ML20217B906

Proposed Tech Specs Re Control Rod Block Instrumentation

ML20217B906
Person / Time
Site:	Peach Bottom
Issue date:	10/01/1999
From:	PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:
Shared Package
ML20217B893	List: ML20217B889 ML20217B906
References
NUDOCS 9910130110
Download: ML20217B906 (5)

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Control Rod Block Instrumentation 3.3.2.1 l

, . Table 3.3.2.1 1 (page 1 of 1)

Control Rod Block Instrumentation APPLICABLE MODES OR OTHER SPECIFIED REQUIRED SURVE!LLANCE ALLOWABLE FUNCTION CONDITIONS CHANNELS REQUIREMENTS VALUE

1. Rod Block Monitor

a. Low Power Range-Upscale (a) 2 SR 3.3.2.1.1 (h)

SR 3.3.2.1.4 SR 3.3.2.1.5

b. Intermediate Power (b) 2 SR 3.3.2.1.1 (h)

Range - Upscale SR 3.3.2.1.4 SR 3.3.2.1.5 l c. High Power Range-Upscale (c) 2 SR 3.3.2.1.1 (h)

SR 3.3.2.1.4 SR 3.3.2.1.5

d. Inop (a) 2 SR 3.3.2.1.1 NA

2. Rod Worth Minimizer 1(II,2(I) 1 SR 3.3.2.1.2 NA j SR 3.3.2.1.3 i SR 3.3.2.1.6 SR 3.3.2.1.8

3. Reactor Mode Swltch - Shutdown (g) 2 SR 3.3.2.1.7 NA Position l(a) THERMAL POWER t 28.4% RTP and MCPR less than the limit specified in the COLR.

l(b) THERMAL POWER t 63.4% RTP and MCPR less than the limit speelffed in the COLR.

l(c) THERMAL POWER t 83.4% and MCPR less than the limit specified in the COLR.

l(d) Deleted.

l (e) Deleted.

(f) With THERMAL POWER 5 10% RTP.

(g) Reactor mode switch in the shutdown position.

(h) Less than or equal to the Allowable Value specified in the COLR.

l-l l 991013011o DR 99 toot ADOCK 05000277 PDR PBAPS UNIT 3 3.3-21 Amendment No.

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ATTACHMENT 3 l

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Control Rod Block Instrumentation 3.3.2.1

, . Table 3.3.2.1a1 (page 1 of 1)

Control Rod Block Instrumentation APPLICABLE MODES OR OTHER SPECIFIED REQUIRED SURVEILLANCE ALLOWABLE FUNCTION CONDITIONS CHANNELS REQUIREMENTS VALUE

1. Rod Block Monitor

a. Low Power Range- Upscale (a) 2 SR 3.3.2.1.1 (h)

SR 3.3.2.1.4 SR 3.3.2.1.5

b. Intermediate Power (b) 2 SR 3.3.2.1.1 (h)  !

Range - Upscale SR 3.3.2.1.4 SR 3.3.2.1.5 l c. High Power Range -Upscale (c) 2 SR 3.3.2.1.1 (h)

SR 3.3.2.1.4 i SR 3.3.2.1.5

d. Inop (a) 2 SR 3.3.2.1.1 NA

.l e. Downscale (a) 2 SR 3.3.2.1.1 (i)

SR 3.3.2.1.5 l

2. Rod Worth Minimizer 1(I) 2(I)

, 1 SR 3.3.2.1.2 NA SR 3.3.2.1.3 SR 3.3.2.1.6 SR 3.3.2.1.8

3. Reactor Mode Switch - Shutdown (g) 2 SR 3.3.2.1.7 NA ,

Position l l (a) THERMAL POWER t 28.4% RTP and MCPR less than the limit specified in the COLR.

l(b) THERMAL POWER t 63.4% RTP and MCPR less than the limit specified in the COLR.

l.(c) THERMAL POWER t 83.4% and MCPR less than the limit specified in the COLR.

l(d) f,eleted. l l (e) Deleted.

(f) With THERMAL POWER 5 10% RTP.

l (g) Reactor mode switch in the shutdown position. l I

(h) Less than or equal to the Allowable Value specified in the COLR. j (1) Greater than or equal to the Allowable Value specified in the C0tR.

l PBAPS UNIT 3 3.3-21 Amendment No.

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Control Rod Block Instrumentation B 3.3.2.1 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 specified fuel design limits'are not exceeded for 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 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 during control rod manipulations. It is. assumed to function to block further control rod withdrawal to preclude a MCPR

' Safety Limit-(SL) violation. 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 re. 51ock circuit. 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 redundtnt 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. l If the APRM is indicating less than the low power range j setpoint, the RBM is automatically bypassed. The RBM is

.also automatically bypassed if a peripheral control rod is selected (Ref.1). A rod block signal is also generated if an RBH downscale trip or an inoperable trip occurs, since this could indicate a problem with the RBM channel. The downscale trip will occur if the RBM channel signal 4 (continued)

-PBAPS UNIT 3 8 3.3-46 Revision No.

r Control Rod Block Instrumentation B 3.3.2.1 1

BASES l

f BACKGROUND decreases below the downscale trip setpoint after the RBM  !

f (continued) signal has been normalized. The inoperable trip will occur j if, during the nulling (normalization) sequence, the RBM  !

channel fails to null or too few LPRM inputs are available, I if a critical self-test fault has been detected, or the RBM instrument mode switch is moved to any position other than  ;

" Operate". '

The purpose of tne RWM is to control rod patterns during startup and shutdown, such that only specified control rod .

sequences and relative posit ons are allowed over the l operating range from all control rods inserted to 10% RTP. l The sequences effectively limit the potential amount and rate of reactivity increase during a CRDA. Prescribed control rud 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 j 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 1 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 t control rod withdrawal block is applied to all control rods I to ensure that the shutdown condition is maintained. This l 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.

APPLICABLE 1. Rod Block Monitor SAFETY ANALYSES, LCO, and The RBM is designed to prevent violation of the MCPR APPLICABILITY SL and the cladding 1% plastic strain fuel design limit that ,

may result from a single control rod withdrawal error (RWE) event. The analytical methods and assumptions used in evaluating the RWE event are summarized in Reference 1. A (continued)

PBAPS UNIT 3 8 3.3-47 Revision No.