ML20079P173

Forwards Response to Discussion Item 7 from 910906 Conference Call Re Rod Block Algorithm & Setpoint

ML20079P173
Person / Time
Site:	05000605
Issue date:	11/07/1991
From:	Marriott P GENERAL ELECTRIC CO.
To:	Pierson R NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), Office of Nuclear Reactor Regulation
References
MFN-142-91, NUDOCS 9111120264
Download: ML20079P173 (4)

Text

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4 CE Nuclear Energy November 7,1991 hiFN No.142 91 DocLet No. STN SNiO5 EEN 9179 Document Control Desk U.S. Nuclear Regulatory Comrnission Washington, D.C. 20555 Attention: itobert C. Pierson, Director Standardiration and Non.I'ower iteactor Project Directorate

Subject:

GE Response to GE/NRC Reactor Splem tiranch Conference Call of September 6,1991 Enclosed are thirty four (34) copies of the GE responses to Discussion item 7 (pertaining to rod block algorithm and set point) of the subject call.

It is intended that GE will incorporate this response in a future amendment.

Sinees ely, s

P.W. Marriott, Manager

- Regulatory and Analysis Services M/C 382, (408) 925 6948 -

ec: F. A. Ross (DOE)

N. D. Fletcher (DOE)

C. Poslusny, Jr. (NRC)

R. C. llerglund (GE) g J. F. Quirk (GE)

\u,\

9111120264 911107 PDR ADOCK 0500060L A PDR

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.ABWR -r Slin_dard Plant Rrv n two channel operability. The operator has scram time performance based on the scram the capability to invoke bypass conditions timing data received from the RC&lS.

within the following system or subsystems: g gyggg A 7.7.1.2.2 O'her Sptems Interfaces (a) Synchro A or E position bypass (t)) Rod server module channel A or B bypass (1) Alternate Rod Insertion (ATWS) (Anticipated (c) Uncoupled condition bypass Transient Without Scram)

(d) File control module channel A or B bypass The RC&lS logic, during an anticipated tran-(c) ARBht channel A or b bypass sient without scram (on receipt of signals (f) htRBhi channel A or B bypass as a result of high reactor dome pressure or (g) RPC channel A or B bypass low reactor water level) initiates ARI sig.

(b) RACS channel A or B bypass cals which controls the fine motion control (i) DAhi channel A or B bypass rod drive motors such that all control rods are driven to their full in position automa.

(11) Scram Time Test Data Recording tically. The four divisions of the nuclear boiler system provide each of the two The logic of the RC&lS provides tne capabi- channels of the RC&lS logic with the reacter lity to automatically record individval fine high dome pressure and reactor low water motion control rod drive (FhtCRD) scram level signals for generation of the ARI timing data based upon scram timing reed signal based on two out of four logic.

switches. When a particular PhiCRD scram timing switch is activated, the time of The operator at the RC&lS dedicated display actuation is recorded by D Ahls for time can take action and initiate the ARI func-tagging of stored scram tir. $ cst data for tion. Two manual actions are required to that particular fine motion cont al rod manually initiate ARI. The RC&lS logic has drive. The time tagged data is stored in been designed to complete the ARI functions i memory until the next actuation of that in the worst case non accident environment, l particular reed switch is detected again, completely independent of reactor pressure

transient conditions. This capability is The RC&lS also time tags the receipt of a accomplished with control logic for inser-reactor scram condition being a:tivated tion of all control rods by an alternate and based upon the scram following function diverse method, based on receiving reactor input signals from the reactor protection high dome pressure and low water level (Le-system which is received via the essential vel 2) signals for generating its own ATWS multiplexing systeru. (anticipated transient without scram) sig-nal. The logic of the RC&lS has been de-The resolution of this time tagging feature signed such that no single failure results is less than 10 milliseconds. Contact in failure to insert more than one operable bounce of the reed switch inputs and the DAh! control rod when the ARI function is inputs are properly masked to support this activated.

function. 'the reference real time clock for time tagging is the real time clock of the (2) Recirculation Flow Control Sptem RC&lS.

The recirculation flow control system (RFCS)

When RC&ls detects a reactor scram provides each of the two channels of the condition, the current position of all RC&lS with two separate isolated trip control rods in the core are recorded, time signals indicating the need for automatir ;,

l tagged, and stored in memory. RC&lS logic selected control rod tur .4 (SCRRI). The signals are treated as nonsafety related l$

i stores this data in mernory until a request I is aceived from the performance monitoring signals within the logic of the RC&lS.

and control system. The taansmitted data is used by the PhtCS to calculate and summarire The RFCS provides signals to both channels 1

Arnendment 3 7.1 17 i

• I N S G ST A (12) ATLM Algorithin Description The ATLM is a microprocessor based subsystem of RC&IS that executes tut dif ferent algoritluts for enforcing fuel operating therrnal limits. One algorithm enforces operating limit minimu:n critical power ratio (OMCPR), ani the other the operating limit minimum linear heat ge: . ration rate (OLMMcR),

For OMCPR algori.:hm, the cora is divided into 48 regions; each region consisting of 16 fuel bundles. For OLMMCR algorithin, each region is furthe vertically divided up into four segments. During a calculation cycle of ATL (about 100 milliseconds), rod block setpoints (RBS) are (.alculated for OLMCP monitoring (48 values) and for OMU1GR monitoring (48 x 4 values). Then the calculated setpoints are compared with the real time averaged LPRM readings for each region / segment. The ATM issues a trip signal if any regionally averaged LFRM reading exceeds the calculated RBS. This trip s'.gnal causes a rod block within RC&IS and also a flow change block in the Reirculation Flow Control System (RFCS).

Provided below is a summary description of OMCPR and OMMCR RBS calculation methodology.

(a) OMCPR PBS Calculation Methodology. The 16 fuel bundles of each region are surrounded by four LPRM strings. There are four LPRMs in each string. For regional OLMCPR monitoring, the sum of the average of each Ir. vel of B, C, and D of the four LPRM strings is used. The formula f 3r calculating the OMCPR RBS is:

LPRMg*A o* RMCPRt RBS g - -

(1)

OLMCPR where:

RBS o Operating limit rod block setpoint.

LPRMt

Initial sum of average of four LPRMs of B, C, and D levels that surround each region.

Ao . Margin factor for operating limit rod block; a known function of rod pull distan<e.

RMCPR t  : Regional initial MCPR, i.e., the minimum CPR of the 16 bundles in the region spanned by the four LPRM strings. Rnown input from predictor (process computer).

OLMCPR  : Operating limit MCPR in the current cycle; a known function of power.

.l.

I N S G ft h A CQNTlHU6D Formula (1) is applicable to cases where there is no core flow enange end when only one control rod is moved. Adjustmentss are made to the calculated RBS o to account for changes in core flow and adjacent control rods movements.

(b) OLML4CR RBS Calculation Methndolony. The formula for calculating the OLMuiGR RBS is:

LPMi (X)

• B m *M p MAPRATi (X) where:

RSS,(X)  : Calculated operating limit warimum average planar l linear heat generation rate (OLMAPUICR) RBS at LPRM level X.

LPMt (X): Initial avarage of the four LPRMs (level X) at the four corners of each 16 bundle fuel region. The region monitored by the X level LPRM is the region covered up to 1.5 feet above and below the LPM (3 feet total).

B(X)  : Margin factor for MAPuiCR operating limit rod block for X level LPRMs. A knoen function of power and rod position.

Kp  : Off rated power factor to consider overpower condition during worst transient at off-rated condition. A known function of power.

MAPRATi (X):

Regional initial maximum MAPRAT for level X, i.e., the maximum MAPRAT of the 16 bundles within the 3 feet section covt. red by the X level LPRMs. A kneen input from thu 3D monitor.

! In formulas (1) and (2) above, " initial" refers to values that are l

downloaded from the "3D Predictor Monitor" subsystem of the plant Performance Monitoring & Control System (PMCS). A download is requested by ATLM whenever changes in reactor power and/or cose flow exceed a preset limit. A download i can also be manuclly requested by the operator, l

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