ML20148J121

Responds to 780330 & 780612 NRC Request for Addl Info on Demonstration Test & Forwards 3 Repts on Sump & Spray Pumps

ML20148J121
Person / Time
Site:	Sequoyah
Issue date:	11/07/1978
From:	Gilleland J TENNESSEE VALLEY AUTHORITY
To:	Varga S Office of Nuclear Reactor Regulation
Shared Package
ML20148J126	List: ML20148J121 ML20148J175 ML20148J181 ML20148J188
References
NUDOCS 7811150137
Download: ML20148J121 (2)

Text

{{#Wiki_filter:. ._ ._ . ~- - i 4 LTENNESSEE VALLEY AUTHORITY CH ATTANOOGA TENNESSEE 374o: 830 Power Building November 7, 1978 Director of Nuclear Reactor Regulation '

                                                                                                                      }

Attention: Mr. S. A. Varga, Chief Light Water Reactors Branch No. 4 Division of Project Management U.S. Nucicar' Regulatory Commission Washington, DC 20555

Dear Mr. Varga:

In the)latter of the Application of ) Docket Nos. 50-327 Tennessee Valley Authroity ) 50-328 Your letter of March 30, 1978, to N. B. Hughes defined the NRC staff's concerns about demonstration testing of the Sequoyah scale model containment sump and requested additional information. Our initial response to your request'was. submitted to you in my letter of May 19, 1978. Enclosed is our final report on the scale-model study and two reports which address your additional concerns as defined in the TVA/NRC telephone conversation of June 12, 1978. The three documents are:

1. "Model Study of the Sequoyah RHR Samp," Report No. WM28-1-45-102, l October 1978.

2. "A Study of the. Effects of Steam Jets and Water Jets on the Emergency Sump.at Sequoyah Nuclear Plant Units 1 and 2," September 1978.'

3. " Revised NPSH Calculations for the RHR and Containment Spray Pumps Operating in the Recirculation Mode," October 27, 1978.

As described in the model study, the sump design has been modified to eliminate air entrainment during initial filling and to provide additional conservatism regarding the formation of vortices. The structures associated with the cump have~been designed to withstand the blowdown forces that could result from all postulated pipe breaks. The sump loss' coefficient has been determined from experimental data obtained in the model tests as shown in'the model study.

                  .The water level will be 13.2 feet above the containment floor before transfer from the- injection mode to the recirculation mode.              The Sequoyah

?-

                   . final safety analysis report section 6.3.2.2 has been revised to describe
                  ,chan3cs that have been made to ensure this water level.

1 . . Performance of 'the -sump will not' be impaired by steam ' jets or by air entri.ined by, water. jets from postulated pipe breaks. Also, changes in three' ice condenser drains have been made to eliminate another 1 ( possible_ source of air;entrainment. The study on. steam jets and z water jets de' scribes the examination of' these phenomena and demonstrates. hev are of no significant concern. 04 o -{ 7811 7g/  ; 37 4 4

, An Equal Opportunity Employer k .

                                                                                      ~

f 7 1 4 i Mr. S. A.-Varga- I The NPSH calculations for the RHR and containment spray pumps have been revised from the original calculations, as submitted in my letter to Karl Kniel dated June 26, 1975. The new NPSH calculations include the more realistic water level and water temperature, and include the sump and screen losses determined from the model study. The NPSH available was found to exceed that required by a large margin. The available head is considerably more than twice the required head and, in fact, exceeds the required head by approximately 30 feet for each type pump. l t The calculations of piping losses from the sump to the pumps have been , verified to be conservative by preoperational testing at the plant site. For example, when the RHR pump that is connected to the sump through the piping circuit having the larger loss (circuit ABC in figure 1 of the NPSHstugy)wasoperatedaloneatfullflow, the measured piping loss was 1.5 - 0.5 psi. The piping loss from tha sump to one RHR pump calculated using the techniques in the enclosed NPSH study was found to be 2.25 psi for the piping circuit having the larger loss (ABC in figure 1) and 2.01 psi for the circuit having the smaller loss (WXY in figure 1). Dismantling of the present sump model is scheduled to begin December 4, 1978, in preparation for examination of the performance of the sump design for the Watts Bar Nuclear Plant. You are invited to visit Narrii Engineering Laboratories the month of November to observe a series of confirmatory scale-model tests of the proposed Sequoyah containment sump. Please get in touch with D. L. Lambert at FTS 854-2581 to make arrangements for this visit. Very truly yours, "J. E. Gilleland Assistant Manager of Power i Enclosure (10) f 4 i J}}