ML20207D054
| ML20207D054 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 12/19/1986 |
| From: | Gridley R TENNESSEE VALLEY AUTHORITY |
| To: | Youngblood B Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8612300309 | |
| Download: ML20207D054 (8) | |
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.y TENNESSEE VALLEY AUTHORITY CHATTANOOGA. TENNESSEE 37401 5N 157B Lookout Place DEC 191986 Director of Nuclear Reactor Regulation L
Attention:
Mr. B. Youngblood, Project Director PWR Project Directorate No. 4 Division of Pressurized Water Reactors (PWR)
Licensing A U.S. Nuclear Regulatory Commission Washington D.C.
20555
Dear Mr. Youngblood:
3 In the Matter of
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Docket Nos. 50-327 Tennessee Valley Authority
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50-328 SEQUOYAH NUCLEAR PLANT - CONTAINMENT' SPRAY DELAY - ADDITIONAL INFORMATION To provide margin in the electrical calculations for sequencing safeguard loads to the diesel generator (D/G), the start time of the containment spray l
(CS) pump is changed from 30 seconds to 180 seconds. On October 14, 1986 NRC's Electrical Branch reviewers requested supplemental information to document the effect on the spray pump delay on the Final Safety Analysis Report (FSAR) analysis of the postaccident containment pressure transient.
The basis for delaying containment spray is as follows.
' The diesel frequency and voltage could not be calculated to be within Regulatory Guide 1.9 limits with random loads combined with the CS pump load.
l At 180 seconda, the D/G has sustained a turbogenerator power boost and loading the CS pump is conservative. Also, one major process load was interlocked out j
until after safeguards loads are energized.
The containment peak pressure and temperature analyses were examined to determine if this change would invalidate the analyses currently presented in i
the FSAR. -The peak containment pressure is the result of a large break l
loss-of-coolant accident (LOCA). Figure 1 (FSAR, figure 6.2.1-20) shows containment pressure relative to time for a large break LOCA. The important parameters for evaluating the acceptability of this change are what energy l
removal role the sprays have before ice bed moltout and the time of containment spray switchover from the refueling water storage tank (RWST) to the containment sump relative to the time of ice bed meltout. Because Sequoyah is an ice condenser plant, the sprays have little effect on tho t
l analysis while ice remains. The sprays do not actively remova energy from the l-containment atmosphere until the ice has melted. Figure 2 (FSAR figure 6.2.1-21) shows a plot of upper compartment tenoperature versus time. This figure shows when the sprays are turned on the upper compartment actually increases in temperature from the initial value of 80 degrees F to the RWST a
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[ ' Director of Nuclear Reactor Regulation DEC 191986 temperature of 105 degrees F.
This temperature remains constant until the sprays are shut down to switch over to the containment sump. The containment temperature drops sharply because the cold air exiting the ice condenser is no longer being warmed by the spray water. The temperature recovers and stabilizes at the outlet temperature of the spray heat exchangers at about 2,600 seconds once the spray pumps have been restarted in the recirculation mode. After ice bed moltout, the temperature of the upper compartment rises because of the hot steam fram the lower compartment finally reaching the upper compartment.
If the sprays had been actively removing energy from the upper compartment, the temperature would have increased rather then' decreased when the sprays.were shut off during the switchover to the emergency sump.
In the FSAR, Chapter 6.2.1 LOCA analysis, the current time of switchover being completed is 2,516 seconds. The time of ice bed moltout is 3,000 seconds.
Changing the diesel loading sequence would change the time of switchover by 150 seconds to 2,666 seconds. This change still leaves a substantial margin before ice bed moltout.
Thus, the current FSAR analysis would not be affected by the change and is still valid.
The mainsteam line break results in the peak containment temperature.
For 4
these events, the ice bed does not melt out before all mass and energy releases from the broken steam line to the containment are terminated. Thus, the change in the containment spray pump loading sequence has no effect on the analysis.
5 The FSAR containment analysis (section 15.5.3) for fission product removal only considers iodine. The removal process for all other fission products is considered to occur by radioactive decay. The analysis only takes credit for iodine removal by the ice condenser and will not be affected by the delay in CS pump start.
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The current FSAR containment analyses support the change in the D/G loading i
sequence. These analyses show the proposed change is not detrimental to the health and safety of the public.
, is a Westinghouse Electric Corporation evaluation in support of 1
containment spray pump delay.
l, If you have any questions, call M. J. Burzynski at 615/870-6172.
Very truly yours, l'
TENNESSEE VALLEY AUTHORITY
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- ridley, rector Nuclear Saf y and Licensing
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Enclosures cc:
See page 3 i
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. Director of Nuclear Reactor Rogulation DEC 19 t3B6 cc (Enclosures):
U.S. Nuclear Regulatory Commission Region II Attn:
Dr. J. Nelson Grace, Regional Administrator 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 Mr. Carl Stahle Sequoyah Project Manager U.S. Nuclear Regulatory Commission 7920 Norfolk Avenue Bethesda, Maryland 20814 Mr. G. G. Zech Director, TVA Projects U.S. Nuclear Regulatory Commission
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Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323
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PimewpPsmerW41$2360358 November 26, 1986 W. R. C. Weir NS-OPLS-OPL-I 86-349 Acting Otier Nuclear Engineer Tennessee Valley Authority 400 West Summit Hill Drive Enoxville, TN 37902 TENNESSE VALLEY AUTHORITY SEQUOYAH UNITS 1 & 2 SEQUOYAH CONTAINMENT SPRAY DELAY ANALYSIS IVA BASI 5 PUR = "I DQCUMENT REVIEW Dear Mr. Weir
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Delaying the Start Time for Containment Spray telecopied to 11-24-66 and im concur with its content and conclusion.
Cttached for reference.
A copy of the above mentioned doctanent is If you have any canments or questions, please contact the undersigned.
V3ry truly yours, WESTI.T, HOUSE ELECTRIC CORPORATION n >
t QHr I M' ^-^ "O h [j[4 M L. L. Williams, Manager ES5D Projects Mid South Area L. V. Ternasic/ der cc: R. C. Weir D. H. Lafever V. A. Bianco R. DeVault R. Bryan R. U. Pathieson I. R. W1111a:tson e
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F*8e 2 cf 3 Basis f or Delaying the Start Time f or Containment Spray I t TVA is planning to change the loading sequence of the containment spray pumps on the emergency diesel generators. The containment peak pressure and temperature analyses were examined to determine if this change would invalidate the analyses currently presented in the FSAR. The delay time in the FSAR analysis assumed for loading the spray pumps on the diesels is 30 seconds. The proposed change would be to make this delay time 180 seconds. The peak containment pressure is the result of a large break LOCA.
The' important parameters f or evaluating the acceptability of this changs ar'e what energy removal role the sprays have beforg ice bed. moltout and the time of containment spray switchover from the RWST to 'the containment sump relative to the time of ice bed moltout. Because Sequoyah is an ice condenser plant the sprays have little effect on the analysis while ice remains. The sprays do not actively remove energy from'the. containment atmosphere untti the ice has mel ted.
Figure 1 (FSAR Figure 6.2.1-21) shows a plot of upper compartment temperature versus time. This figure shows when the sprays are turned on the upper compartment actually increases in temperature frem the initial value of 80 F to the RWST temperature of 105 F.
This temperature remains constant until the sprays'are rhut down to swtchover to the
.. containment, sump. The containment temperature drops sharply b'acause the cold air exi cing the ice condenser is no longer being warmed by the spray water. The temperature recovers and stabi,11res at the cutlet temperature of the spray heat exchangers at about 2600 seconds once the spray pumps have been restarted.
,After 1,ce bed meltout the temperature of the upper compartment
'Pisef due tc the hot steam f rom the lower compartment finally reaching the upper compartment. If the sprays had been actively i
removing energy from the upper compartment the temperature would have increased rather than decr. eased when the sprays were shut l
off during the switchover to the emergency sump. In the FSAR l
Chapter 6.2.1 LOCA analysis the current time of switchover being completed is 2516 seconds. The time of i ce bed mettout is 3000 seconds. Changing the diesel Icading sequence would change the time of switchover by 150 seconds to 2666 seconds. This change still leaves a substantial margin bef ore ice bad moltout. Thus the current FSAR analysis would not be affected by the change and is still valid.
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The main steam line breat results in the peak containmunt temperature. For those events t'se ice bad does nct moltcut oefers all maus 3nd enorgy -elaases fram the brQKen steam line to the c o n t e i n.9 e n t are terminat00. Thue the CnanQe
.n no containment spray pump loading soquence nas no o+fect on the analysis.
The ci.tr r e n t FSAR centainment analysau e.upports the chango in the diesel generator loading G e t1 u e n c e. Th e.".1c an a l y s es sh ow the proposed enange in n=t detrimental t n t h r! health and cafety of the public.
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