ML20210L163
| ML20210L163 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 08/04/1999 |
| From: | VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | |
| Shared Package | |
| ML20210L157 | List: |
| References | |
| NUDOCS 9908090049 | |
| Download: ML20210L163 (13) | |
Text
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.. 10-30-98 REACTOR COOLANT SYSTEM ISOLATED LOOP STARTUP - DRAINED SURVEILLANCE REQUIREMENTS s .ou e n,o* . .. - o , %
4.4.1.6.1 The isolated loop shall be verified drained within 2 hc= pr;or :o cp;.":q 1; 1:sp .;;,
>;&- r~ ud:F": .g S: ;;cp ft - $; RCS- "$ * * < * ' ' " o * *' ' a d -
4.4.1.6.2 The pressurizer water volume shall be verified to be 2 450 cubic feet at least once per 15 minutes during filling of the isolated loop.
4.4.1.6.3 The source range neutron flux monitor shall be demonstrated OPERABLE by performance of:
- a. A CHANNEL FUNCTIONAL TEST within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> prior to commencing isolated loop backfill, and
- b. A CHANNEL CHECK at least once per 15 minutes during backfilling of an isolated loop.
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9908090049 990804 PDR ADOCK 05000338 P PDR NORTH ANNA - UNIT 1 3/4 4-Sb Amendment No. 215
1' i ., 10-30-98 3/4.4 REACTOR COOLANT SYSTEM BASES within 20*F of the operating loops. Making the reactor subcritical prior to loop startup prevents any power spike which could result from this cool water induced reactivity transient.
- itially isolated and drained reactor cool may be returned to service by
- [ panially opening the o Coolant System. Prior t y opening the o g the loop in a controlled manner from the Reactor lves, the following measures are required to e no sudden positive reactivity addition or loss of ea vstem i ory occurs: \
L a) The isolated loop is verified to be drained, thus preventing the dilution of Reactor Coolant System boron concentration by liquid present in the loop.
b) Pressurizer level is verified to be greater than or equal to 450 cubic feet to ensure Reactor Coolant System inventory is maintained for decay heat removal.
Pressurizer level is required to be maintained greatec than or equal to 450 cubic feet during the backfill evolution. In addition, the backfill evolution is limited to one isolated loop at a time.
c) A source range neutron flux monitor channel is required to be monitored to detect ,
any unexpected positive reactivity addition due to an inadvertent mismatch between RCS and blended makeup concentration.
After an initially drained loop is filled from the Reactor Coolant System by partially opening the loop stop valves, the loop is no longer considered to be isolated. Thus, the requirements for returning an isolated and filled loop to service are not applicable and the loop stop valves may be fully opened without restriction within two hours of completing the loop backfill evolution. I 1
The initial pressurizer level requirement has been established such that, even if the stop valves are suddenly opened on all three loops with all of them drained, one of them under vacuum I and no makeup available, the Reactor Coolant System water level will not drop below the middle l l of the reactor vessel nozzles. This ensures continued adequate suction conditions for the residual heat removal pumps.
The safety analysis assumes a minimum shutdown margin as an initial condition.
l Violation of the limiting conditions for loop stop valve operation could result in the shutdown margin being. reduced to less.than that. assumed in the safety analysis. In addition, violation of the j limiting conditions could cause a loss of shutdown decay heat removal.
NORTH ANNA - UNIT I B 3/4 4-la Amendment No. 215 f
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, An initially isolated and drained reactor coolant loop may be returned to service by partially opening a loop stop valve and filling the loop in a controlled manner from the Reactor Coolant System. Blended makeup flow from the Boric Acid Storage Tank and Primary Grade Water Storage Tank is periodically sampled during the backfill evolution to ensure its boron concentration meets the minimum refueling water boron concentration requirement established by Technical Specification 3.9.1. Makeup to the RCS solely through auxiliary spray ,
l during the backfill evolution is prohibited to ensure that a sufficient fraction of l l
makeup flow is mixed with coolant in the active RCS volume and flows through the core, where the source range instrumentation is available to provide secondary indication of improperly blended makeup flow. The vacuum-assisted backfill evolution involves initiation of reactor coolant pump seal injection in the isolated and drained loop to allow establishment of a partial vacuum prior to partially opening the loop stop valve. The following measures are required to ensure no sudden positive reactivity addition or loss of reactor coolant inventory occurs during the backfill evolution:
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10-30-98 REACTOR COOLANT SYSTEM ISOLATED LOOP STARTUP - DRAINED SURVEILLANCE REQUIREMENTS s wooe.s e asov. to co
- mos c. .n.
4.4.1.6.1 The isolated loop shall be verified drained within 2 h;;;; p ::: :e ep:.-ir.; :h: : cap 3;cp
'm!"- fr M9f:!!!:g :h: :::p f;;;r. :h: RCS, "E 4*o Fiw SN* *tia 4 4.4.1.6.2 The pressurizer water volume shall be verified to be 2 450 cubic feet at least once per 15 minutes during filling of the isolated loop.
4.4.1.6.3 The source range neutron flux monitor shall be demonstrated OPERABLE by performance of:
- a. A CHANNEL FUNCTIONAL TEST within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> prior to commencing isolated loop backfill, and
- b. A CHANNEL CHECK at least once per 15 minutes during backfilling of an isolated loop.
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NORTH ANNA - UNIT 2 3/4 4-5b Amendment No.196
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..' ' 10-30-98
.i/4.4 kEACTOR COOLANT SYSTEM
' BASES
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l isolated and drained reactor coolant loo - t~ , ice by
- SW partially opening the loop s d fil oop in a controlled manner from the Reactor
@ Coolant System. Prior to' nmg the ves, the following measures are !
required to e sudden positive reactivity addition or loss o oolant System ory occurs: -
a) The isolated loop is verified to be drained, thus preventing the dilution of Reactor 1 Coolant System boron concentration by liquid present in the loop. !
b) Pressurizer level is verified to be greater than or equal to 450 cubic feet to ensure Reactor Coolant System inventory is maintained for decay heat removal.
Pressurizer level is required to be maintained greater than or equal to 450 cubic feet during the backfill evolution. In addition, the backfill evolution is limited to one isolated loop at a time.
c) A source range neutron flux monitor channelis required to be monitored to detect !
any unexpected positive reactivity addition due to an inadvertent mismatch between RCS and blended makeup concentration.
After an initially drained loop is filled from the Reactor Coolant System by partially ;
opening the loop stop valves, the loop is no longer considered to be isolated. Thus, the !
requirements for returning an isolated and filled loop to service are not applicable and the loop stop valves may be fully opened without restriction within two hours of completing the loop backfill evolution.
The initial pressurizer level requirement has been estab)iIhed such that, even if the stop valves are suddenly opened on all three loops with all of them drained, one of them under vacuum and no makeup available, the Reactor Coolant System water level will not drop below the middle of the reactor vessel nozzles. This ensures continued adequate suction conditions for the residual heat removal pumps.
The safety analysis assumes a minimum shutdown margin as an initial condition. j Violation of the limiting conditions for loop stop valve operation could result in the shutdown margin being reduced to less than that assumed in the safety analysis. In addition, violation of the limiting conditions could cause a loss of shutdown decay heat removal.
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NORTH ANNA - UNIT 2 i B 3/4 4-la Amendment No.196 i l
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- REACTOR COOLANT SYSTEM ISOLATED LOOP STARTUP - DRAINED SURVEILLANCE REQUIREMENTS
.4.4.1.6.1 The isolated loop shall be verified drained within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> prior to commencing the backfill operation.
4.4.1.6.2 The pressurizer water volume shall be verified to be 2450 cubic feet at least once per 15 minutes during filling of the isolated loop.
4.4.1.6.3 The source range neutron flux monitor shall be demonstrated OPERABLE by performance of:
- a. A CHANNEL FUNCTIONAL TEST within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> prior to commencing isolated >
loop backfill, and
- b. A CHANNEL CHECK at least once per 15 minutes during backfilling of an j isolated loop. '
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, NORTH ANNA - UNIT 2 3/4 4-5b Amendment No. 496,
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. 'An initially isolated and draincd reactor coolant loop may be returned to service
~ by partially opening a loop stop valve and filling the loop in a controlled manner from the Reactor Coolant System. Blended makeup flow from the Boric Acid Storage Tank and Primary Grade Water Storage Tank is periodically sampled during the backfill evolution to ensure its boron concentration meets the minimum refueling water boron concentration requirement established by Technical Specification 3.9.1. Makaup to the RCS solely through auxiliary spray during the backfill evolution is prohibited to ensure that a sufficient fraction of makeup flow is mixed with coolant in the active RCS volume and flows through the core, where the source range instrumentation is available to provide -
secondary indication of improperly blended makeup flow. The vacuum-assisted backfill evolution involves initiation of reactor coolant pump seal injection in the isolated and drained loop to allow establishment of a partial vacuum prior to partially opening the loop stop valve. The following measures are required to ensure no sudden positive reactivity addition or loss of reactor coolant inventory occurs during the backfill evolution:
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Attachment 3 i Proposed Technical Specifications Changes l
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North Anna Power Station Units 1 and 2 Virginia Electric and Power Company 1
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REACTOR COOLANT SYSTEM JSOLATED LOOP STARTUP - DRAINED SURVEILLANCE REQUIREMENTS 4.4.1.6.1 The isolated loop shall be verified drained within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> prior to commencing the backfill operation. ~
4.4.1.6.2 The pressurizer water volume shall be verified to be 2450 cubic feet at least once per 15 minutes during filling of the isolated loop.
4.4.1.6.3 The source range neutron flux monitor shall be demonstrated OPERABLE by performance of:
- a. A CHANNEL FUNCTIONAL TEST within 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> prior to commencing isolated loop backfill, and
- b. A CHANNEL CHECK at least once per 15 minutes during backfilling of an isolated loop.
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, 4 l NORTH ANNA - UNIT I 3/4 4-5b Amendment No. MS,
3/4.4 REACTOR COOLANT SYSTEM BASES within 20 F of the operating loops. Making the reactor suberitical prior to loop startup prevents any power spike which could result from this cool water induced reactivity transient.
]
An initially isolated and drained reactor coolant loop may be returned to service by partially opening a loop stop valve and filling the loop in a controlled manner from the Reactor Coolant System. Blended makeup flow from the Boric Acid Storage Tank and Primary Grade Water Storage Tank is periodically sampled during the backfill evolution to ensure its boron concentration meets the minimum refueling water boron concentration requirement established by Technical Specification 3.9.1. Makeup to the RCS solely through auxiliary spray during the backfill evolution is prohibited to ensure that a sufficient fraction of makeup flow is mixed with coolant in the active RCS volume and flows through the core, where the source range instrumentation is available to provide secondary indication of improperly blended makeup flow.
The vacuum-assisted backfill evolution involves initiation of reactor coolant pump seal injection in the isolated and drained Joop to allow establishment of a partial vacuum prior to partially l opening the loop stop valve. The following measures are required to ens ure no sudden positive reactivity addition or loss of reactor coolant inventory occurs during the backfill evolution:
a) The isolated loop is verified to be drained, thus preventing the dilution of Reactor Coolant System boron concentration by liquid present in the loop.
b) Pressurizer level is verified to be greater than or equal to 450 cubic feet to ensure Reactor Coolant System inventory is maintained for decay heat removal.
Pressurizer level is required to be maintained greater than or equal to 450 cubic feet during the backfill evolution. In addition, the backfill evolution is limited to one isolated loop at a time.
c) A source range neutron flux monitor channel is required to be monitored to detect any unexpected positive reactivity addition due to an inadvertent mismatch between RCS and blended makeup concentration.
After an initially drained loop is filled from the Reactor Coolant System by partially opening the loop stop valves, the loop is no longer considered to be isolated. Thus, the requirements for returning an isolated and filled loop to service are not applicable and the loop stop valves may be fully opened without restriction within two hours of completing the loop backfill evolution.
The initial pressurizer level requirement has been established such that, even if the stop valves are suddenly opened on all three loops with all of them drained, one of them under vacuum and no makeup available, the Reactor Coolant System water level will not drop below the middle of the reactor vessel nozzles. This ensures continued adequate suction conditions for the residual heat removal pumps.
The safety analysis assumes a minimum shutdown margin as an initial condition.
Violation of the limiting conditions for loop stop valve operation could result in the shutdown margin being reduced to less than that assumed in the safety analysis. In addition, violation of the limiting conditions could cause a loss of shutdown decay heat removal.
NORTH ANNA-UNIT 1 B 3/4 4-la Amendment No. 3H,
3/4.4 REACTOR COOLANT SYSTEM BASES An initially isolated and drained reactor coolant loop may be returned to service by partially opening a loop stop valve and filling the loop in a controlled manner from the Reactor Coolant System. Blended makeup flow from the Boric Acid Storage Tank and Primary Grade Water Storage Tank is periodically sampled during the backfill evolution to ensure its boron concentration meets the minimum refueling water boron concentration requirement established by Technical Specification 3.9.1. Male ip to the RCS solely through auxiliary spray during the backfill evolution is prohibited to . (re that a sufficient fraction of makeup flow is mixed with coolant in the active RCS volume w ', flows through the core, where the source range l instrumentation is available to provide secondary indication of improperly blended makeup flow.
The vacuum-assisted backfill evolution involves initiation of reactor coolant pump seal injection in the isolated and drained loop to allow establishment of a partial vacuum prior to panially opening the loop stop valve. The following measures are required to ensure no sudden positive reactivity addition or loss of reactor coolant inventory occurs during the backfill evolution:
a) The isolated loop is verified to be drained, thus preventing the dilution of Reactor Coolant System boron concentration by liquid present in the loop. l b) Pressurizer level is verified to be greater than or equal to 450 cubic feet to ensure i Reactor Coolant System inventory is maintained for decay heat removal.
Pressurizer level is required to be maintained greater than or equal to 450 cubic feet during the backfill evolution. In addition, the backfill evolution is limited to one isolated loop at a time.
c) A source range neutron flux monitor channel is required to be monitored to detect I any unexpected positive reactivity addition due to an inadvertent mismatch between RCS and blended makeup concentration.
After an initially drained loop is filled from the Reactor Coolant System by partially l opening the loop stop valves, the loop is no longer considered to be isolated. Thus, the requirements for returning an isolated and filled loop to service are not applicable and the loop stop valves may be fully opened without restriction within two hours of completing the loop backfill evolution.
The initial pressurizer level requirement has been established such that, even if the stop valves are suddenly opened on all three loops with all of them drained, one of them under vacuum and no makeup available, the Reactor Coolant System water level will not drop below the middle of the reactor vessel nozzles. This ensures continued adequate suction conditions for the residual heat removal pumps.
The safety analysis assumes a minimum shutdown margin as an initial condition.
l Violation of the limiting conditions for loop stop valve operation could result in the shutdown l margin being reduced to less than that assumed in the safety analysis. In addition, violation of the limiting conditions could cause a loss of shutdown decay heat removal.
NORTH ANNA - UNIT 2 B 3/4 4-1a Amendment No. M6,
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Attachment 4 Significant Hazards Consideration Determination l
North Anna Power Station Units 1 and 2 Virginia Electric and Power Company i
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. SIGNIFICANT HAZARDS CONSIDERATION DETERMINATION Virginia Electric and Power Company has reviewed the requirements of 10 CFR 50.92 ;
as they relate to the proposed changes for the North Anna Units 1 and 2 and l
determined that a significant hazards consideration is not involved. These changes modify the Bases for Technical Specifications 3/4.4.1 to acknowledge that RCP seal injection is initiated into the isolated and drained loop as a prerequisite for the vacuum-assisted back-fill technique. Since establishment of a partial vacuum in the isolated and
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drained loop may require longer than two hours, changes also relaxes thefdrained-loop ;
verification time from two hours to four before backfilling operations in" Surveillance Requirement 4.4.1.6.1 The following is provided to support this conclusion. '
- 1. Does the change involve a significant increase in the probability or consequences of an accident previously evaluated.
Administrative procedures ensure that the initiation of seal injection in order to establish a partial vacuum in an isolated and drained loop will not create the l potential for an inadverterit and undetected introduction of under-borated water into an isolated loop prior to returning the isolated loop to service. Additionally, extension of the drained loop verification time from two hours to four hours prior to backfill operations will not significantly diminish confidence that the isolated and drained loop will, in fact, be drained at the time the back-fill evolution is initiated. Therefore, there is no measurable increase in the probability or ,
consequences of any accident previously evaluated. I
- 2. Does the change create the possibility of a new or different kind of accident from l any accident previously evaluated.
There are no modifications to the plant as a result of the changes. No new accident or event initiators are created by the initiation of seal injection in order to establish a partial vacuum in an isolated and drained loop, and by the extension of the drained loop verification time requirement from two hours to four hours prior to backfill operations. Therefore, the proposed changes do not create the possibility of any accident or malfunction of a different type previously evaluated.
- 3. Does the change involve a significant reduction in the margin of safety.
The proposed changes have no effect on the safety analyses assumptions.
Changes acknowledge the establishment of seal injection for the Reactor Coolant Pump in the isolated and drained loop as a prerequisite for the vacuum-assisted back-fill technique and extends the drained-loop verification time from two hours to four hours prior to backfill operations. The two hour interval was established to ensure that the drained loop is verified to be drained at a point in time sufficiently close to the initiation of the back-fill evolution such that no intervening event could occur that would render the loop no longer drained.
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.. Relaxation of the drained loop verification time from two hours to four hours will not significantly diminish confidence that the isolated and drained loop will be drainel at the time ths back-fill evolution is initiated. Therefore, the proposed d sngen do not result in a reduction in a margin of safety.
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