Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
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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January 30, 1990
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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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