ML20064G240
| ML20064G240 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 12/04/1978 |
| From: | Gilleland J TENNESSEE VALLEY AUTHORITY |
| To: | Varga S Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7812080091 | |
| Download: ML20064G240 (4) | |
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830 Power Building CEC 4 19?S Director of Nuclear Reactor Regulation-I.
Attention:
Mr. S. A. Varga, Chief Light Water Reactors 3 ranch No. 4 Division of Project Management U.S. Nuclear Regulatory Commission i
Washington, DC 20555 1
Dear Mr. Varga:
In the Matter of the Application of )
Eocket Nos. 50-327 Tennessee Valley Authority
)
50-328 Enclosed is TVA's revised response to Question 2 transmitted by your letter to G. Williams, Jr. dated May 10, 1977. This question was originally responded to as Question 6.50 in Amendment 52 of the Sequoyah Nuclear Plant Final Safety Analysis Report (FSAR).
Also enclosed is an additional response to your letter of August 11, 1978, and Question 24 transmitted to us in R. S. Boyd's letter dated June 28, 1978. This response is in addition to that transmitted to you in our letter dated November 14, 1978.
1 Both enclosures-vill be incorporated into the next: amend:ent to the Sequoyah Nuclear Plant.FSAR.
Very truly yours, f
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/jJ. E. Gilleland Assistant Manager of Power i
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ENCLOSURE (QUESTION 2 IN 5/10/77 LETTER)
Question 6.50 Describe preoperational tests to be performed with the UHI system to demonstrate that:
Fvdraulic resistance in the UHI system are consistent with those used a.
in the LOCA analyses.
b.
No nitrogen entraining vortices are obtained during active UHI injection.
c.
The level se points on the UHI accumulator is consistent with the UHI injectiun quantities used in the LOCA analyses.
d.
The isolation valves on the UHI lines will function as expected.
Provide details of the tests to be performed and the acceptance criteria for evaluating the results as required by Regulatory Guide 1.68.
Response
The UMI system will be tested in accordance with Regulatory Guides 1.68 and 1.70 For a description of the test, its objectives, and acceptance criterion refer to Table 14.1-2.
The testinc is desizned to evaluate and adjust level settoints on the UHI accumulaters and to adjust operatien of the hydraulic isolatica valves so that the proper amount of unter is injected into the primary system consistant with the LOCA analyses. Samples will be taken during testing to verify that nitrogen concentrations are within acceptable limits.
ENCLOSURE 2 (Additional Response to Au2ust 11, 1978, Letter and question 24 of June 23, 1978, Letter) valves is initiated only in the cvont that actuation signals are generated by the safeguards protection Jogic
("3" signal), two of four RW3T icw level protection locic signals, and two cut of four surp high level signals.
It has been determined that the RiiR pumps continue to receive adequate suction flow during this automatic changcover; thus there is no possibility of pump damage due to loss of suction.
Alarms on RNST low level and level indications frcm both the sump and RW3T are used by the operator to appraise the accident situation and complete the remainder of switchover sequence.
Tabic 6.3-3 describes the sequence of changcover operation from injection to recirculation.
The switchover initiatien point and minimum assured final volume in the RWST befote completion of switchever arc selected en the basis of maximi:Ing the allcwable operator action time for accorpanying manual operations and total water infected to the RC3 uhile avoiding the potential problems due to lc.. levels in either the active sump inside contain=cnt (arca A, Figure 6.3-15)
Revision or in the RWST.
Prior to power operation, crane wall penetrations inside containment wi,11 be scaled as necessary betwcon elevations 679.73 and 693 to retain more water in the active sump, thereby maximizing the active sur.p water level at the onset of the recirculation switchover.
Area C, Figurc 6.3-15, cannot flood until area A is filled to elevation 693 feet.
An analysis of the doubic ended cold leg break indicates that during the switchover from injection to recirculation mode, at the time suction is first taken from the ECCS sump, the depth of water in the active sump will be 13.2 feet (flooded to elevation 693 fect). This depth will be present even if it is postulated that the volume below the reactor vessel (area B, Figure 6.3-15) floods before any water enters the active sump (for example, if i
l the break is at the reactor vessel no::le).
Assumpticas used in this analysis include:
technical specification minimum volumes in the PJ:3T and in the Util and SIS accummula tors ; technical specification minimum ice guss; suitchover sequence as described in Table 6.3-Ja; ice melt as shown in Figurc 6.2-3c; and maximum expected heldup of containment spray water in the upper compartment (arca D, Figure 6.3,,15).
Reactor coolant inventory was not considered on this analysis.
The sequence (as delineated in Tabic G.3-3) is folicwed regardless of which power supply is available (offsite or i
emergency ensite).
The time required to complete the sequence is essentially the l
tire requircu for cperator to perform the ac panying manual cpe ra tion s.
Controls for Erergency Core Ccol: tg Sys:cr i
ccrpenents arc grouped together en the main c ntrol board.
The component position lights verify when the function of a given l
switch has been completed.
6.3-13a
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l ANALYSIS AEPORT REACTOR BUILDING ELEVATION ECCS ACTIVE SUVP' A"J3 INACTIVE SUMP i
LO CA TIONS FIGURE 6.315 7
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