ML20128N657

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Comments on Draft Vols IV-VI of BMI-2104,presented at Peer Review 840126 & 27 Meetings.Comments Concern Completed Calculations for Sequoyah Ice Condenser Plant,Recalculated Surry Results & Completed Calculations for Zion Plant
ML20128N657
Person / Time
Site: Sequoyah, Surry, Zion, 05000000
Issue date: 02/22/1984
From: Vogel R
ELECTRIC POWER RESEARCH INSTITUTE
To: Silberberg M
NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES)
Shared Package
ML20127B155 List:
References
FOIA-285-110, FOIA-85-110 NUDOCS 8507130136
Download: ML20128N657 (3)
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k February 22, 1984 l

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Dr. Melvin Silberberg Accident Source Term Program Office Office Nuclear Regulatory Research 7915 Eastern Avenue Mail 1130 SS

,l Silver Springs, MD 20910 i

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Dear Dr. Silberberg:

1 This letter formalizes EPRI's comments on the draft sections g

(Vol. IV,. V, and. VI) of Report BMI-2104, presented at the peer i review meeting on January 26 and 27, 1984. These comments pertain to (1) the completed calculations for the Sequoyah i

ice condenser plant, (2) the recalculated Surry results, and (3) the completed calculations for the Zion plant.

I j I would like to compliment you for the conduct of the meetingt l .

. in general, it was very informative. There was, however, one j presentation that was not at all clear due to inadequate time -

the CUES'" report by Sandia. Since we feel that this work is o

important, we would very much like some sort of an opportunity to review it so that we might intelligently commant on it.

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8 I would also like to compliment the NRC contractors on attempt-ing ' to indicate the water location in a reactor accident.

While progres.s has been made in this area, one suspects that more work remains to be done. As you know, the presence of water has a major effect on the behavior of fission products in an accident. Therefore, any study should track the water, per-haps to the kilogram level of mass balance. A case in point is the Surry V-sequence analysis done by EPRI. It now appears that -

even the most unfavorable location for a break in the RER line occurs in a place where the pipe will be submerged in three-feet of water. Pool scrubbing should result, appreciably reducing the fission product release to the environment. We

.' would, therefore, encourage you to once again examine the BMI analyses with regard to the disposition of water, and adjust it in those instances where it is inadequate.

' 8507130136 850425 PDR FOIA ALVARE285-110 PDR l 3412.Hiereos, Avenue. Post office 80s 10412, Paio Alto, CA 94303 leisonone hts 886 2000 .

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Letter to IQ-Dr. Melvin Silberberg BMI-2104

, February 22, 1984

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. The hydrogen burn model estployed in BMI-2104 differs considerably from the phanr==n= observed in large-scale experiments, parti-cularly when the containment safety features are active. The  !

calculational model predicts pressures above the 60 psia assumed i

failure level while the ===4== incremental ' pressure spike',

observed in 17 Nevada tests, each lasting 20 minutes, was about 4

5 paia. We believe that estimates of hydrogen combustion pres-

, sures in BMI-2104 are unrealistic. Similarly, experiments have ,

shown that pre-mixed enviremments of 8 vol 4 hydrogen and 40 vol 4 i

, of steam burned vigorously, even in an initially quiescent atmos-

! phare. Thua steam inerting of the lower compartment may not occur

specially when combustion sources will be present following vessel j failure and fuel dispersal, as in the postulated TMLB' scenario.

Presence of steam also substantially reduces the ragnitude of the pressure rise.

l The magnitude of hydrogen generation in the MARCE analysis is very likely too high due to the assumptions made both for the heat-up phase of the intact core, and the phase in which the core

. slumps in the lower plenum. The calculated early con *=4 a=ent i

-Q failure in the TMLB' - y-sequence depends upon the total hydrogen calculated in the .HRCE code.

, As we all appreciate,the retention of fission products in the

. Primary coolant system (PCS) is a function of the temperatures in the systaat and the gas flow patterns and rates. The BMI-2104 calculations have asstaned once-through flow patterns and estimate l l a two orders of magnitude increase in the flow rate when the core l

i slumps in the lower plantan, which sweeps. the fission products.

inter the cooler regions of the PCs. The gas flow rate is a

! function of.the particle size assumed for the interaction of. the molten core with the water in the lower plenum and may not be l correct.- Also, the flow patterns in the vessel during the core -

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heat-up and slump phases may not be as assumed in the MARCE code l calculations. All of the above considerations significantly i affect the estimates of the fission product retention in the primary system. We feel that this part of the study may need j further consideration. These problems are, unfortunately, dif-ficult.

i One technical area of particular concern to all of us is the question of revolatilization/resuspension of aerosols deposited in the primary coolant system. The technical case on this issue is weak. Since. it is not clear whether a potential exists for -

substantial changes in the results, we suggest that a task force  ;

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?A Letter to

.%' Dr. Melvin Silberberg i

i BMI-2104

!  ! February 22, 1984 i Page 3 be established to follow the unfolding of this problem as the

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several groups involved (both experimental and analytical) do their work. Input will be required on the recirculation thermal l

i hydraulics, radiation energy distribution, chemistry, and surface interacions involved.

I 1 In summary, we unfortunately believe that another review of some i kind is required before EPRI feels comfortable that a firm tech-nical basis for the BMI-2104 report exist. This review should cover the QUEST program and.the revolatilization issue.

-EPRI appreciates the opportunity to comment on this study. '

i We recognize.the large effort to date and encourage you to ~

I continue your efforts. '

Sincerely urs, R. C. Voge O Senior Scientific Advisor

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l cc John Taylor - -

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Walt Loewenstein Frank Rahn Raj Sehgal l

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