ML19260C482
| ML19260C482 | |
| Person / Time | |
|---|---|
| Issue date: | 07/17/1979 |
| From: | Charemagne Grimes Office of Nuclear Reactor Regulation |
| To: | Hanauer S Office of Nuclear Reactor Regulation |
| References | |
| REF-GTECI-A-07, REF-GTECI-CO, TASK-A-07, TASK-A-7, TASK-OR NUDOCS 8001030673 | |
| Download: ML19260C482 (3) | |
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JUL 171979 Generic Task A-7 MEMORANDUM FOR:
S. Hanauer, Director, Unresolved Safety Issues Program FROM:
C. Grimes, A-7 Task Manager
SUBJECT:
BR00XHAVEN TRIP REPORT On July 12-13, 1979, I met with our consultants at the Brookhaven National Laboratory to summarize the review of the Mark I Long Term Program proposed load definition techniques.
During the course of these discussions we covered (1) the individuals who will be res-ponsible for developing draft evaluations and acceptance criteria for specific loads; (2) GE's responses to our first-round request for additional information; (3) the draft questions for our second-round request for additional information; and (4) those areas where additional information is needed before we can conclude on a specific load de-finition procedure or develop alternate acceptance criteria.
The following issues were identified as the significant issues that must be overcome before our evaluation can be completed.
Uncertainty in Condensation Oscillation Loads An unexpected result of the Full Scale Test Facility (FSTF) data was that condensation oscillation loads (i.e., high steam flux with low air content) are more significant than the chugging loads (i.e., low steam flux with low air content).
The load definition for this regime has been derived from a short period of highest loading during one FSTF test run (M8).
From the data we currently have (i.e., FSTF, 4T, Marviken and GKM II), it appears that this one FSTF test run is 2
the only data that exists in this regime (i.e., 60-80 lb/sec ft and less than 1% air content).
Although we acknowledge that the tested condition is conservative, since this loading condition is not stochastic, this test only represents one data point.
Therefore, we cannot conclude on the uncertainty or confidence in the condensation oscillation load specification. We immediately notified GE of this finding, ahd requested that they search for any additional data in this regime, that we may not have, which could be used to establish the uncertainty of the load magnitudes.
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JUL 17 1979 I also noted that our consultants are skeptical that GE can develop a sufficient argument to preclude an asynrnetric condensation oscillation loading condition, based on observed phase relationships. Since these are substantial loads, this will become a significant issue.
Froth Impingement loads GE's response to our request for additional information concerning the definition of froth impingement loads was totally inadequate. As a result, we are developing an alternate criteria which will undoubtedly increase the load magnitude and expand its range of application.
Asymmetric Vent Flow The containment pressure response is calculated assuming complete mixing of the blowdown mass and energy with the containment atmosphere.
However, in the event of a localized small break within the drywell, a preferential flow of steam into a few vents could be maintained by condensation in that section of the vent system and suppression pool.
Air flow through the remainder of the vent system could cause an asym-metric heatup of the pool. Preliminary calculations performed by BNL, indicate that the suppression chamber design pressure and temperature could be exceeded approximately five minutes after a small-break, assuming no safety-relief valve discharge or RHR operation, if steam flows into less than 65% of the pool.
I personally judge that this case is too conservative. However, we have not yet been able to define a case with a lesser amount of conservatism.
Pool Swell Vent Flow Distribution In our first-round request for additional information, we asked the Owner's Group to justify the sizing of downcomer orifices in the EPRI 3-D test facility.
Several orifice sizes were used to establish a vent system flow distribution, and the sizing of these orifices must be justified to support (1) the proposed pool swell asimuthal and longitudinal pressure distributions on the torus; (2) the proposed pool surface longitudinal velocity variation; and (3) the proposed vent leader impact timing, which are derived from the EPRI tests.
To respond to our request, EPRI contracted Professor Chambre' (UC - Berkeley) to perform analyses with a t'wo-dimensional, compressible flow model, which could be used to relate scaled test conditions with full-scale equivalent flow distributions.
Preliminary results from Professor Chambre's model indicate that, although the flow distributions are roughly the same, an 1700 213
a JUL 171979
_3-acoustic wave is eliminated in the tested condition which could cause a perturbation in the full-scale bubble pressure and, thus, a change in the loading condition. GE is presently reviewing the implications of this finding. However, additional analyses being perfonned by Professor Chambre' and GE will not be completed for another two months.
We believe that acceptance criteria can be specified at this time, exclusive of the results of the ongoing analyses.
However, we have arranged to review the results of the preliminary analysis with the Owners Group in a meeting planned for July 24, 1979, to assure that our acceptance criteria will cover any uncertainties raised by thest analyses.
The majority of draft evaluations and acceptance criteria for individual load definition techniques are expected to be completed by July 24, 1979.
We plan to review these draft criteria with the Owners Group's representa-tives at that time, to identify any significant areas of disagreement.
C. Grimes Plant Systems Branch Division of Operating Reactors cc:
D. Eisenhut E. Adensam M. Aycock C. Anderson B. Grimes T. M. Su L. Shao K. Wichman G. Lainas J. Fair V. Noonan W. Butler 1700 214