ML20141B856

Proposed Tech Specs,Revising Operability Requirements for Rod Block Monitor Sys

ML20141B856
Person / Time
Site:	Hatch
Issue date:	05/09/1997
From:	SOUTHERN NUCLEAR OPERATING CO.
To:
Shared Package
ML20141B837	List: HL-5362, Application for Amends to Licenses DPR-57 & NPF-5,revising Operability Requirements for Rod Block Monitor Sys ML20141B856
References
NUDOCS 9705160045
Download: ML20141B856 (22)

Text

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i Edwin I. Hatch Nuclear Plant Request to Revise Technical Specifications:

Rod Block Monitor Operability Requirements Page Change Instructions l

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l Unit 1 i

Eags ggy.htq_g 3.3 19 3.3-19 5.0-19 5.0-19 l

Unit 2 1

Eage Replace l

3.3-20 3.3-20 5.0-19 5.0-19 9705160045 970509 PDR ADOCK 05000321 P

PM HL-5362 E3-1

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Control Rod Block Instrumentation L

3.3.2.1 l

Table 3.3.2.1 1 (page 1 of 1)

Control Rod Block Instrumentation APPLICABLE I

MODES OR I-0THER j

SPECIFIED REQUIRED SURVE!LLANCE ALLOW 45LE l

FUNCTION CONDITIONS CHANNELS REQUIREMENTS VALUE l

l 1.

Rod Block Monitor a.

Low Power Range-Upscale (a) 2 st 3.3.2.1.1 s 115.5/125 st 3.3.2.1.4 divisions of SR 3.3.2.1.7 full scale b.

Intermediate Power (b) 2 SR 3.3.2.1.1

. s 109.7/125 Range - Upscale SR 3.3.2.1.4 divisions of SR 3.3.2.1.7 full scale c.

High Power Range-Upscale (c) 2 SR 3.3.2.1.1 s 105.9/125 I

sa 3.3.2.1.4 divisions of SR 3.3.2.1.7 full scale d.

Inop (d) 2

$R 3.3.2.1.1 NA I

e.

Downscale (d) 2 sa 3.3.2.1.1 2 93/125 l

SR 3.3.2.1.7 divisions of full scale I '),2(')

1 SR 3.3.2.1.2 NA

'1 I

2.

Rod Worth Minimiter SR 3.3.2.1.3 sa 3.3.2.1.5 sR 3.3.2.1.8 3.

Reactor Mode switch - shutdown (f) 2 sR 3.3.2.1.6 NA l

Position (a) THERMAL POWER R 29% and < 64% RTP.

(b) - THERMAL POWER R 64% and < 84% RTP.

(c) THERMAL POWER R 84%.

(d) THERMAL POWER R 29%.

(e) With THERMAL POWER < 10% RTP.

(f) Reactor mode switch in the shutdown position.

HATCH UNIT 1 ~

3.3-19 97-11-4/11/97

l 6

Control Rod Block Instrumentation 3.3.2.1 Table 3.3.2.1 1 (page 1 of 1) control Rod Block Instrumentation APPLICABLE I.

M@ES OR OTHER l

SPECIFIED REQUIRED SURVEILLANCE ALLOWASLE FUNCTION CONDITIONS CHANNELS REQUIREMENTS VALUE 1.

Rod stock Monitor s.

Low Power Range-Upscale (a) 2 SR 3.3.2.1.1 s 115.5/125 i

SR 3.3.2.1.4 divisions of

(

SR 3.3.2.1.7 full scale b.

Intermediate Power (b) 2 SR 3.3.2.1.1 s 109.7/125 Range - Upscale SR 3.3.2.1.4 divisions of SR 3.3.2.1.7 full scale c.

High Power Range -Upscale (c) 2 SR 3.3.2.1.1 s 105.9/125 SR 3.3.2.1.4 divisions of i

SR 3.3.2.1.7 full scale d.

Inop (d) 2 SR 3.3.2.1.1 NA I

e.

Downscale (d) 2 SR 3.3.2.1.1 2 93/125 SR 3.3.2.1.7 divisions of l

full scale 2.

Rod Worth Minimizer 1('),2(*)

1 SR 3.3.2.1.2 NA SR 3.3.2.1.3 g

SR 3.3.2.1.5 SR 3.3.2.1.8 3.

Reactor Mode Switch -Shutdown (f) 2 SR 3.3.2.1.6 NA Position (a) THERMAL POWER t 29% and < 64% RTP.

(b) THERMAL POWER t 64% and < 84% RTP.

(c) THERMAL POWER t 84%.

(d) THERMAL POWER t 29%.

(e) With THERMAL POWER < 10% RTP.

(f) Reactor mode switch in the shutdown position.

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HATCH UNIT 2 3.3-20 97-11-4/11/97

Reporting Requirements 5.6 i.

5.6 Reporting Requirements (continued) 5.6.5 CORE OPERATING LIMITS REPORT (COLR) a.

Core operating limits shall be established prior to each reload cycle, or prior to any remaining portion of a reload l

cycle, and shall be documented in the COLR for the following:

1)

The Average Planar Linear Heat Generation Rate for Specification 3.2.1.

2)

The Minimum Critical Power Ratio for Specification 3.2.2.

b.

The analytical methods used to determine the core operating limits shall be those previously reviewed and approved by the NRC, specifically those described in the following documents:

1)

NEDE-240ll-P-A, " General Electric Standard Application for Reactor Fuel," (applicable amendment specified in the COLR).

2)

" Safety Evaluation by the Office of Nuclear Reactor Regulation Supporting Amendment No. 157 to Facility Operating License DPR-57," dated September'12, 1988.

c.

The core operating limits shall be determined such that all applicable limits (e.g., fuel thermal mechanical limits, core thermal hydraulic limits, Emergency Core Cooling Systems (ECCS) limits, nuclear limits such as 50M, transient analysis limits and accident analysis limits) of the safety analysis are met.

d.

The COLR, including any mid-cycle revisions or supplements, shall be provided upon issuance for each reload cycle to the NRC.

l 4

(continued)

HATCH UNIT 1 5.0-19 97-11-4/11/97

Reporting Requirements 5.6

)

5.6 Reporting Requirements (continued) 5.6.5 CORE OPERATING LIMITS REPORT (COLR) a.

Core operating limits shall be established prior to each reload cycle, or prior to any remaining portion of a reload cycle, and shall be documented in the COLR for the j

following:

1)

The Average Planar Linear Heat Generation Rate for Specification 3.2.1.

2)

The Minimum Critical Power Ratio for Specification 3.2.2.

b.

The analytical methods used to determine the core operating limits shall be those previously reviewed and approved by the NRC, specifically those described in the following documents:

1)

NEDE-240ll-P-A, " General Electric Standard Application j

for Reactor Fuel," (applicable amendment specified in the COLR).

2)

" Safety Evaluation by the Office of Nuclear Reactor Regulation Supporting Amendment Nos.151 and 89 to Facility Operating Licenses DPR-57 and NPF-5," dated January 22, 1988.

1 c.

The core operating limits shall be determined such that all applicable limits (e.g., fuel thermal mechanical limits, core thermal hydraulic limits, Emergency Core Cooling Systems (ECCS) limits, nuclear limits such as SDM, transient analysis limits and accident analysis limits) of the safety analysis are met, d.

The COLR, including any mid-cycle revisions or supplements, shall be provided upon issuance for each reload cycle to the NRC.

i (continued) l HATCH UNIT 2 5.0-19 97-11-4/11/97

_ _ _ _. ~... _. _ _ _.. _. _ _

d Control Red Block Instrumentation 3.3.2.1

}

Table 3.3.2.1 1 (page 1 of 1)

Control Rod Block Inst w tation APPLICA8LE 4

4 MODES OR OTNH SPECIF1 3 REQUIRED SURVEILLANCE ALLOWABLE FUNCTION CONo!TIONS CHANNELS REQUIREMENTS VALUE 1.

Rod Block Monitor a.

Low Power Range-Upecats (a) 2 SR 3.3.2.1.1 5 115.5/125 SR 3.3.2.1.4 divisions of SR 3.3.2.1.7 felt scale b.

Intermodlate Power (b) 2 SR 3.3.2.1.1 s 109.7/125 Range - upscale st 3.3.2.1.4 divisions of SR 3.3.2.1.7 futt scate c.

High Power Range-Upscale (c) Ae 2

SR 3.3.2.1.1 s 105.9/125 SR 3.3.2.1.4 divisions of SR 3.3.2.1.7 futt seate d.

Inop (d)de 2

SR 3.3.2.1.,1 NA e.

Downscale (d),fe9-2 sa 3.3.2.1.1 t 93/125 st 3.3.2.1.7 divisions of futt scale

@ GO 2.

Rod Worth Minimizer 1$2M i

st 3.3.2.1.2 NA st 3.3.2.1.3 st 3.3.2.1.5 st 3.3.2.1.8 3.

Reactor Mode switch,ehutdown w

2 st 3.3.2.1.6 NA Position i

(a) THERMAL POWER t 29% and < 64% RTP.

7^.,.

(b) THERMAL POWER t 641 and < 84% RT7 d

~.

".M.

(c) THERMAL POWER t 84% rd ' ^^" "** rd ;. ;

• M.-

'e M;'A. 7%';

^C ;;?

4; ^,, ".O.

)M THERtEL POWER t 29% rd ' ^^~ "*" rd :.;,

" M.

@)4+1 With THERMAL POWER w 101 RTP.

(et' Reactor mode switch in the shutdown position.

HATCH UNIT 1 3.3-19 Proposed Amendment No. 7/16/96 i

Reporting Requirements 5.6 t

5.6 Reporting Requirements (continued) 5.6.5

-CORE OPERATING LIMITS REPORT (COLR) i a.-

Core operating limits shall be established prior to each reload cycle, or prior to any remaining portion of a reload l

cycle, and shall be documented in the COLR for the following:

i 1)

C::tr:1 R:d 3100k In:tr;;;;t: tion n:d Sleck ". nit:r for S;;;;ificati;r. 3.3.2.1.

I L

1) 4}- The Average Planar Linear Heat Generation Rate for L

Specification 3.2.1.

7-) 4}~ The Minimum Critical Power Ratio for Specifications L

3.2.2,:nd 3.2.2.1.

b.

The analytical methods used to determine the core operating j

limits shall be those previously reviewed and approved by the NRC, specifically those described in the following documents:

1)

NEDE-24011-P-A, " General Electric Standard Application l

for Reactor Fuel," (applicable amendment specified in the COLR).

2)

" Safety Evaluation by the Office of Nuclear Reactor Regulation Supporting Amendment No.157 to Facility l

Operating License DPR-57," dated September 12, 1988.

l-c.

The core operating limits shall be determined such that all l

applicable limits (e.g., fuel thermal mechanical limits, core thermal hydraulic limits, Emergency Core Cooling Systems (ECCS) limits, nuclear limits such as SDM, transient l

analysis limits and accident analysis limits) of the safety analysis are met.

d.

The COLR, including any mid-cycle revisions or supplements, shall be provided upon issuance for each reload cycle to the NRC.

i-4 k

j (continued)

J I

l HATCH UNIT 1 5.0-19 Amendment No. 195 l

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Control Rod Block Instrumentaticn 3.3.2.1 Table 3.3.2.1 1 (pese 1 of 1)

(

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control Rod stock Instrumentation 1

APPLICAsLE N0EEs OR OTNER i

sPECIFIED REQUIRED SURVEILLANCE ALLOWASLE' i

FUNCTION CONDITIONS CHANNELS REQUIREMENTS VALUE i

1.

Rod Block Monitor a.

Lou Power Range-Upscale (a) 2 sa 3.3.2.1.1 s 115.5/125 SR 3.3.2.1.4 divisions of SR 3.3.2.1.7 futt scate b.

Intenmediate Power (b) 2 sa 3.3.2.1.1 s 109.7/125 Range - upscale SR 3.3.2.1.4 divisions of st 3.3.2.1.7 futt scale c.

Nish Power Range-Upscale (c)ffdt-2 sa 3.3.2.1.1 s 105.9/125 st 3.3.2.1.4 divisions of sR 3.3.2.1.7 futt scate d.

Inop (d),44-2 st 3.3.2.1.1 NA e.

Dounscale (d)M 2

sa 3.3.2.1.1 t 93/125 sa 3.3.2.1.7 divisions of 1

futt scale 2.

Rod Worth Minimizer 1N,2N 1

sa 3.3.2.1.2 NA sa 3.3.2.1.3 SR 3.3.2.1.5 st 3.3.2.1.8 (b

3.

Reactor Mode switch -shutdown te 2

SR 3.3.2.1.6 NA Position

.=

(s) THERMAL POWER t 29% and < 64% RTP eneHIGPR"T"f"7(T.

(b) THERMAL POWER R 64% and < 84% RTP W 5 "", ;.7G.

(c) THERMAL POWER t 84% W ' ^^" 077 enu m.m < i.is.

= mm mu u :T-e

.w.

(sD(et THERMAL POWER t 29% h : = 77 d -ra 4 1.7G.

(6dM9 With THERMAL POWER < 10% RTP.

(f)(e-Reactor mode switch in the shutdown position.

HATCH UNIT 2 3.3-20 Amendment No. 146

/

j Reporting Requirements 5.6 5.6 Reporting Requirements (continued) l 5.6.5 CORE OPERATINGj R TS REPORT (COLR)

Core operating limits shall be established prior to each a.

reload cycle, or prior to any remaining portion of a reload cycle, and shall be documerted in the COLR for the following:

1 1)

Cudivi Rud Biv a In diuuientation - Red Sicck "enitor Te. Spec Tication 0.0.2.1.

i

1) - The Average Planar Linear Heat Generation Rate for Specificatio'n 3.2.1.

2) -St The Minimum Critica' Power Ratio for Specifications 3.2.2.ar.d 3.3.2.1.

b.

The analytical methods ust ! to determine the core operating limits shall be those prev. Isly reviewed and approved by the NRC, specifically those described in the following documents:

1)

NEDE-24011-P-A, " General Electric Standard Application for Reactor Fuel," (applicable amendment specified in the COLR).

i 2)

" Safety Eva1La. ion by the Office of Nuclear Reactor 1

Regulation Supporting Amendment Nos. 151 and 89 to Facility f/ prating Licenses DPR-57 and NPF-5," dated January 22, 1988.

c.

The core operating limits shall be determined such that all applicable limits (e.g., fuel thermal mechanical limits,

)

cor's thermal hydraulic limits, Emergency Core Cooling Systems (ECCS) limits, nuclear limits such as SDM, transient analysis limits and accident analysis limits) of the safety analysis are met.

d.

The COLR, including any mid-cycle revisions or supplements, shall be provided upon issuance for each reload cycle to the NRC.

l l

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(continued)

HATCH UNIT ;

5.0-19 Amendment No. 135

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Edwin I. Hatch Nt. clear Plant Request to Revise Technical Specifications:

Rod Block Monitor Operability Requirements Bases Changes Unit 1 EASC ECRlaC#

B 3.3-42 B 3.3-42 B 3.3-45 B 3.3-45 Unit 2 EagC Reolace B 3.3-42 B 3.3-42 B 3.3-45 B 3.3-45

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HL-5362 E4-1

Control Rod Block Instrumentaticn B 3.3.2.1 B 3.3 INSTRUMENTATION B 3.3.2.1 Control Rod Block Instrumentation BASES i

-BACKGROUND Control rods provide the primary means for control of reactivity changes.

Control rod block instrumentation includes channel sensors, logic circuitry, switches, and relays that are designed to ensure that the fuel cladding

^

integrity safety limit, and specified fuel design limits are not violated during postulated transients and accidents.

During high power operation, the rod block monitor (RBM) provides protection for control rod withdrawal error events.

3 During low power operations, control rod blocks from the rod worth minimizer (RWM) enforce specific control rod sequences designed to mitigate the consequences of the control rod i

drop accident (CRDA).

During shutdown conditions, control rod blocks from the Reactor Mode Switch - Shutdown Position q

Function ensure that all control rods remain inserted to prevent inadvertent criticalities.

The purpose of the RBM is to limit control rod withdrawal if localized neutron flux exceeds a predetermined setpoint during control rod manipulations.

It is' assumed to function 1

to block further control rod withdrawal to preclude a i

violation of the MCPR Safety Limit (SL) or a specified acceptable fuel design limit (SAFDL). The RBM supplies a trip signal' to the Reactor Manual Control System (RMCS) to appropriately inhibit control rod withdrawal during power operation above the low power range setpoint.

The RBM has two channels, either of which can initiate a control rod block when the channel output exceeds the control rod block setpoint. One RBM channel inputs into one RMCS rod block circuit and the other RBM channel inputs into the second RMCS rod block circuit.

l The RBM channel signal is generated by aversging a set.of local power range monitor (LPRM) signals at various core heights surrounding the control rod being withdNwn. A signal from one of the four redundant average power range monitor (APRM) channels supplies a reference signal for one of the RBM channels, and a signal from another of the APRM channels supplies the reference signal to the second RBM channel. This reference signal is used to determine which RBM range setpoint (low, intermediate, or high) is enabled.

If the APRM is indicating less than the low power range setpoint, the RBM is automatically bypassed. The RBM (continued)

HATCH UNIT 1 B 3.3-42 RBM 4/97

o Control Rod Block Instrumentation B 3.3.2.1 BASES BACKGROUND is also automatically bypassed if a peripheral control (continued) rod is selected (Ref.1). A rod block signal is also generated if an RBM Downscale trip or an Inoperable trip occurs. The Downscale trip will occur if the RBM channel signal decreases below the Downscale trip setpoint after the RBM signal ha been normalized. The Inoperable trip will occur during the nulling (nanaalization) sequence, if:

the RBM channel fails to null, too few LPRM inputs are available, a module is not plugged in, or the function switch is moved to any position other than " Operate."

The purpose of the RWM is to control rod patterns during startup and shutdown, such that only specified control rod sequences and relative positions are allowed over the operating range from all control rods inserted to 10% RTP.

The sequences effectively limit the potential amount and l

rate of reactivity increase during a CRDA.

Prescribed control rod sequences are stored in the RWM, which will initiate control rod withdrawal and insert blocks when the actual sequence deviates beyond allowances from the stored sequence. The RWM determines the actual sequence based position indication for each control rod. The RWM also uses feedwater flow and steam flow signals to determine when the reactor power is above the r 9 set power level at which the RWM is automatically bypasssa.'Ref. 2).

The RWM is a single channel system that provides input into both RMCS rod block circuits.

With the reactor mode switch in the shutdown position, a i

control rod withdrawal block is applied to all control rods to ensure that the shutdown condition is maintained. This function prevents inadvertent criticality as the result of a control rod withdrawai' during MODE 3 or 4, or during MODE 5 when the reactor mode switch is required to be in the shutdown position.

The reactor mode switch has two channels, each inputting into a separate RMCS rod block circuit. A rod block in either RMCS circuit will provide a control rod block to all control rods.

4 (continued)

HATCH UNIT 1 B 3.3-43 RBM 4/97

Control Rod Block Instrume" ation B s.3.2.1 1

BASES APPLICABLE 1.

Rod Block Monitor (continued)

SAFETY ANALYSES, LCO, and effects (for channels that must function in harsh APPLICABILITY environments as defined by 10 CFR 50.49) are accounted for.

The RBM is assumed to mitigate the consequences of an RWE event when operating 2: 29% RTP. Below this power level, the consequences of an RWE event will not violate the MCPR SL or the 1% plastic strain design limit; therefore, the RBM is not required to be OPERABLE (Ref. 3).

2.

Rod Worth Minimizer The RWM enforces the banked position withdrawal sequence-(BPWS) to ensure that the initial conditions of the CRDA analysis are not violated. The analytical methods and assumptions used in evaluating the CRDA are summarized in References 4, 5, 6, and 7.

In addition, the Reference 6 analysis (Generic BPWS analysis) may be modified by plant specific evaluations. The BPWS requires that control rods be moved in groups, with all control rods assigned to a specific group required to be within specified banked positions. Requirements that the control rod sequence is in compliance with the BPk'S are specified in LC0 3.1.6, " Rod Pattern Control."

The RWM Function satisfies Criterion 3 of the NRC Policy Statement (Ref. 10).

Since the RWM is a system designed to act a's a backup to operator control of the rod sequences, only one channel of the RWM is available and required to be OPERABLE (Ref. 7).

Special circumstances provided for in the Required Action of LC0 3.1.3, " Control Rod OPERABILITY," and LC0 3.1.6 may necessitate bypassing the RWM to allow continued operation with inoperable control rods, or to allow correction of a control rod pattern not in compliance with the BPWS. The (continued)

HATCH UNIT 1 B 3.3-45 97-11-4/11/97

Centrol Rod Block Instrumentation B 3.3.2.1 l

B 3.3 INSTRUMENTATION B 3.3.2.1 Control Rod Block Instrumentation BASES BACKGROUND Control rods provide the primary means for control of reactivity changes.

Control rod block instrumentation includes channel sensors, logic circuitry, switches, and relays that are designed to ensure that the fuel cladding integrity safety limit (SL), and the specified fuel design limits are not violated during postulated transients and accidents. During high power operation, the rod block monitor (RBM) provides protection for control rod withdrawal error events. During low power operations, control rod blocks from the rod worth minimizer (RWM) enforce specific control rod sequences designed to mitigate the consequences of the control rod drop accident (CRDA). During shutdown conditions, control rod blocks from the Reactor Mode Switch - Shutdown Position Function ensure that all control rods remain inserted to prevent inadvertent criticalities.

The purpose of the RBM is to limit control rod withdrawal if localized neutron flux exceeds a predetermined setpoint during control rod manipulations.

It is assumed to func. tion to block further control rod withdrawal to preclude a violation of the MCPR SL or a specified acceptable fuel design limit (SAFDL). The RBM supplies a trip signal to the RMCS) to appropriately Reactor Manual Control System (during power operation above inhibit control rod withdrawal the low power range setpoint.

The RBM has two channels, either of which can initiate a control rod block when the 4

channel output exceeds the control rod block setpoint. One RBM channel inputs into one RMCS rod block circuit and the i

other RBM channel inputs into the second RMCS rod block l

circuit.

The RBM channel signal is generated by averaging a set of i

local power range monitor (LPRM signals at various core heights surrounding the control) rod being withdrawn.A signal from one of the four redundant average power range monitor (APRM) channels supplies a reference signal for one of the RBM channels, and a signal from another of the RBM channels supplies the reference signal to the second RBM channel. This reference signal is used to determine which RBM range setpoint (low, intermediate, or high) is enabled.

If the APRM is indicating less than the low power range setpoint, the RBM is automatically bypassed. The RBM is l

also automatically bypassed if a peripheral control rod is (continued)

HATCH UNIT 2 B 3.3-42 97-11-4/11/97

Control Rod Block Instrumentation l

B 3.3.2.1 BASES BACKGROUND selected (Ref.1). A rod block signal is also generated if (continued) an RBM Downscale trip or an Inoperable trip occurs. The Downscale trip willoccur if the RBM channel signal decreases below the Downscale trip setpoint after the RBM signal has been normalized. The Inoperable trip will occur during the i

nulling (normalization) sequence, if:

the RBM channel i

fails to null, too few LPRM inputs are available, a module is not plugged in, or the function switch is moved to any position other than " Operate."

The purpose of the RWM is to control rod patterns during startup and shutdown, such that only specified control rod sequences and relative positions are allowed over the operating range from all control rods inserted to 10% RTP.

The sequences effectively limit the potential amount and rate of reactivity ir. crease during a CRDA.

Prescribed control rod sequences are stored in the RWM, which will initiate control rod withdrawal and insert blocks when the actual sequence deviates beyond allowances from the stored sequence.

The RWM determines the actual sequence based position indication for each control rod. The RWM also uses feedwater flow and steam flow signals to determine when the reactor power is above the preset power level at which the RWM is automatically bypassed (Ref. 2). The RWM is a single channel system that provides input into both RMCS rod block circuits.

With the reactor mode switch in the shutdown position, a control rod withdrawal block is applied to all control rods to ensure that the shutdown condition is maintained. This Function prevents inadvertent criticality as the result of a control rod withdrawal during MODE 3 or 4, or during MODE 5 l

when the reactor mode switch is required to be in the shutdown position. The reactor mode switch has two channels, each inputting into a separate RMCS rod block l

circuit. A rod block in either RMCS circuit will provide a l

control rod block to all control rods.

l l

t (continued)

HATCH UNIT 2 8 3.3-43 97-11-4/11/97 l

Control Rod Block Instrumentation B 3.3.2.1 l

BASES APPLICABLE 1.

Rod Block Monitor (continued)

SAFETY ANALYSES, 4

LCO, and effects (for channels that must function in harsh l'

APPLICABILITY environments as defined by 10 CFR 50.49) are accounted for.

The RBM is assumed to mitigate the consequences of an RWE event when operating a 29% RTP.

Below this power level, the consequences of an RWE event will not violate the MCPR SL or the 1% plastic strain design limit; therefore, the RBM is not required to be OPERABLE (Ref. 3).

2.

Rod Worth Minimizer The RWM enforces the banked position withdrawal sequence (BPWS) to ensure that the initial conditions of the CRDA analysis are not violated. The analytical methods and assumptions used in evaluating the CRDA are summarized in References 4, 5, 6, and 7.

In addition, the Reference 6 analysis (Generic BPWS analysis) may be modified by plant specific evaluations. The BPWS requires that control rods i

be moved in groups, with all control rods assigned to a i

specific group required to be within specified banked positions. Requirements that the control rod sequence is in compliance with the BPWS are specified in LC0 3.1.6, " Rod Pattern Control."

i The RWM Function satisfies Criterion 3 of the NRC Policy Statement (Ref. 10).

Since the RWM is a system designed to act as a backup to operator control of the rod sequences, only one channel of the RWM is available and required to be OPERABLE (Ref. 7).

Special circumstances provided for in the Required Action of LCO 3.1.3, " Control Rod OPERABILITY," and LC0 3.1.6 may i

necessitate bypassing the RWM to allow continued operation i

with inoperable control rods, or to allow correction of a control rod pattern not in compliance with the BPWS. The i

l 1

(continued) i HATCH UNIT 2 B 3.3-45 DOCR 97-11-4/11/97

i f

,a 8 4 Control Rod Block Instrumentation B 3.3.2.1 B 3.3 INSTRUMENTATION B 3.3.2.1 Control Rod Block Instrumentation i

BASES 4

BACKGROUND Control rods provide the primary means for control of reactivity changes. Control rod block instrumentation

_ d includes channel sensors, logic circuitry, switches, and

/4e [ue/ C/ add'M relays that are designed to ensure that4specified fuel jg fega// M 7

desis n limits are not;;;;;;d:d fr postulated transients and 7

accic ents. During high power operation, the rod block l'.'"'f> o,,d monitor (RBM) provides protection for control rod withdrawal error events. During low power operations, control rod blocks from the rod worth minimizer (RWM) enforce specific V/oh[ed control rod sequences designed to mitigate the consequences dd/h of the control rod drop accident (CRDA). During shutdown conditions, control rod blocks from the Reactor Mode 1

Switch - Shutdown Position Function ensure that all control rods remain inserted to prevent inadvertent criticalities.

The purpose of the RBM is to limit control rod withdrawal if localized neutron flux exceeds a predetermined setpoint g f/a)/o n durina control rod manipulations.

It is assumed to function to block further control rod withdrawal to preclude 4MCPR 0[ MC SafetyLimit(SLpiclaticr..

The RBM supplies a trip signal to the Reactor Manual Control System (RMCS) to appropriately inhibit control rod withdrawal during power operation above the low power range setpoint. The RBM has two channels, i

either of which can initiate a control rod block when the O R " V*^ 8'.

channel output exceeds the control rod block setpoint. One M /e he/< RBM channel inputs into one RMCS rod block circuit and the accer d63d6 j' * # f

'j other RBM channel inputs into the second RMCS rod block circuit.

l (SA FDL.)

The RBM channel signal is generated by averaging a set of local power range monitor (LPRM) signals at various core heights surrounding the control rod being withdrawn. A signal from one of the four redundant average power range monitor (APRM) channels supplies a reference signal for one of the RBM channels, and a signal from another of the APRM channels supplies the reference signal to the second RBM channel.

This reference signal is used to determine which RBH range setpoint (low, intermediate, or high) is enabled.

l If the APRM is indicating less than the low power range setpoint, the RBM is automatically bypassed. The RBM is also automatically bypassed if a peripheral control i

rod is selected (Ref. 1). A rod block signal is also l

j (continued)

HATCH UNIT 1 B 3.3-42 PROPOSED REVISION 7/16/96

,a Control Rod Block Instrumentation B 3.3.2.1 BASES l

l BACKGROUND generated if an RBM Downscale trip or an Inoperable trip l

(continued) occurs.

The Downscale trip will occur if the RBM channel l

signal decreases below the Downscale trip setpoint after the RBM signal has been normalized. The Inoperable trip will occur during the nulling (normalization) sequence, if: the RBM channel fails to null, too few LPRM inputs are available, a module is not plugged in, or the function switch is moved to any position other than " Operate."

The purpose of the RWM is to control rod patterns during startup and shutdown, such that only specified control rod sequences and relative positions are allowed over the operating range from all control rods inserted to 10% RTP.

The sequences effectively limit the potential amount and rate of reactivity increase during a CRDA.

Prescribed control rod sequences are stored in the RWM, which will initiate control rod withdrawal and insert blocks when the actual sequence deviates beyond allowances from the stored sequence. The RWM determines the actual sequence based position indication for each control rod. The RWM also uses feedwater flow and steam flow signals to determine when the reactor power is above the preset power level. at which the RWM is automatically bypassed (Ref. 2).

The RWM is a single channel system that provides input into both RMCS rod block circuits.

With the reactor mode switch in the shutdown position, a control rod withdrawal block is applied to all control rods to ensure that the shutdown condition is maintained. This Function prevents inadvertent criticality as the result of a control rod withdrawal during MODE 3 or 4, or during MODE 5 when the reactor mode switch is required to be in the shutdown position.

The reactor mode switch has two channels, each inputting into a separate RMCS rod block circuit. A rod block in either RMCS circuit will provide a control rod block to all control rods.

l l

l (continued)

HATCH UNIT 1 B 3.3-43 PROPOSED REVISION 7/16/96

,, a Control Rod Block Instrumentation B 3.3.2.1 BASES APPLICABLE 1.

Rod Block Moni.t_gr (continued)

SAFETY ANALYSES, LCO, and effects (for channels that must function in harsh l

APPLICABILITY environments as defined by 10 CFR 50.49) are accounted for.

G The RBM is assumed to mitigate the consequences of an RWE Levent when operatinc 2: 29% RTP.

Below this power level, the i

gy phe, l 7. q consequences of an FWE event will nof"==d the MCPR SL g

A(Ref. 3).

"h= :p;r: ting : 00% R.. ired to be OPERABLE therefore, the RBM is not reg :=ly:::

f l a M i c.5 b, n (R:f. 3) h":

1 def ch= tht with = initi:1 "CPR t 1.70, :: PSE==t util U ']" Ib 4 l

r =lt in== ding the "CPR SL. A1:0, th: =:ly::: -

i = r.:tr:t: th t.:h= :p;r: ting :t t 95 RTP with "CPR e.1.40, ne R": event will reewit in e seed-;ng tl,e MCPR SL (Ref. 3). T h r fert, = der th::: :=diti=:, th Pa", i:-

i 1

- :1= =t r: sir:d to k OPEPOLET i

2.

Rod Worth Minimizer The RWM enforces the banked position withdrawal sequence (BPWS) to ensure that the initial conditions of the CRDA analysis are not violated. The analytical methods and assumptions used in evaluating the CRDA are summarized in j

References 4, 5, 6, and 7.

In addition, the Reference 6 analysis (Generic BPWS analysis) may be modified by plant specific evaluations. The BPWS requires that control rods be moved in groups, with all control rods assigned to a s

specific group required to be within specified banked positions. Requirements that the control rod sequence is in compliance with the BPWS are specified in LCO 3.1.6, " Rod Pattern Control."

The RWM Function satisfies Criterion 3 of the NRC Policy Statement (Ref. 10).

Since the RWM is a system designed to act as a backup to operator control of the rod sequences, only one channel of the RWM is available and required to be OPERABLE (Ref. 7).

Special circumstances provided for in the Required Action of LCO 3.1.3, " Control Rod OPERABILITY," and LCO 3.1.6 may necessitate bypassing the RWM to allow continued operation with inoperable control rods, or to allow correction of a control rod pattern not in compliance with the BPWS. The (continued)

HATCH UNIT 1 B 3.3-45 REVISION 0

j W

Control Rod Block Instrumentation B 3.3.2.1 I

B 3.3 INSTRUMENTATION f'

l B 3.3.2.1 Control Rod Block Instrumentation BASES l

BACKGROUND Control rods provide the primary means for control of j

i reactivity changes. Control rod block instrumentation includes _ channel sensors, logic circuitry, switches, and i

Q/g 4 /. c4c&j relays that are designed to ensure that7specified fuel i

/n fey'.#/ S4j/

design limits are nota:::::dd fer postulated transients and

/,;n ; /, a n d-monitor (RBM) provides protection for control rod withdrawal

, T dehts. DuFing high power operation, the rod block error events. During low power operations, control rod l

l blocks from the rod worth minimizer (RWM) enforce specific y;dded daog)i

~ control rod sequences designed to mitigate the consequences i

of the control rod drop accident (CRDA). Duris.g shutdown l

conditions, control rod blocks from the Reactor Mode Switch - Shutdown Position Function ensure that all control rods remain inserted to prevent inadvertent criticalities, i

a i

i The purpose of the RBM is to limit control rod withdrawal if

, g f

localized neutron flux exceeds a predetermined setpoint V/

d It_is_assumtd_ttfunction of W j% uringJ;ontroLrod_ manipulations-to block further control rod withdrawal to p

(

l Safety Limit (SL)pi:htt:. The RBM supplies a trip signal j

To the Reactor Manual Control System (RMCS) to appropriately

~

inhibit control rod withdrawal during power operation above the low power range setpoint.

The RBM has two channels, either of which can initiate a control rod block when the j

gy Yu,/;eg channel output exceeds the control rod block setpoint. One acce/@ M RBM channel inputs into one RMCS rod block circuit and the g,, /,mff other RBM channel inputs.into.the.second RMCS rod block circuit.

g The RBM channel signal is generated by averaging a set of 4

local power range monitor (LPRM) signals at various core heights surrounding the control rod being withdrawn. A i

signal from one of the four redundant average power range monitor (APRM) channels supplies a reference signal for one of the RBM channels, and a signal from another of the APRM

)

J i

channels supplies the reference signal to the second RBM channel.

This reference signal is used to determine which RBM range setpoint (low, intermediate, or high) is enabled.

If the APRM is indics. ting less than the low power range i

setpoint, the RBM is automatically bypassed.

The RBM is 4

also automatically bypassed if a peripheral control rod is selected (Ref. 1). A rod block signal is also generated if i

(continued)

HATCH UNIT 2 B 3.3-42 REVISION 14 4

<u Control Rod Block Instrumentation B 3.3.2.1 I

BASES BACKGROUND selected (Ref. 1). A rod block signal is also generated if (continued) an RBM Downscale trip or an Inoperable trip occurs. The Downscale trip willoccur if the RBM channel signal decreases below the Downscale trip setpoint after the RBM signal has l

been normalized. The Inoperable trip will occur during the nulling (normalization) sequence, if:

the RBM channel fails to null, too few LPRM inputs are available, a module is not plugged in, or the function switch is moved to any i

position other than " Operate."

The purpose of the RWM is to control rod patterns during startup and shutdown, such that only specified control rod sequences and relative positions are allowed over the operating range from all control rods inserted to 10% RTP.

The sequences effectively limit the potential amount and rate of reactivity increase during a CRDA.

Prescribed control rod sequences are stored in the RWM, which will initiate control rod withdrawal and insert blocks when the actual sequence deviates beyond allowances from the stored sequence. The RWM determines the actual sequence based position indication for each control rod. The RWM also uses feedwater flow and steam flow signals to determine when the reactor power is above the preset power level at which the RWM is automatically bypassed (Ref. 2).

The RWM is a single channel system that provides input into both RMCS rod block circuits.

With the reactor mode switch in the shutdown position, a control rod withdrawal block is applied to all control rods to ensure that the shutdown condition is maintained. This Function prevents inadvertent criticality as the result of a control rod withdrawal during MODE 3 or 4, or during MODE 5 when the reactor mode switch is required to be in the shutdown position. The reactor mode switch has two channels, each inputting into a separate RMCS rod block circuit. A rod block in either RMCS circuit will provide a control rod block to all control rods.

I (continued)

HATCH UNIT 2 B 3.3-43 97-11-4/11/97 l

.. _. _. _. _ _ _ _ ~ _ _ _ _ _ _ _ _. _ _ _

o U.

Control Rod Block Instrumentation B 3.3.2.I BASES APPLICABLE 1.

Rod Block Monitor (continued)

SAFETY ANALYSES, LCO, and effects (for channels that must function in harsh i

APPLICABILITY environments as defined by 10 CFR 50.49) are accounted for.

hIONb The RBM is assumed to mitigate the consequences of an RWE even_t when operatina m 29% RTP.

Below this power level, the r

or the },/

consequences of an RWE event will noT'-enseed the MCPR SL l

h*NK NN4

% 4nds therefore, the RBM is not required to be OPERABLE (Ref. 3).

"h= :;:r: tin; < "' m, r:!y::: (P.:f. 2) 5-":-

g;

\\Mitjb

'r::h:;. th:t with n initi;l "CP", t 1.70, n; P"

^;ct will Id

=lt in :== ding th: "CPP, S'..

^1 =, th: =:l ":=

t n = tr:t: th:t d x :;;r:t';; :t :. ^^" P,TP ith MCin g.3,,, p (.....t

}i. g 't j, g ;;di.- th ( {

3_ l "T i ! I'.', m' '_'T '_ _1 "L! ' o;"'1 '". ""' ' ' ' '"' ' -"' "- ' '

I i

2.

Rod Worth Minimizer l

The RWM enforces the banked position withdrawal sequence (BPWS) to ensure that the initial conditions of the CRDA analysis are not violated. The analytical methods and l

assumptions used in evaluating the CRDA are summarized in References 4, 5, 6, and 7.

In addition, the Reference 6 analysis (Generic BPWS analysis) may be modified by plant specific evaluations. The BPWS requires that control rods be moved in groups, with all control rods assigned to a specific group required to be within specified banked positions. Requirements that the control rod sequence is in compliance with the BPWS are specified in LCO 3.1.6, " Rod Pattern Control."

The RWM Function satisfies Criterion 3 of the NRC Policy Statement (Ref. 10).

Since the RWM is a system designed to act as a backup to operator control of the rod sequences, only one channel of the RWM is available and required to be OPERABLE (Ref. 7).

Special circumstances provided for in the Required Action of LCO 3.1.3, " Control Rod OPERABILITY," and LCO 3.1.6 may necessitate bypassing the RWM to allow continued operation with inoperable control rods, or to allow correction of a control rod pattern not in compliance with the BPWS. The l

4 (continued)

HATCH UNIT 2 8 3.3-45 REVISION O l

_ _..., -