ML20213D441
| ML20213D441 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 12/19/1980 |
| From: | Rubenstein L Office of Nuclear Reactor Regulation |
| To: | Tedesco R Office of Nuclear Reactor Regulation |
| References | |
| CON-WNP-0321, CON-WNP-321 NUDOCS 8101100054 | |
| Download: ML20213D441 (3) | |
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MUCRAMbUM FOR:
R. Tedecco, Assistant Director for Licensing DL FROM:
L. Rubanstein Assistant Director for Core and Contain-ment Systems, DSI SU3JELT:
REQUEST FOR ADDITIONAL INFORMATION RE: WPPSS-2 SRV DISCHAP.GE LOAD Plant Nam 6: Washington Public Power Supply System Nuclear" Project No. 2 Licensing Stage: OL Docket No.: 50-397 Responsible Branch: LB #1 Project Manager:
D. Lynch Requested Completion Date: N/S Review Status: Aw&& ting Infomation The enclosed. Request for Additional Infomation regarding the Washington Public Potter Supply System (WPPSS) Nuclear Project No. 2 has been prepared by Brookhaven National Laboratory, the staff consultant, after having re-
, viewed the appropriate sections of a report entitled, "SRV Loads - Improved Cefinition and Application Methodology for Mark II Containments " prepared by Burns & Roe, Inc., for application to kPPSS-2. It should be noted that the Project Manager was previously requested to have the SEB and MEB reytew the applicant's metnodology (memorandum from F. Eltawila to W. Butler dated September 18, 1980) presented in the above mentioned report. The results of this review remains pending. It should also be noted that the WPPIS-2 appli-cant has indicated that a plant unique approach to the Condensation Oscilla-tion load spe:f fication is required for WPPSS4 and will be presented to the staff in a meeting scheduled on January 21, 1981.
Original eigned by.
L. S. Rubenstein Lester S. Rubenstein, Assistant Director for Core and Containment Systems Division of Systems Integration
Enclosure:
As stated _
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Containment Systems Branch Request for Additional Information Re: WPPSS SRV discharge load, improved definition and application method
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021.SRV 1.
The Caorso test results exhibit some high frequency pressure spikes in the boundary pressure measurements during the initial period of air clearing transient which are not observed in previous German quencher test data. This suggests that the specific quencher design may be important in determining the characteristics of air clearing loads.
We therefore require a detailed descrip-tion of the quencher geometry, used in WNP-2 (including the hub design) and a comparison with the device tested in Caorso discussing any differences that may exist and how these might influence air clearing loads.
021.SRV 2.
The Caorso test results indicate that the size of the vacuum breaker on the SRV line is important in determining the reflood transient after valve clo-sure and consequently the subsequent valve actuation loads. Are the size, numb-er and characteristics of the vacuum breakers installed on the SRV lines of WNP-2 similar to those of the Caorso plant? If there are differences, what effect on SRV loads is expected and how will it be incorporated in the load definition?
021.SRV 3.
The design values for WNP-2 are based on single valve subsequent actua-tion data from Caorso in-plant tests.
These design values are then used in multiple valve actuation load cases based on a postulation that multiple valve actuation cases involve only first actuation of SRV's. Can this postulation be supported by plant transient analysis of the worst plant transient event expec-ted in WNP-2?
If this is not the case, then we require that the multiple valve effect on pool boundary loads be considered in'the derivation of design values.
It is observed from the Caorso test results that pressure loads from multiple-valve actuations are greater than those from single-valve actuations under simi-lar first actuation conditions.
021.SRV 4.
Figure 6.8 of the WPPSS report shows that the frequency spectrum of the design pressure time histories can bound that of the 90%-90% confidence values and the envelope of the single valve subsequent actuation pressure traces from i
the Caorso tests.
We require that similar comparisons be provided for leaky valve (LV) first actuation data and for multiple valve actuation (MVA) data be-cause of the distinct difference in characteristics in LV data and greater num-l ber of initial pressure spikes in MVA data.
021.SRV 5.
Most of the Caorso subsequent actuation tests were conducted with one of the two vacuum breakers blocked and these data are used in the WNP-2 report to derive the design values. However, the maximum pool boundary pressure mea-sured in the Caorso tests is from a subsequent actuation test with both vacuum breakers operating (Test 22A02), which we believe to be prototypical for Mark II plants.
The maximum value of the peak positive pressure is 8.7 psi and the mean l
value is 5.9 psi for subsequent actuation tests with one vacuum breaker. They i
are 9.4 psi and 7.3 psi, respectively, for those with two vacuum breakers. This t
represents a potential non-conservatism in the data base used in the derivation of design values. We therefore require that this be discussed and considered in the data evaluation and design value derivation.
021.S RV 6.
Ir. order to take into account the differences between WNP-2 design con-ditions and the Caorso test conditions, a pressure amplitude multiplier, based on DFFR correlation, is used to obtain the WNP-2 design values. This procedure Enclosure
. involves the extrapolation of measured pressure amplitudes in Caorso with re-spect to some parameter values, such as SRV steam flow rate, to WNP-2 design conditions using the trends established in the DFFR. Can the trends used in this calculation be supported by available Caorso data?
021.SRV 7.
The proposed vertical pressure distribution in the WNP-2 report is con-stant between the bottom of the suppression pool and the quencher elevation and then decreases linearly to zero at the pool surface. This was arrived at by re-viewing the maximum pressures measured at different elevations. However, as shown in Figure 3.8a in the report, this proposed pressure distribution cannot bound the maximum measured values for all Caorso tests. Furthermore, the use of maximum measured values in the comparison cannot reveal the effect of bubble vertical motion on the pressure distribution. The bubble vertical motion will result in a worse pressure distribution in the later part of the transient. The cross-correlation coefficient of pressure traces measured at different eleva-tions is less than one (about 0.9).
This indicates that there may be some bubble motion effect on the pressure distribution which should be accounted for.
We therefore require that this proposed distribution be modified to assure con-servatism in the design load specification.
021.SRV 8.
In the WNP-2 report, both circumferential and vertical pressure dis-tributions are discussed. What is the method used for calculating the radial pressure distribution? Is it assumed that pressure is constant in the racial d.irection from pedestal to containment walls? If not, what method is used and how is it supported by the measured pressure distribution from the Caorso tests?
021.SRV 9.
For the WNP-2 circumferential pressure distribution the 'DFFR method ks empl oyed. Are the line of sight and SRSS assumptions used in the calculation?
How are these assumptions supported by the Caorso test results? To what extent are these assumptions affecting the WNP-2 load cases? We also require that re-presentative figures be provided showing the pressure distributions on the base-mat, pedestal wall and containment wall for the various SRV discharge cases con-sidered in WNP-2 plant design assessment.
021.SRV 10. What are the two valves selected for the two-valve discharge case? Are the two quenchers selected in the inner or the outer circle? What is the basis for the selection?
021.SRV 11. In the WNP-2 analyses, the pool water is assumed to be incompressible.
The only justification for this assumption is that the cross-correlation coefficients between pressure time histories measured at different locations are high. We don't feel this is sufficient justification because the relationship between thr cross-correlation coefficient and time phase shift and consequently the effect of compressibility on pressure measurements has not been established.
The incompressible flow assumption is subsequently used in the analyses addres-sing FSI effect and in the WNP-2 structural analyses. This assumption is there-fore important and warrants more detailed discussion. Even though the incom-pressible flow assumption can be justified for the Caorso plant, it is still questionable whether it holds true for WNP-2 because the fluid-structure coup-ling effect is expected to be more significant in WNP-2 plant which has a steel containment as opposed to Caorso's concrete containment.
It is further noted that the velocity of sound in water is much reduced by the presence of air and l
steam bubbles in the water.
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