ML20062D008
| ML20062D008 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 11/08/1978 |
| From: | Utley E CAROLINA POWER & LIGHT CO. |
| To: | Stello V Office of Nuclear Reactor Regulation |
| References | |
| NG-3514(B), NUDOCS 7811160135 | |
| Download: ML20062D008 (5) | |
Text
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g-T), 3 7 Carolina Powee' 5~Ogtit Company l
November 8, 1978 FILE: NG -3514(B)
SERIAL: CD-78-3005 Mr. Victor Stello, Director u
Division of Operating Reactors t
Office of Nuclear Reactor Regulation United States Nuclear Regulatory Commission Washington, D. C.
20555 BRUNSWICK STEAM ELECTRIC PLANT, UNIT NOS. 1 AND 2 DOCKET NOS. 50-325 AND 50-324 LICENSE NOS. DPR-71 AND DPR-62 REQUEST FOR LICENSE AMENDMENT - VACUUM BREAKER OPERABILITY
Dear Mr. Stello:
This letter supplements our request of November 3,1978 (GD-78-2959)
'to amend the Technical Specifteations for a temporary period to modify the oper-ability requirements of the suppression pool-reactor building vacuum breakers.
This letter expedites documentation of information discussed with the staff during the meeting on November 6, 1978, and during telephone conversations on November 7, 1978.
Considering the containment as a pressure vessel, our Architect /Eni;ineer used the 1968 ASME code as guidance in determining the need for a vacuum breaker such that the drywell vacuum would not exceed the drywell design basis of -2 psig.
The sizing of the suppression chamber-to-reactor building vacuum breaker is based on criteria contained in the response to Comment 5.28 in Appendix M of the Brunswick FSAR. Structurally, the containment. was designed in compliance with ACI.
The containment spray system is available for the eperator to reduce
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containment pressure and temperature following a LOCA. The containment is designed to withstand the temperatures and pressures resulting from a LOCA without utilizing containment spray. The system must be manually actuated by operator action. There are two valves in series, each of which is normally v
mentsondrywellpres)sure,LOCAsignal,andreactorvesselwaterlevelareThe closed.
j satisfied.
f Your staff questioned the possibility of inadvertent actuation of the containment spray system and whether the resultant transient would create a situation requiring operation of the vacuum brsakers between suppression pool l
j and reactor building. As discussed with your staff, inadvertent actuation of j
the containment spray cannot occur for the following reasons: The containment t ;
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.2-spray system must be manually actuated by nn operator opening two valves in the system, one of which is keylocked.
Each valve is powered from separate divisions.
i In addition, in order for the valves to be opened, the following interlock require-ments must be met: drywell pressure > 2.5 psig; LOCA signal; and reactor vessel i
water level greater than two-thirds of core height.
i' In evaluating closing of the existing manual valve, we have reviewed possible scenarios in which containment spray might be utilized to determine if the vacuum relief functisn would be required. The two bounding cases reviewed f
were the design basis LOCA and a small steam break. The conclusion of this review is as follows:
-p A.
Design Basis LOCA The containment response to a design basis LOCA is discussed in 9
Section 14.4 of the BSEP FSAR. Figure 14.4-11 shows containment pressure as a function of time, after LOCA, in which the containment spray is initiated approximately 600 seconds after the event. Because of the increased mass inventory in the containment resulting from the LOCA, the pressure decays to a value of 5 to 10 psig when spray and containment temperature equalize. The b,i.
vacuum relief function is not required for this case.
B.
Small Steam Break l
Now, considering a small steam break, we go through this sequence:
After the break occurs, containment pressure increases slowly. With regard to 4
i containment pressure only, a control room operator could initiate containment spray when containment pressure exceeds 2.5 psig (i.e., the water level and l
LOCA signal interlocks must also be satisfied). Once spray is initiated, it will automatically shut off if containment pressure drops to 2.5 psig; this shut-off feature is single-failure proof. However, during closure of the spray vr.lve(s), an additional amount of spray water will be introduced into containment. This will cause containment pressure to drop below 2.5 psig.
No analysis exists to show the minimum pressure experienced in this case.
Therefore, vacuum breaker function should be available in this instance. The proposed action of 3.6.4.2 in the proposed Technical Specifications requires l
Q, that the manual valves be opened prior to initiating containment spray. This assures that vacuum breakers will be available if required.
(If containment spray were not initiated during the entire small steam break scenario, the con-tainment design high pressure limit would not be exceeded.)
ll In the event it was necessary to manually open the butterfly valve I
in the vacuum breaker line, we have analyzed valve accessibility from radiation l:
considerations and valve operability in view of existing AP.
Based on maximum design basis radiation leak rate from the drywell following a LOCA and con-tinuing fer 30 minutes, and assuming an individual was in the ar-a 15 minutes to operate the valve, his dose would be approximately less than 1.5R, which is less than the quarterly exposure limit. The valve is designed to be manually operable following a LOCA. This valve was purchased under the designed speci-fications of other containment isolation valves, and therefore, can withstand design basis accident conditions and remain operable, i
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.Mr. Vict r Stallo.
l The attached Technical Specification revisions supersede those transmitted with our November 3, 1978, letter. The low drywell pressure signal is representative of a potential approach to the condition of concern (negative j
drywell differential pressure).
Increased surveillance upon receipt of such a
- j signal as r: quired by Action 3.6.4.2.a will keep the operators fully cognizant
-i of the drywell conditions and prepared to take immediate action.
If the dry-
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well pressure drops to -0.5 psig, the Action 3.6.4.2.b requires that immediate action be taken to open the manual valves in the suppression pool-reactor building 4
vacuum breaker line, thereby ensuring that adequate vacuum relief is available.
j Action 3.6.4.2.c will provide assurance that the vacuum relief function is available at any time the containment spray system is operated.
It is our desire to maintain the operational flexibility to utilize the containment spray system in accordance with plant administrative procedures. Thus, as we indicated during our November 6 meeting with your staff, we are presently evaluating permanent modifications to the vacuum breaker lines such that an automatically actuated valve would be in the location of the present manually operated butterfly valve. At the present time, we have not finalized engineering and design details, nor are we assured of the equipment availability. This information will be available within two weeks. We are committed to making our
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be,st effort in undertaking this modification so that, as requested by your staff, the modification can be completed within 60 days.
In the event that any design or equipment availability information is determined that would affect our schedule, we will notify your staff immediately.
If you have any questions concerning this submittal, please contact our staff.
Yours very truly, ii f E C Utley l;
Senior Vice President Power Supply i
' T, DLB/mf Attachment Sworn to and subscribed before me this day of November, 1978 4
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g Notary Public My commission Expires:
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l CONTAINMENT SYSTLMS j
SUPPRESSION POOL - REACTOR BUILDING VACUUM BREAKERS i
LIMITING CONDITt0N FOR OPERATION 3
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.rj 3.6.4.2 All suppression pool-Reactor Building vacuum breakers shall be OPERABLE with an opening setpoint. of < 0.5 psid with the manual valves closed. l
,3 APPLICABILITY: CONDITIONS 1, 2 and 3.
ACTION:
- a. With indication of a low drywell pressure alarm, record the drywell pressure
.i every 15 mir.utes.
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- b. With the drywell pressure indicating- -0.5 psis, the manual valves in the suppression pool-reactor building vacuum breaker lines shall be opened.
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- c. The manual valves in the suppression pool-reactor building, vacuum breaker
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lines shall be opened prior to operation of either the drywell or sup-pression pool spray systems.
d.If Actions a, b, or e above cannot be met, be in at least HOT SHUTDOWN within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and be in at least COLD SHUTDOWN within the next 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
SURVEILLANCE REQUIREMENTS i
i 4.6.4.2 Each suppression pool-Reactor Building vacuum breaker shall be demonstrated OPERABLE:
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a.
At least once per 92 days by manually verifying that the q
vacuum breaker is free to open.
i b.
At least once per 18 months by:
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Ocmonstrating that the force required to open each vacuum l
breaker does not exceed 0.5 psid, and P
4 2.
Visual inspection.
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BRUNSWICK - UNIT 1 3/4 6-20 n
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CONTAlf84ENT SYSTEMS SUPPRESSION POOL - REACTOR BUILDING VACUUM BREAKERS
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LIMITING CONDITION FOR OPERATION
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.h 3.6.4.2 All suppression pool-Reactor ~ Building vacuum breakers shall be OPERABLE with an opening setpoint of < 0.5 psid with the manual valves closed. l 3
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APPLICABILITY: CONDITIONS 1, 2 and 3.
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'i-ACTION:
1:
a.With indication of a low drywell pressure alarm, record the dryvell pressure.
every 15 minutes.
- b. With the drywell pressure indicating -0.5 psia,the manual valves in the
.s) suppression pool-reactor building vacuum breaker lines shall be opened.
- c. The manual valves in the suppression pool-reactor building vacuum breaker lines shall be opened prior to operation of either the drywell or sup-pression pool spray systems.
d.If Actions a, b, or e above cannot be met, be in at least HOT SHUTDOWN within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and be in at least COLD SHUTDOWN within the next 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
j SURVEILLANCE REQUIREMENTS i
4.6.4.2 Each suppression pool-Reactor Building vacuum breaker shall be i.
demonstrated OPERABLE:
b At least once per 92 days by manually verifying that the a.
vacuum breaker is free to open.
b.
At least once per 18 months by:
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Demonstrating that the force required to open each vacuum breaker does not exceed 0.5 psid, and 2.
Visual inspection.
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