United States Nuclear Regulatory Commission - Protecting People and the Environment

Confirmatory Requirements Relating to Condensation Oscillation Loads for the Mark I Containment Long Term Program (Generic Letter 79-48)


GL79048 

                               UNITED STATES 
                       NUCLEAR REGULATORY COMMISSION 
                          WASHINGTON, D. C. 20555 

                             October 2, 1979 

ALL BOILING WATER REACTOR LICENSEES (Except: Dresden 1, Humboldt Bay, Big 
Rock and LaCrosse) 

SUBJECT:  CONFIRMATORY REQUIREMENTS RELATING TO CONDENSATION OSCILLATION 
          LOADS FOR THE MARK I CONTAINMENT LONG TERM PROGRAM 

On August 15, 1979, the staff met with representatives of the Mark I Owners 
Group to discuss the acceptance criteria being developed by the staff to 
begin implementation of the Mark I Long Term Program (LTP). One of the 
staff's criteria requires confirmatory condensation tests in the Full-Scale 
Test Facility (FSTF). The Mark I Owners Group representatives stated that 
they consider additional FSTF tests unnecessary. 

As a result of our review of the proposed load definition procedures for the
design basis accident "condensation oscillation" loads (i.e., high vent flow
rate with low air content), we have concluded that there are insufficient 
data to establish a reasonable measure of the uncertainty in the load 
magnitudes for this regime. Although we believe that the condensation 
oscillation loads proposed in the Mark I Containment Program Load Definition
Report (LDR), NEDO-21888, are sufficiently conservative with respect to the 
results of FSTF test run M8, we have not found sufficient applicable data to
give an adequate estimate of the uncertainty in the load magnitude so 
defined, such that we can assure that the uncertainty is smaller than the 
conservatism in the load definition technique. In making this assessment, we
have considered the use of the other full-scale data sources and small-scale
phenomenological studies. The questions that have been raised regarding the 
applicability of these data to this issue have not been resolved and will 
not be resolved in the near future. 

We believe that the LDR condensation oscillation load specifications, as 
modified by the staff's acceptance criteria, form a sufficient basis to 
proceed with implementation of the LTP, since FSTF test M8 is prototypical 
for Mark I and the load definition technique has conservatively assessed 
that test data. Consequently, we intend to issue the acceptance criteria to 
unit initiate the LTP plant-unique analyses. We will require in these 
criteria that the conservatism in the condensation oscillation loads be 
confirmed by performing a sufficient number of additional large break, 
liquid blowdown tests in FSTF to establish the uncertainty in the load 
magnitudes. 

In addition, the staff has recently raised concerns relating to the 
phenomena associated with downcomer condensation oscillation loads. These 
concerns evolved from insufficient downcomer-vent header response data. The 
additional FSTF test should provide improved instrumentation for the 
downcomer-vent header system, particularly for the "tied" downcomers. 

                                                                 7911200331 
.

                                  - 2 -

We will require that each licensee commit, on behalf of the Mark I Owners 
Group as a whole, to perform these tests and provide the associated test and
plan schedule by October 31, 1979. 

                                        Sincerely, 


                                        D. G. Eisenhut, Acting Director 
                                        Division of Operating Reactors 
.

Mr. William J. Cahill, Jr.                                           50-3 
Consolidated Edison Company of New York, Inc.                        50-247

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     Executive Vice President 
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     Consolidated Edison Company 
          of New York, Inc. 
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     Edward J. Sack, Esquire 
     Law Department 
     Consolidated Edison Company 
          of New York, Inc. 
     4 Irving Place 
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     Natural Resources Defense Council 
     917 15th Street, N.W. 
     Washington, D. C. 20005 

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     Apartment 51 
     Kendal at Longwood 
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     Theodore A. Rebelowski 
     U. S. Nuclear Regulatory Commission 
     P. O. Box 38 
     Buchanan, New York 10511 

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