ML20086R431

Proposed Tech Spec Tables 3.3-2 Re Reactor Trip Sys Instrumentation Response Times & 3.3-5 Re ESF Response Times

ML20086R431
Person / Time
Site:	North Anna
Issue date:	12/20/1991
From:	VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
Shared Package
ML20086R430	List: ML20086R429 ML20086R431
References
NUDOCS 9201020052
Download: ML20086R431 (9)

Text

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Attachment 2 Proposed Technical Specification Change North Anna Unit 1 Virginia Electric and Power Company 9:01o2000 9112:a FDR ADOp.: 07090333 e peg i

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TABLE 3.3 R REACTOR TRIP SYSTEM INSTRUMENTATION RFSPONSE TIMES EUNCTIONAL UNIT RES. ONSE TIMES ,

1. Manual Reactor Trip NOT APPUCABW

2. Power Range, Neutron Flux 5 0.5 seconds * ,

3. . Power Range, Noutron Flux NOT APPUCABW High Positive Rate 4, Power Range, Neutron Flux s 0.5 seconds

• High nogalive Rate

5. Interrnodlato Range, Noutron Flux NOT APPUCABW

6. Source Range, Neutron Flux s 0.5 seconds *

7. Overtemperature AT 5.75 seconds' l

8. Overpower AT NOT APPUCABW

9. Pressurizer Pressure - Low s 2.0 seconds

10. Pressurizer Pressure - High s 2.0 seconds

11. Pressurizer Water Level - High $ 2.0 seconds t 1

Neutron detectors are exempt from response time testing. Rosponse of the neutron flux signal portion of the channel time shall be measured from the detector output or input of the first electronic component in the channel.

NORTH ANNA-UNIT 1 3/4 3 10 Amendment NoA S, -84, -14 2, 442,

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d

, TABLE 3.3 5 (Continued)

EtGNEERED SAFETY FEATURES RESPONSE TIMES INITIATING SIGt1AL AND FUNCTION RESPONSE TIMEIN SECONQS

3. ) 1surifer Pressure - LadW a Safety injection (ECCS) s 27.0'/13.0

b. Reactor Trip (from SI) s 3.0

c. Feedwater Isolation s 8.0 d Containment bolation - Phase "A" s 18.0#

o. Auxiliary Foodwater Pumps s 60.0

f. Essential Service Water System Not Applicable ,

4. Differential Pressure Between Steam Lines - Hioh a Safety injection (ECCS) s 13.0#/23.0# A

b. Reactor Trip (from SI) s 3.0

c. Feodwater Isolation s 8.0

d. Containment Isolation - Phaso "A" s 18.0#/28##

e. Auxiliary Foodwater Pumps s 60.0

f. Esser.tlal Service Water System Not Applicab!o

5. Steam Flow in Two Steam Lines - Hlah Coincident gjth Tavo - Low;1ow

a. Safety injection (ECCS) s 16.75#/26.75##

l b. Reactor Trip (from SI) s 6.75 ,

c. Feedwater isolation s 11.75 d Containment isolation - Phase "A* s 21,75#/31.75##

o. Auxiliary Feodwater Pumps s 61.75

f. Essential Servico Water System Not Appucable

g. Steam Line Isolation s 11,75 NORTH ANNA- UNIT 1 3/4 3 28 Amendment NoA6,

Attachment 3 Proposed Technical Specification Change North Anna Unit 2 Virginia Electric and Power Company

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l TABLE 3.3 2 l REACTOR TRIP SYSTEM INSTRUMENTATION RESPONSE TIMES l l

FUNCTIONAL UNIT RESPONSETIMES ,

1. Manual Reactor Trip NOT APPUCABW 1 1

2. Power Range, Neutron Flux s 0.5 seconds *

3. Power Range, Neutron Flux NOT APPUCABE .

i High Positivo Rate 4 .- Power Rango, Neutron Flux s 0.5 seconds

• i High negativo Rato i

5. Intermediate Rango, Neutron Flux NOT APPUCABE -

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6. Source Rango, Neutron Flux s 0.5 seconds * {

7 . Overtemperaturo AT 5.75 seconds' l

8. Ov0rpower AT- NOT APPUCABW 9.- Pressurizer Pressure - Low s 2.0 seconds

10. Pressurizer Pressure - High s 2.0 seconds ,

11. Pressurizer Water Level - High s 2.0 socends ,

Neutron detectors are exempt from response time testing. Response of the noutron flux signal portion of the channel time shall be measures from the detector output or input of the first electronic component in the channel.

NORTH ANNA-UNIT 2 3/4 3 10 Amendment No.-71. -100, -146, e +-~-wr- w o- y M . yes.ms w -, w6mwr - e a,v-+, -,-ere-mn.- *-=-w.

4 TABLE 3.3 5 iContinued)

ENGINEERED SAFETY FEATURES RESPONSE TIMES INITIATING SIGNAL AND FUNCTION RESPONSE TIME IN SECONDS

4. Differential Pressure Between Steam Lines - Higtt

a. Safety injection (ECCS) s 13.0(2)/23.0(3)

b. Reactor Trip (from SI) 53.0

c. Feedwater ! solation 58.0 d Containment Isolation - Phase *A* s 18.0(2)/28.0(3)

e. Auxiliary Feedwater Pumps s 60.0

f. Essendal Service Water System Not Applicable

5. Steam Flow in Two Steam Lines - Hiah Coincident with Tavo - Low. Low

a. Safety injection (ECCS) s 16.75(2)/26.75(3)

b. Reactor Trip (from SI) s 6.75

c. Feedwater Isolation s 11.75

d. .. Containment Isolation - Phase *A" s 21.75(2)/31.75(3)

e. Auxillary Feedwater Pumps s 61.75

f. Essentiat Service Water System Not Applicable

g. Steam Line isolation s 11.75

6. Steam Flow in Two Steam Lines - Hiah Coincident with Steam Line Pressure - Low

a. Safety injection (ECCS) s 13.0(2)/23.0(3)

6. Reactor Trip (from SI) c 3.0

. c. Feedwater Isolation s 8.0 d Containment Isolation - Phase "A"- s 18.0(2)/28.0(3)

e. Auxiliary Feodwater Pumps s 60.0

f. Essential Service Water System Not Applicable

g. Steam Line Isolation s 8.0 NORTH ANNA- UNIT 2 3/4 3 30 Amendment No.

o 1

Attachment 4 i

10 CFR 50.92, No Significant Hazards Consideration North Anna Units 1 and 2 Virginia Electric and Power Company i

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10 CFR 50.92 NO SIGNIFICAtJT. HAZARDS CONSIDfnAllOR Virginia Electric and Power Company proposes to reviso the Technical Specifications for its North Anna Power Station, Units 1 and 2, by increasing the responso timo associated with Reactor Coolant System (RCS) temperaturo measutomont. The specification chango would be implemented after a modification to tho temperaturo measutoment system.

The mod.fication will increase the total response timo measured in accordanco with it's surveillance requirements because the sensor thermal response time in the redesigned system will increase. However, the accident analysis results of UFSAR Chapter 15 will not change. This is due to the fact that the increase in thormal responso timo is offset by a reduction in transport and thermal volay t'me associated with the sensor bypass piping, which is being eliminated. The bypass piping transport and thermal delay, which is of the order of two seconds, is reflected in the curront safety analysis but is not part of the raactor trip or engineered safety feature system response time defined and measured in accordance with the Technical Specifications.

Post. modification testing will be performed to demonstrate that the total channel response time remains within that assumed in the safety analysis. The increase in  ;

response timo listed in the Technical Specifications reflects the fact that a larger portion of the total responso time will be directly measured than with the current system.

Two specifications are involved. Specification 3.3.1.1 lists the maximum timo 10 automatically trip the reactor when the power, computed from the temperature, exceeds the limit. Specification 3.3.2.1 lists the maximum timo to automatically start certain enginoored safety features when two out of three steam lines havo excessivo flow and the average reactor coolant temperaturo is below its low low" limit. All of these response times would be increased by 1.75 seconds by the proposed changes.

The North Anna reactors each have three coolant inlets (cold logs) and thrca coolant outlets (hot legs). The temperature is measured at each leg in order to compute the average temperature and the difference between hot and cold legs.

Temperature is measured using electrical devices called Resistance Temperature Detectors (RTDs). The current system uses RTDs that are directly immersed in reactor coolant. In order to permit replacing RTDs without draining the RCS, separate piping systems or bypass loops with isolation valves aro used. Radioactive particulates tend to accumulate in these bypass loops, increasing radiation exposure for prsorir 31 working near the steam generators or RCS pumps. The isolation valves sometimes leak causing a forced outage, j The modification will eliminate the RTD bypass loops and substitute thermowells that extend into the RCS piping. A thermowell is a well with an RTD, extending into the pipe. The RTD will not be immersed in the coolant and it can be replaced without I draining the system. Shortening the coolant flow path to the RTD reduces the response time by 1.75 seconds. Since the RTD is not directly immersed in reactor coolant, the heat must diffuse through the thermowell. This increases responso time l

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i by 1.75 seconds. The net effect will be the same overall response time. The benefits  !

are a radiation exposure reduction of 4800 man rom, due to olimination of the bypass piping, and a reduced forced outage rate, due to the elimination of potentially leaky 4

valves.

Virginia Electric and Power Company has reviewed the proposed Technical Specification change against the critoria of 10 CFR 50.92 and has concludod that the proposed change does not pt.se a significant hazards consideration. This determination was based on the following points:

1. Accident Probability or Consequence Increase. The proposed chango will not change the RCS temperature or temperature related setpoints. Total response timo for temperature related setpoints, including the coolant thormal lag, will be unchanged. The probability and cor..sequenco of thermowell failure or leakage is bounded by the analysis for the current system. The probability of loakage is reduced due to the elimination of 240 feet of piping and associated valves.

2. Accident Probability Croation. The proposed change will not create the possibility of a now or diffarent kind of accident. The protection and control systems will not be signt $ntly changes. A thermowell failure is similar to a bypacs loop f ailure.

3. Safety Margin Reduction The safety margin depends on the temperaturo setpoints and the total delay inherent in the temperature monitoring system.

Because these are not being changed, the safety margin reduction is not reduced.

Based on the above evaluation, Virginia Electric and Power Company concludes that the proposed chango satisiles the no significant hazards consideration standards of 10 CFR 50.92(c) and, accordingly, a no significant hazards consideration finding is justified.

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