ML20211G745

Proposed Tech Specs Re Use of Sodium Pentaborate Enriched w/B-10 in Standby Liquid Control Sys

ML20211G745
Person / Time
Site:	Hatch
Issue date:	02/06/1987
From:	GEORGIA POWER CO.
To:
Shared Package
ML20211G734	List: ML20211G728 ML20211G745
References
TAC-64778, NUDOCS 8702250511
Download: ML20211G745 (5)

Text

LIMITING CONDITIONS FOR OPERATION SURVEILLANCE RE0ulRENENTS 3.4. STANDBY L10MID CONTROL SYSTEM 4.4. STAN08Y LIOUID CONTROL SYSTEM I Aeolicability Anoticability The Limiting Conditions for Opera- The Surveillance Requirements apply tion apply to the operating status to the periodic test and examination of the Standby Liquid Control of the Standby Liquid Control System.

System.

Ob.tective Objective The objective of the Limiting The objective of the Surveillance Conditions for Operation is to Requirements is to verify the oper-assure the availability of a ability of the Standby Liquid Control system with the capability to System.

shut down the reactor and main-tain the shutdown condition without the use of control rods.

Snecifications Snecifications A. Normal Svstem Availability A. Normal Doerational Tests During periods when fuel is The operability of the Standby in the reactor and prior to Liquid Control System shall be startup from the Cold Shut- verified by the performance of down Condition the standby the following tests:

Itquid control system shall be operable except:

1. When performing control rod 1. Monthly drive maintenance, at which At least once per month each time Specification 3.10.E. pump loop shall be locally shall be met, started and functionally tested by recirculating de-or mineralized water to the test tank.

2. When operating with an inoper- 2. Each Goeratina Cvele able component, at which time At least once during each oper-Specification 3.4.0. shall be ating cycle:-

met,

a. Check that the setting of or the system relief valve is 1325 ! 75 psig.

3. When the reactor is in the b. Verify that each pump will Cold Shutdown Condition and deliver 41.2 gpm against a aII control rods capable of system head of at least 1190 normal insertion are inserted psig.

and the requirements of Speci- c. Initiate one of the Standby fication 3.3.A. are met. Liquid Control System loops f rom the control room af ter arranging suction f rom the 1

test tank and pump dominer-

%2]311070206 P

geg 03coji, alized water into the reactor HATCH - UNIT 1 3.4-1

l 8ASES FOR LINITING CONDITIONS FOR OPERATION AN0 SURVEILLANCE REQUIRENENTS 3.4. STAN08Y L10010 CONTROL SYSTEM The standby liquid control (SLC) system provides a backup reactivity control capability to the control rod scram system. The original design l basis for the. standby liquid control system is to provide a soluble boron '

concentration to the reactor vessel sufficient to bring the reactor to a

cold shutdown. In addition to meeting its original design basis, the 4 system must also satisfy the requirements of the ATWS Rule 10 CFR 50.62 paragraph (c) (4), which requires that the system have a control capacity equivalent to that for a system with an injection rate of 86 gpm of 13 weight percent unenriched sodium pentaborate, normalized to a 251 inch diameter reactor vessel.

To meet its original design basis, the SLC system was designed with a

, sodium pentaborate solution tank, redundant pumps, and redundant explosive

! injection valves. The tank contains a sodium pentaborate solution of sufficient volume, concentration and 81* enrichment to bring the

, reactor to a cold shutdown. The solution is injected into the reactor  ;

j vessel using one of the redundant pumps.

The volume limits in Figure 3.4-1 are calculated such that for a given l concentration of sodium pentaborate, the tank contains a volume of solution

! adequate to bring the reactor to a cold shutdown, with margin. These j volume limits are based on gross volume and account for the unusable volume of solution in the tank and suction lines.

~

! To meet 10 CFR 50.62 Paragraph (c) (4), the system must have a reactivity i control capacity equivalent to that of a system with an 86 gpa injection <

i flow rate of 13 weight percent unenriched sodium pentaborate into a 251 j inch diameter reactor vessel. The term " equivalent reactivity control i capacity' refers to the rate at which the boron isotope B18 is injected into the reactor core. The standby liquid control system meets this  !

! requirement by using a sodium pentaborate solution enriched with a higher j j concentration of the 85* isotope. The minimum concentration limit of i 6.2 percent sodium pentaborate solution is based on 60 atomic percent  :

B18 enriched boron in sodium pentaborate and a flow rate of 41.2 gpe. l The method used to show equivalence with 10 CFR 50.62 is set forth in '

i NEDE-31096-P (Ref. 1),

i Limiting Conditions for Operation are established based on the redundancy j within the system and the reliability of the control rod scram system.

With the standby liquid control system inoperable, reactor operation for j short periods of time is justified because of the reliability of the control rod scram system. With one redundant component inoperable, reactor operation for longer periods of time is justified because the system could still fulfill its function.

Surveillance requirements are established on a frequency that assures a high system reliability. Thorough testing of the system each operating j cycle assures that the system can be actuated from the control room and I

will develop the flow rate required. Replacement of the explosive charges in the valves at regular intervals assures that these valves will not fail j due to deterioration of the charges. Functional testing of the pumps is j performed once per month to assure pump operability.

i I i l HATCH - UNIT I 3. 4 -4 1

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BASES FOR LINITING CON 0lfl0NS FOR OPERATION AND SURVEILLANCE REQUIRENENTS 3.4. STANOGY LIQUID CONTROL SYSTEN (Continued)

The sodium pentaborate solution is carefully monitored to assure its reactivity control capability is maintained. The enriched sodium pentaborate so1ution is made by mixing granular, enriched sodium pentaborate wi,th water. Isotopic tests on the granular sodium pentaborate are perforned to verify the actual 818 enrichment, prior to mixing with water. Once the enrichment is established, only the solution concentration, volume and temperature must be monitored to insure that an adequate amount of reactivity control is available.

Determining the solution concentration once per 31 days verifies that the solution has not been diluted with water. Checking the volume once each day will guard against noticeable fluid losses or dilutions, and daily temperature checks will prevent sodium pentaborate precipitation.

1. ' Anticipated Transients without scram, Response to NRC ATWS Rule, j 10 CFR 50.62", NEDE-31096-P, December 1985.

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! REGION OF REQUIRED VOLUME [

p CONCENTRATION FOR 2 60.0 l 0 11 ATOMIC PERCENT B10 ENRICHED l

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5 1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000 3200 3400 3600 3800 i GROSS VOLUME OF SOLUTION IN TANK (gal) i l FIGURE 3.41 SODIUM PENTABORATE SOLUTION VOLUME l l

VERSUS CONCENTRATION REQUIREMENTS 1 .

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, 6.2% m PERMISSIBLE REGION OF

_ OPERATION FOR 2 60.0

. E ATOMIC PERCENT 810 ENRICHED 100 SOOlUM PENTABORATE

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40 30 O 5 10 15 20 25 CONCENTRATION (WElGHT PERCENT SODIUM PENTABOR ATE IN SOLUTION)

FIGURE 3.4 2 SOOlUM PENTABOR ATE SOLUTION TEMPERATURE i VERSUS CONCENTRATION REQUIREMENTS

.- - -_-- . . . - _ - - _ _ _ - . _ - - ._.. _ _ _ _ _ - _ - . - _ . . _ _