United States Nuclear Regulatory Commission - Protecting People and the Environment

Summary of Meetings Held on April 22 & 23, 1980 with Representatives of The Mark I Owners Group (Generic Letter 80-41)


                              UNITED STATES 
                          WASHINGTON, D.C. 20555 
                                MAY 9 1980 

Generic Task No. A-7 

DOCKET NOS.:   50-219, 50-220, 50-237, 50-245, 50-249, 50-254, 50-259, 
               50-260, 50-263, 50-265, 50-271, 50-277, 50-278, 50-293, 
               50-296, 50-298, 50-321, 50-324, 50-325, 50-331, 50-333, 
               50-341, 50-354, 50-355, and 50-366. 

LICENSEES:     Boston Edison Company, Carolina Power & Light Company, 
               Commonwealth Edison Company, Detroit Edison Company, Georgia 
               Power Company, Iowa Electric Light & Power Company, Jersey 
               Central Power & Light Company, Nebraska Public Power 
               Niagara Mohawk Power Corporation, Northeast Nuclear Energy 
               Company, Northern States Power Company, Philadelphia Electric
               Company, Power Authority of the State of New York, Public 
               Service Electric and Gas, Tennessee Valley Authority, Vermont
               Yankee Nuclear Power Corporation. 

FACILITIES:    Oyster Creek Nuclear Generating Station, Nine Mile Point Unit
               No. 1, Pilgrim Unit No. 1, Dresden Units Nos. 2 and 3, 
               Millstone Unit No. 1, Quad Cities Units Nos. 1 and 2, 
               Monticello, Peach Bottom Units Nos. 2 and 3, Browns Ferry 
               Units Nos. 1, 2 and 3, Vermont Yankee, Hatch Units Nos. 1 and
               2, Brunswick Units Nos. 1 and 2, Duane Arnold Energy Center, 
               Cooper, Fitzpatrick, Enrico Fermi Unit No. 2, and Hope Creek 
               Units Nos. 1 and 2. 


On April 22 and 23, 1980, the staff met with representatives of the Mark I 
Owners Group in San Jose, California to discuss confirmatory analysis and 
testing programs relating to the Mark I Containment Long Term Program. The 
specific agenda items (i.e., downcomer "condensation oscillation" loads, 
pool swell compressibility effects analyses, and the supplementary 
full-scale condensation test series) are those ongoing issues for which 
resolution is necessary to complete the generic aspects of the program. The 
purpose of this meeting was to identify the information that would be needed 
to conclude on these issues. The meeting attendees are listed in Enclosures 
1 and 2. 

Tuesday, April 22 

R. Palaniswamy, Bechtel, presented the proposed downcomer load specification
for the "condensation oscillation" regime. A refined analytical model of the
Full Scale Test Facility (FSTF) vent system has been calibrated 

                                  - 2 -

with static ("jack" test) and dynamic ("snap" test) downcomer - vent header 
response data  The analytical model and response data comparisons are 
described in Enclosure 3. 

The load specification was derived by assuming an oscillatory (i.e., 
sinusoidal) pressure load within the vent system and comparing the 
calculated structural response to the response data from FSTF. From the 
analyses, a design load has been derived equivalent to a 1.5 psi static 
differential pressure, + - 2.5 psi at 5.5 Hz* oscillatory vent header 
pressure and + - 5.0 psi at 5.5 Hz* oscillatory downcomer pressure. The load 
would be applied in-phase with a damping value of 6% (lowest damping 
observed in the applicable "snap" tests). Comparisons of the calculated 
response to the proposed design load with the FSTF response data indicates 
that the proposed design load is between 35% and 95% conservative. A report 
to document the bases for this load specification will be completed about 
May 1980. 

The staff considered the approach presented to be viable. However, the 
analyses suggest that the downcomer response mode is near resonance, 
evidenced by significant amplification. Thus the vent system analytical 
model may be responding to a mode of response other than the "wishbone" 
mode. Therefore, the staff indicated that the assumed 6% damping must be 
justified (e.g., compare displacement in the pool) and the range specified 
for the driving frequency must consider the proximity of the response mode 
frequency. These considerations will be addressed in the forthcoming report 
and the load specification will be confirmed by data from the supplement 
FSTF tests. 

R. Torak, Accurex, described the analyses which were used to investigate the
effects of compressibility on scaled pool swell loads (report NEDE-24778-P).
The analyses consisted of a finite element, compressible, one-dimensional 
vent flow model coupled to a semi-empirical bubble/poolswell model. The 
bubble model was calibrated with quarter Scale Test Facility (QSTF) data. 
The coupled analytical model was then applied to ideal QSTF test conditions 
and equivalent full-scale conditions. The results of these analyses indicate 
that compressibility tends to mitigate the pool swell loads by a net 
reduction in the mass and energy into the bubble. For water leg lengths less 
than about four inches, the download or the torus tends to be higher at 
full-scale conditions; however, the Mark I Owners indicated that all plants 
intended to operate with water legs greater than six inches. 

Following the discussion of the compressibility analyses and conclusions, 
the Mark I Owners representatives addressed the comments submitted by our 
consultants at BNL in a letter dated March 12, 1980 (J. D. Ranlet, 

  *  GE will specify a frequent range to assure conservative plant-specific 

                                 - 3 - 

BNL, to C. Grimes, NRC). The principal comment concerned the relative 
accuracy of the analyses with respect to the number of nodes and timestep 
size. R. Torak presented the results of error studies (Enclosure 4) which 
indicate that the total error in load magnitude is less than about 5%, 
compared to a mitigation effect of approximately 20% for the net upload. The
net downloads were affected less by error. The principal reason for the 
relatively low error was the prototypically low Mach numbers for the vent 
flow rate (approximately 0.31.)  Additional information concerning node and 
time-step sensitivity and model descriptions were presented in response to 
questions raised in the BNL report. 

The staff and consultants concluded that two additional analyses (i.e., 
full-scale and equivalent 1/4-scale) should be performed which would model 
the drywell with a constant mass inflow and use the same scaled vent system 
models. The comparison of the integrated mass flow up to the time of peak 
upload for these two analyses would be sufficient to demonstrate the "mass 
defect" between the scaled QSTF and full-scale equivalent vent flow. The 
Mark I Owners Group agreed to provide such analyses in a letter report. The 
staff concluded that this comparison would provide a sufficient basis to 
demonstrate whether compressibility would constitute a mitigating effect for
the Mark I vent flow conditions. 

The Mark I Owners Group inquired about the additional efforts that would be 
needed to take quantitative credit for the mitigating effects of 
compressibility on the torus pool swell loads. The staff responded that 
considerable justification would have to be presented for the assumptions 
and judgements inherent to the vent flow model and extrapolation of the 
empirical bubble formation parameters. The staff indicated that quantitative 
credit would be unlikely, because the analyses would have to be good enough 
to quantify pool swell loads, in which case a three-dimensional flow model 
may be necessary. 

Wednesday, April 23 

C. Collins, GE, described the FSTF supplemental tests that are to be 
performed in May and June 1980 (Enclosure 5). These tests will duplicate 
test M8 (design-basis liquid break) and will be designated M11 and M12. The 
only difference in the facility from the M8 configuration will be that all 
of the downcomer pairs will be "tied" and additional instrumentation has 
been installed on the downcomer-vent header system. The Mark I Owners Group 
indicated that examination of the vent system welds was performed before the
"snap" tests and no evidence of damage due to the previous test series was 

The Mark I Owners Group suggested a meeting with the staff in July 1980 to 
review the "quick-look" data from tests M11 and M12 and data comparisons to 
test M8 The "quick-look" data would include (1) test initial conditions, (2)
bottom-center wall pressure transients, (3) pressure transients from the 
extreme downcomer pairs, and (4) downcomer - vent header and downcomer - tie
strain measurements. The staff requested 

                                 - 4 - 

that, in order to provide an expeditious resolution to that issue, the Mark 
I Owners should plan to submit an interim report following the July 1980 
meeting which would provide sufficient information for the BNL consultants 
to develop a supplement to the Mark I SER. Specifically, this report should 
include comparisons of the pressure - frequency spectra from tests M8, M11, 
and M12 and the Load Definition Report (LDR) to establish the conservatism 
in the torus shell pressure load specification, and a phasing evaluation of 
the pressure transients in the two extreme downcomer pairs. A complete 
report of the test results could then be issued in December 1980, as 
planned, without affecting the overall schedule for the resolution of the 
Mark I program. 

W. Kennedy, Structural Mechanics Associates, described the results of 
analyses which were performed to investigate the effects of the relative 
phasing of the harmonic components of the "condensation oscillation" torus 
shell pressure - frequency spectra (Enclosure 6). The results of this 
analysis indicated that neither the assumed pressure amplitude, 2% damping, 
for steady-state loading contributed much to the conservatism in the design 
load. Cumulative Distribution Functions (CDFs) were developed for the 
Bechtel model of FSTF (i.e., Monticello) and the NUTECH model of Oyster 
Creek. From an assessment of these CDFs, the following design rule was 

     1.   Use LDR pressure - amplitude spectra and 2% damping. 

     2.   Absolute sum the responses of the three (3) highest amplitude 

     3.   Square-root-the-sum-of-the-squares (SRSS) the responses of the 
          remaining 27 harmonics (up to 30 Hz). 

This design rule results in calculated structural responses which 
essentially match the peak responses observed in FSTF test M8. 

The staff noted that the load specification proposed in the LDR was 
considered acceptable because the conservatisms provided by the coupled load
- structure analysis techniques (i.e., absolute sum of all of the hormonics)
would offset the uncertainties associated with the stochastic nature of the 
phenomena (i.e., uncertainty in the load magnitude). Therefore, further 
consideration of the proposed design rule must be deferred until the load 
magnitude uncertainty can be quantified from the supplemental FSTF tests. 

Once adequate documentation of these tasks has been submitted to the NRC, as
described above, and providing there are favorable results from 

                                 - 5 - 

the supplementary FSTF test series, the staff will conclude the generic 
aspects of the Mark I Containment Long Term Program with a supplement to the
Safety Evaluation Report. 

                                        C. I. Grimes 
                                        A-7 Task Manager 
                                        Generic Issues Branch 
                                        Division of Safety Technology 

Enclosure:  As stated 

cc:  See Distribution Sheet 

                               ENCLOSURE 1 

                       MARK I OWNERS GROUP MEETING 

                              APRIL 22, 1980 

Name                               Organization 
C. I. Grimes                       NRC/DOR 
J. R. Fair                         NRC/DOR 
D. B. Fetters                      PECo 
D. F. Lehnert                      Detroit Edison 
J. C. Carter                       TVA 
A. A. Sonin                        BNL/MIT 
J. D. Ranles                       BNL 
R. Kosson                          BNL/Grumman
R. J. Mulford                      GE 
L. D. Steinert                     GE 
G. Wade                            GE 
S. A. Hucik                        GE 
U. C. Saxena                       GE 
A. Mukherjee                       GE 
L. J. Sobon                        NUTECH 
P. D. Hedgecock                    NUTECH 
G. Uram                            NUTECH 
B. Whiteway                        NUTECH 
T. Ballard                         NUTECH 
R. Torak                           Accurex 
W. S. Kennedy                      Accurex 
R. Kendal                          Accurex 
R. Palaniswamy                     Bechtel 
J. J. Bhatt                        Bechtel
S. A. White                        SCSI

                              ENCLOSURE 2 
                       MARK I OWNERS GROUP MEETING 
                              APRIL 23, 1980 

Name                               Organization 

C. I. Grimes                       NRC/DOR 
J. R. Fair                         NRC/DOR 
D. B. Fetters                      PECo 
D. F. Lehnert                      Detroit Edison 
J. D. Ranlet                       BNL 
R. Kosson                          BNL/Grumman 
C. Brennen                         BNL/CIT 
T. J. Mulford                      GE 
R. H. Moen                         GE 
L. D. Steinert                     GE  
S. A . Hucik                       GE
G. Wade                            GE 
U. Saxena                          GE 
C. E. Collins                      GE 
R. L. Mapes                        GE 
J. L. Baskin                       NUTECH 
R. A. Malte                        NUTECH 
T. A. Ballard                      NUTECH 
A. F. Deardorff                    NUTECH 
G. Uram                            NUTECH 
B. Whiteway                        NUTECH 
W. S. Kennedy                      Accurex 
L. M. Broderick                    Wyle 
W. Kennedy                         SMA

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