ML20215G053
| ML20215G053 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 12/17/1986 |
| From: | TENNESSEE VALLEY AUTHORITY |
| To: | |
| Shared Package | |
| ML20215G049 | List: |
| References | |
| NUDOCS 8612240235 | |
| Download: ML20215G053 (15) | |
Text
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ENCLOSURE 1 PROPOSED TECHNICAL SPECIFICATION CHANGE SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2
\\
DOCKET NOS. 50-327. -328 (TVA SQN TS 76)
INCREASE IN LOADING SEQUENCE DELAY FOR CONTAINMENT SPRAY PUMPS LIST OF AFFECTED PAGES Unit 1 3/4 3-31 Unit 2 3/4 3-31 i
8612240235 861217 PDR ADOCK 05000327 P
TABLE 3.3-5 (Continued)
ENGINEERED SAFETY FEATURES RESPONSE TIMES INITIATING SIGNAL AND FUNCTION RESPONSE TIME IN SECONDS 6.
Steam Flow in Two Steam Lines-High Coincident with Steam Line Pressure-Low a.
Safety Injection (ECCS) i 13.0(7)/23.0(1) b.
Reactor Trip (from SI)
< 3.0 c.
Feedwater Isolation
< 8.0(2) d.
Containment Isolation-Phase "A"(3) 18.0(8)/28.0(9) e.
Containment Ventilation Isolation Not Applicable f.
Auxiliary Feedwater Pumps
< 60 g.
Essential Raw Cooling Water System h65.0(8)/75.0(9) h.
Steam Line Isolation
< 8.0 i.
Emergency Gas Treatment System
[38.0(9) 7.
Containment Pressure--High-High
- 8 a.
< M-GO(9) b.
Containment Isolation-Phase "B" 65(8)/75(9) c.
Steam Line Isolation i 7. 0 d.
Containment Air Return Fan
> 540.0 and i 660 R16 8.
Steam Generator Water Level--High-High a.
Turbine Trip-Reactor Trip i 2. 5 b.
Feedwater Isolation i 11.0(2) 9.
Main Steam Generator Water Level -
Low-low a.
Motor-driven Auxiliary
< 60.0 I4)
Feedwater Pumps b.
Turbine-driven Auxiliary
-< 60.0 Feedwater Pumps (5)
MAR 25 82 SEQUCYAH - UNIT 1 3/4 3-31 Amendment No.
12
TABLE 3.3-5 (Continued)
ENGINEERED SAFETY FEATURES RESPONSE TIMES 1
INITIATING SIGNAL AND FUNCTION RESPONSE TIME IN SECCNDS 6.
Sten -'cw in Lo Sten Li es-Hign Coincicent witn Staam t.ine Pressure-Lew a.
Safety Injection (ECCS) 5 13.0(7)/23.0(1) b.
Reactor Trip (from SI) 1 3.0 c.
Feedwater Isolation
< 8.0(2) d.
Containment Isolation-Phase "A"(3) 18.0(81/28.0(9) e.
Containment Ventilation Isolation Not Applicable f.
Auxiliary Feedwater Pumps 5 60 g.
Essential Raw Cooling Water System 5 65.0(9)/75.0(9) h.
Stea.3 Line Isolation
< 8.0 i.
Emergency Gas Treat..ent System h,38.0C9) 7.
Containment Pressure--High-High g,
a.
Containment Spray 1 &&-6F '
b.
Containment Isolation-Phase "B" 1 65(9)/75(9)
}
c.
Steam Line Isolation i 7.0 d.
Containment Air Return Fan
> 540.0 and i 560 8.
Steam Generator Water level--High-High a.
Turcine Trip-Reactor Trip i 2.5 b.
Feedwater Isolation i 11.0(2) 9.
Main Steam Generater Water level -
Lew-Low a.
Motor-driven Auxiliary
< 60.0 Feeewater Pumps (4) b.
Turcine-driven Auxiliary 1 60.0 Feec ater Pumps ( )
I t
- g SEQUOYAH - UNIT 2 3/4 3-31
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ENCLOSURE 2 PROPOSED TECHNICAL SPECIFICATION CHANGE SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 DOCKET NOS. 50-327 -328 (TVA SQN TS 76)
DESCRIPTION AND JUSTIFICATION FOR PROPOSED INCREASE IN LOADING SEQUENCE DELAY FOR CONTAINMENT SPRAY PUMPS
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. DESCRIPTION OF CHANGE e.
This change will revise Table 3.3-5, Engineered Safety Features Response Times, for the Containment Spray (CS) (item 7.a) response time from 58 seconds to 208 seconds.
REASON FOR CHANGE TVA is performing electrical systems reviews as described in part III, section 4.0, of the Sequoyah Nuclear Performance Plan (NPP), Volume II.
Included in this review was an analysis of the diesel generator (D/G) loading scheme. The analysis identified problems in maintaining D/G frequency and voltage with the present loading scheme.
Random loads were originally assumed to actuate once the D/G has started. As part of the electrical system review. TVA reevaluated the treatment of random loads. The random load block was assumed to occur concurrently with each sequenced load block rather than just occurring at initial diesel loading.
D/G frequency and voltage could not be maintained within Regulatory Guide 1.9 limits with the random loads combined with the CS pump.
The resolution of this problem is accomplished through two changes to the loading scheme.
A review of the random loads has identified two major plant air handling units (AHUs) that do not need to be evaluated as random loads. One of the AHUs is not automatically loaded back on the D/G.
The other AHU is interlocked to prevent a process demand signal from starting the ANU until after the sequenced loads have been energized and the D/G has stabilized at nominal voltage and frequency. This random load clarification alone does not correct the loading scheme to prevent exceeding the D/G load margin of Regulatory Guide 1.9.
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The second change to the loading scheme takes into account the time for D/G power to increase as a result of the turbocharger being run by hot exhaust gases as opposed to the gear drive.
The switchover from the gear drive to the hot exhaust gas drive occurs no later than three minutes after D/G start.
The present CS start time occurs at 30 seconds on the loading scheme. The proposed change will delay this start to 180 seconds, thus moving CS pump start outside the three-minute time period required for the D/G power boost.
In effect, the CS sequencing delay is being increased by 150 seconds, from 30 seconds to 180 seconds. The current technical specification response time of i
58 seconds will be increased by 150 seconds to 208 seconds. The difference in times between the sequencing delay and response time includes time for signal generation, diesel start, and pump and valve response.
Together, the above two changes to the D/G loading scheme will resolve the D/G frequency and voltage problems identified in the electrical systems review.
This technical specification change addresses a change to the CS response time caused by the sequence timer change.
It is not intended to address all actions from the electrical systems review. The remaining actions resulting from the electrical systems review will be addressed in a separate submittal, i
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. JUSTIFICATION FOR CHANGE
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The containment peak pressure and temperature analyses were examined to determine if this change would invalidate the analyses currently presented in the Final Safety Analysis Report (FSAR). The peak containment pressure is the result of a large break 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
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change are what energy removal role the sprays have before 1:e bed moltout and i
the time of containment spray switchover from the refueling water storage tank i
(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 atmor;phere until the ice has melted.
Figure 2 (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 from the initial value of 80 degrees F -to the RWST temperature of 105 degrees F.
This temperature remains constant until the sprays are shut dcwn 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 j
due to the hot steam from 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 than decreased when the sprays were shut off during the switchover to the emergency sump.
In the FSAR, Chapter 6.2.1, Containment Functional Design (LOCA analysis), the current time of switchover being completed is 2,516 seconds. The time of ice bed meltout 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 l
FSAR analysis would not be affected by the change and is still valid.
I The mainsteam line break results in the peak containment temperature.
For j
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 i
analysis.
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 l
iodine removal by the ice condenser and will not be affected by the delay in CS pump star 1.
i the current FSAR containment analyses support the change in the D/G loading sequence. These analyses show the proposed change is not detrimental to the health and safety of the public.
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ENCLOSURE 3 PROPOSED TECHNICAL SPECIFICATION CHANGE SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 DOCKET NOS. 50-327, -328 (TVA SQN TS 76)
WESTINGHOUSE ELECTRIC CORPORATION CONCURRENCE IN SUPPORT OF INCREASING THE LOADING SEQUENCE DELAY FOR CONTAINMENT SPRAY PUMPS 9
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Wealnshouse Water Reactor TVA-65-738 Esctric Corporation Olvisions wow fanmeomi wg Pn0W8h Pennevenis 152WC355 November 26, 1986 NS-OPLS-OPL-I-86-349 Mr. R. C. Weir Acting Q11er Nuclear Engineer Tennessee Valley Authority 1400 West Summit Hill Drive Knoxville, TN 37902 TENNESSEE VALLEY AUTHORITY SEQUOYAH UNITS 1 & 2
_SEQUOYAH C0hiAIhMENT SPRAY DELAY ANALYSIS TVA BA515 FOR DUM DOCUMMI REVEd
Dear Mr. Weir:
Delaying the Start M e for Containment Spray telecopied to concur with its content and conclusion.
11-24-86 and we attached for reference.
A copy of the above mentioned document is If you have any ccenments or questions, please contact the undersigned.
Very truly yours, WESTINGHOUSE ELECTRIC CORPORATION n >
L.
j QHr T W1 - ^2 b / [4 P L. L. Williams, Manager ESSD Projects Hid South Area L. V. Temasic/dmr 1
cc: R. C. Weir D. H. 'stever V. A. P.ian::o A. DeVault R. Bryan R. U. Mathieson I. R. Williamson e
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Basis for Delaying the Start Time for Containment Spray TVA is planning to change the loading sequence of the contatnment ~
spray pumps on the amergency 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 analyst s assumed f or leading the spray pumps on the diesels is 30 seconds. The proposed change would be to make this delay time ISO seconds. The peak. containment pressure is the result of a large creak LOCA.
The'important parameters for evaluating the acceptability of this changs ar~e what energy removal role the sprays have beforg ice bed.moltoutlan.d the time of containment spray switchover from the
+-
RWST to 'the containmer.t 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 f rom' the. containment atmosphere until the ice has melted.
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 from the initial value of 80 F to the RWST temperature of 105 F.
This temperature remains constant until the sprays'are shut down to swtchover to the
.. c on t a.i n y.ent, su.mp. The containment temperature drops snarply because the cold air exiting 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,c_e bed.meltout the temperature of the upper compartment
' fi ses' duw to ' the het steam from 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 than 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 2516 seconds. The time of ice bed meltout is 3000 seconds. Changing the diesel loading sequence would change the time of switchover by 150 seconds to 0666 seconds. This change still leaves a substantial margin before ice bad meltout. Thus the current FSAR analysis would not be affected by the change and is still valid.
The main steam line break results in the peak containment temperature. Fce these events the ice buc does net moltout oefera 1
all mauu ond enorgy "cloasen f rom the bro ren steam line to the centstnment are terminatod. Thuc the change in the containment spray pump loading noquence nas no otfect on the analysts.
The current FSAR contatnment anal ysos qupport: the chango in the diesel generator loading cet1uence. Theoc analyses chow the propcocd change t u not detrimental tn t hr! h ee41 t h and safety of the public.
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ENCLOSURE 4 PROPOSED TECHNICAL SPECIFICATION CHANGE SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 DOCKET NOS. 50-327, ~328 (TVA SQN TS 76)
DETERHINATION OF NO SIGNIFICANT HAZARDS CONSIDERATIONS FOR PROPOSED INCREASE IN LOADING SEQUENCE DELAY FOR CONTAINHENT SPRAY PUMPS e
4
SIGNIFICANT HAZARDS CONSIDERATIONS 1.
Is the probability of an occurrence or the consequences of an accident previously evaluated in the safety analysis report significantly increased?
No.
The containment spray (CS) system is part of the Containment Heat Removal System. The primary design of the Containment Heat Removal Spray Systems is to spray cold water into the containment atmosphere when appropriate in the event of a loss of coolant accident (LOCA) and thereby ensure that containment pressure does not exceed the containment shell design pressure of 12 psig. Temperature and pressure transients shown in the Final Safety Analysis Report (FSAR) for the worst case LOCA remain relatively constant until switchover to sump recirculation. At this point, 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 once the spray pumps have been restarted. The temperature increases further af ter ice bed moltout, but remains within design limits. Substantial margin still exists between the time sump recirculation begins and ice bed meltout occurs.
Delaying actuation of CS to 208 seconds will not have any significant effect on the containment temperatures and pressures as previously evaluated in the FSAR.
2.
Is the possibility for an accident of a new or different type than evaluated previously in the safety analysis report created?
No.
The proposed change makes a minor modification to an accident previously evaluated in the FSAR. The only change being made is the system response time. The evaluation of the proposed delay for CS actuation concludes that system operation and performance will be as presently expected in maintaining containment pressure and temperature design limits.
3.
Is the margin of safety significantly reduced?
l No.
The evaluation of the proposed delay for CS actuation concludes that containment pressure mitigation will remain within the safety limits.
The delay for CS actuation will also delay the time before switchover to l
containment sump recirculation occurs. However, adequate safety margin still exists between recirculation flow actuation and ice depletion.
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