notices

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