ML20134N294

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Rev 00 to Functional Design Requirement for Control Element Assembly Calculator
ML20134N294
Person / Time
Site: Palo Verde, Arkansas Nuclear, Waterford, San Onofre, 05000000
Issue date: 07/31/1985
From:
ABB COMBUSTION ENGINEERING NUCLEAR FUEL (FORMERLY
To:
Shared Package
ML19269B632 List:
References
CEN-304-NP, CEN-304-NP-R, CEN-304-NP-R00, NUDOCS 8509050082
Download: ML20134N294 (80)
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Text

O FUNCTIONAL DESIGN REOUIREMENT FOR A CONTROL ELEMENT ASSEMBLY CALCULATOR CEN-304-NP Nuclear Power Systems COMBUSTION ENGINEERING, INC.

Windsor, Connecticut O

July, 1985 O

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LEGAL NOTICE This report was prepared as an account of work sponsored by Combustion Engineering, Inc. Neither Combustion Engineering, nor any person acting on its behalf:

a. Makes any warranty or representation, express or implied including the warranties of fitness for a particular purpose or merchantability, with respect to the accuracy, completeness, or usefulness of the information contained in this Q report, or that the use of any information, apparatus, method, or process disclosed in this report may not infringe privately owned rights; or
b. Assumes any liabilities with respect to the use of, or for damages resulting from the use of,-any information, apparatus, method or process disclosed in this report.

O CEAC Func. Design Requirements CEN-304 Revision 00 Page II

ABSTRACT

[]

This document provides a description of the CEA Calculator (CEAC) and CEA Penalty Factor Algorithm functional design to be implemented in the Core Protection Calculator (CPC) System of the Reactor Protection System. The scope of this functional description includes detailed specification of the CEAC Penalty Factor Algorithm, which is a component of the CPC/CEAC software.

Two CEACs are provided in the Core Protection Calculator System. Each CEAC receives all of the CEA positions and calculates two penalty factors based on the severity of CEA deviation within a subgroup. These two penalty factors are transmitted to the CPCs to be included in the DNBR and LPD calculations. Detailed algorithm descriptions are provided.

The algorithm equations are written in symbolic algebra. All variables are defined, and units are specified where applicable. In addition, the 16-bit output buffer, which transmits the penalty factors to the CPCs, is defined.

O CEAC Func. Design Requirements CEN-304 Revision 00 Page III

p TABLE OF CONTENTS O

'Section No. Title Page No.

ABSTRACT III TABLE OF CONTENTS IV LIST OF FIGURES, TABLES AND APPENDICES VI i

LIST OF ACRONYMS AND DEFINITIONS VII

1.0 INTRODUCTION

1-1 1.1 PURPOSE 1-1 1.2 SCOPE 1-1 1.3 APPLICABILITY 1-2 1.4 REQUIRED REFERENCES 1-2 2.0 CEAC DESIGN BASIS 2-1 2.1 SPECIFIED FUEL DESIGN LIMITS 2-1 2.2 ANTICIPATED OPERATIONAL OCCURRENCES (A00's) 2-1 3.0 FUNCTIONAL DESIGN AND COMPUTER DESIGN REQUIREMENTS 3-1 3.1 CEA CALCULATOR PENALTY FACTOR ALGORITHM FUNCTIONAL REQUIREMENT 3-1 3.1.1 Requirements for Accommodation of Defined Sing 1' 3-2 CEA-Related A00's 3.1.2 Inputs and Outputs 3-2 3.2 PROGRAM STRUCTURE 3-4 3.3 PROGRAM TIMING AND INPUT SAMPLING RATES 3-7 3.4 PROGRAM INTERFACES 3-8 3.4.1 CEAC Failure Flag 3-9 3.4.2 Case 2 Deviation Flag 3-10 3.4.3 Reactor Power Cutback Flag 3-10 3.4.4 Scaling Flag 3-11 3.4.5 CEAC Off-Line Storage and Reloading 3-12 O

CEAC Func. Design Requirements CEN-304 Revision 00 Page IV i

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l TABLE OF CONTENTS (Cont'd.)

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Section No. Title Page No.

3.5 OPERATOR INTERFACE 3-12 3.5.1 Alarms and Annunciators 3-12 3.5.2 Displays and Indicators 3-13 3.5.3 Operator Input 3-16 3.6 INITIALIZATION 3-18

, 3.7 TESTING REQUIREMENTS 3-18 4.0 ALGORITHM DESCRIPTION 4-1 4.1 PENALTY FACTOR ALGORITHM 4-2 4.1.1 Algorithm Input 4-2 4.1.1.1 Determination of Reactor Power Cutback 4-8 4.1.2 Determination of Deviation 4-14 4.1.3 Determination of Penalty Factors 4-25

/~') 4.1.4 Packing of Penalty Factors for Transmittal to CPCs 4-35

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4.1.5 CEAC Initialization 4-38 4.1.6 CEAC Constants 4-39 L

O CEAC Func. Design Requirements CEN-304 Revision 00 Page V

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LIST OF TABLES Table No. Title Page No.

3-1 CEAC OUTPUT SIGNALS 3-5 3-2 EXAMPLE OF FAILED SENSOR ARRAYS 3-15 3-3 ADDRESSABLE CONSTANTS 3-17 4-1 ASSIGNMENT OF CEDMs TO SUBGROUPS 4-3 4-2 ASSIGNMENTS OF SUBGROUPS TO CONTROL GROUPS FOR 4-4 i

LIST OF FIGURES Figure No. Title Page No.

3-1 CEA CALCULATOR INPUT INTERFACE DIAGRAM 3-3 4-1 PENALTY FACTOR COMPONENTS 4-31 LIST OF APPENDICES Appendix Title Page No.

A SYSTEM 80 PLANTS A1 - A8 O

CEAC Func. Design Requirements CEN-304 Revision 00 Page VI

LIST OF ACRONYMS AND DEFINITIONS Name Definition ANO-2 ARKANSAS NUCLEAR ONE - UNIT 2 A00 ANTICIPATED OPERATIONAL OCCURRENCE CEA CONTROL ELEMENT ASSEMBLY CEAC CONTROL ELEMENT ASSEMBLY CALCULATOR CEDM CONTROL ELEMENT DRIVE MECHANISM CPC CORE PROTECTION CALCULATOR CRT CATHODE RAY TUBE DISPLAY UNIT DNBR DEPARTURE FROM NUCLEATE BOILING RATIO LPD LOCAL POWER DENSITY SONGS-2,3 SAN ONOFRE NUCLEAR GENERATING STATION - UNITS 2, 3 WSES-3 WATERFORD STEAM AND ELECTRIC STATION - UNIT 3 PVNGS-1,2,3 PALO VERDE NUCLEAR GENERATING STATION - UNITS 1, 2, 3 MAX (---) MAXIMUM VALUE OF THE FOLLOWING MIN (---) MINIMUM VALUE OF THE FOLLOWING RPC REACTOR POWER CUTBACK RSPT REED SWITCH POSITION TRANSMITTER SAFDL SPECIFIED ACCEPTABLE FUEL DESIGN LIMITS CEAC Func. Design Requirements CEN-304 Revision 00 Page VII

1.0 INTRODUCTION

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1.1 PURPOSE e - ,

The purpose of i;his do'cument is to provide a description of the latest approved CEA Calculator (CEAC) functional design. This document incorphrates all the approved modifications made to CEN-148(S) (Reference 1.4.1) as documented in References 1.4.2*thru 1.4.4 and as approved in References 1.4.5 thru 1.4.9. This d&ument is for NRC information only as it contains information that has already been reviewed and approved by the NRC Staff. This document will serve as the base reference for fut6re modifications and is intended to be updated as future modifications are approved and implemented.

1.2 CCOPE This Functional Design Requirement provides the following:

C 1. The CEA Penalty Factor Algorithm to be implemented in the Core Protection Calculator System of the Reactor Protection System,

2. Algorithms to initiate alarms for CEA sensor failure and CEA '

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3. A diagnostic failed sensor data l stack,
4. RequirementsonCEAC/CPCinterfaces,systemint[rfaces,and j 7 system initializatien. .

The Functional Design Requirements described in this document when implemented with appropriate data base constants meet the design bases for CEAC given in Section 2.0.

For System 80 plants'the operator interfaces are contained in Q Appendix A. This includes alarms, annunciators, displays, indicator and the assignment of CEAC's.and subgroups. ,

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CEAC Func. Design Requirements CEN-304 Revisio'n '00l Page 1-1

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1.3 APPLICABILITY This document is a generic description of the CEAC functional design requirements. It is currently applicable to SONGS 2 (Cycle 2) and ANO-2 (Cycle 5). It is intended to be applicable to SONGS 3, WSES-3, and PVNGS-1, 2, and 3 when this version of the Functional 4

Design Requirements is implemented and/or referenced at these plants.

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1.4 REQUIRED REFERENCES 1

1.4.1 Functipnal Design Specification for a Control Element Assembly Calcufator,CEN-148(S)-NP, January 1981.

v 1.4.2 CPC/CEAC Software Modification for Waterford 3, CEN-197(C)-NP, March

, 1982.

1.4.3 CPC/CEAC Software Modifications for System 80, LD-82-039, Enclosure J, 1-NP, March 1982.

l'.4.4 CPC/CEAC Software Modification for San Onofre Nuclear Generating Station Units No. ? and 3, CEN-281(S)-NP, July 1984.

1.4.5 ' Safety Evaluation Report Related to Operation of San Onofre Nuclear Generating Station, Unit 2 and 3, Docket Nos. 50-361 and 50-362, f

! Southern California Edison Company, January 1982.

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l 1.4.6 Safety Evaluation Report Related to the Operation of Waterford Steam Electric Station Unit N0. 3, Docket No. 50-382, Louisiana Power and Light Company, July 1981.

  • t l',4,. 7 S'afety Evaluation Report Related to the Operation of Palo Verde Nuclear Generating Station, Units 1, 2 and 3, Docket Nos.

J's '

u Stn ,50-528, Stn 50-529, and Stn 50-530, Arizona Public Service j ': Company, October 1984, i

CEAC Func. Design Requirerents CEN-304 Revision 00 Page 1-2

I 1.4.8 Safety Evaluation Related to Amendment No. 32 to NPF-10 and  ;

Amendment No. 21 to NPF-15 for San Onofre Nuclear Generating Station, Units 2 and 3, Docket Nos. 5-361 and 50-362, Southern California Edison Company, March 1985.

I 1.4.9. Safety Evaluation Related to Amendment No. 66 to Facility Operating License No. NPF-6, Arkansas Power & Light Company, Arkansas Nuclear One Unit 2, Docket No. 50-368, May 1985.

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CEAC Func. Design Requirements CEN-304 Revision 00 Page 1-3

2.0 CEAC DESIGN BASIS The function of the CEAC is to scan all CEA positions and, based on any single-CEA deviation detected within a CEA subgroup, to calculate the single CEA position-related penalty factors necessary to ensure that the CPCs calculate conservative approximations to the actual core peak Local Power Density (LPD) and Departure from Nucleate Boiling Ratio (DNBR) during single CEA-related Anticipated Operational Occurrences (A00s). The CEAC must also be capable of detecting a reactor power cutback event.

2.1 SPECIFIED FUEL DESIGN LIMITS The fuel design limits used to define the low DNBR and LPD trip settings in the CPC to ensure the following Specified Acceptable Fuel Design Limits (SAFDLs) are not exceeded are:

a. The DNBR in the limiting coolant channel in the core shall not be less than the ratio where there is at least a 95%

probability, with 95% confidence, that DNB is avoided.

b. The peak LPD in the limiting fuel pin in the core shall not be greater than that value corresponding to the minimum temperature which would initiate centerline fuel melting.

2.2 ANTICIPATED OPERATIONAL OCCURRENCES (A00s)

. Anticipated operational occurrences are defined in Appendix A of 10CFR50 (General Design Criteria for Nuclear Power Plants) as:

. . . those conditions of normal operation which are expected to occur one or more times during the life of the nuclear power unit .

The A00s accommodated by the CPCs using the CEAC-generated penalty k factors are the insertion or withdrawal of a single full-length or part-length CEA including:

CEAC Func. Design Requirements CEN-304 Revision 00 Page 2-1

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A. Uncontrolled insertion or withdrawal of a single CEA; B. A single dropped full or part-length CEA; C. A single CEA sticking, with the remainder of the CEAs in that subgroup moving;

, D. A statically misaligned full or part-length CEA.

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i CEAC Func. Design Requirements CEN-304 Revision 00 Page 2-2

3.0 FUNCTIONAL DESIGN AND COMPUTER DESIGN RE0VIREMENTS 3.1 CEA CALCULATOR PENALTY FACTOR ALGORITHM FUNCTIONAL REQUIREMENT The CPC determination of the planar radial peaking factors at any given axial node is done by a table look-up routine (Reference 1.4.1). This table look-up routine utfifzes a precalculated table of values for the planar radial peaking factor associated with those CEA groups that are inserted or withdrawn in a normal sequence into the axial node of interest. The normal sequence of group insertion or withdrawal is the prescribed plant technical specification sequence. To account for the increased radial peaking that would result from conditions other than normal, CEA position-related penalty factors are then applied. These penalty factors are multiplicative factors applied to the look-up value to increase the planar radials for the effects of CEA groups being inserted or withdrawn out of normal sequence and for excessive misalignment of subgroups from the group position. The penalty factors associated with the CEA group and subgroup A00s are calculated by the CPCs.

The CEA Calculator (CEAC) accomodates the single CEA deviation-related A00s.

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The single CEA deviation penalty factors calculated by the CEAC will accommodate changes in the LPD and DNBR. The DNBR and LPD penalty factors calculated in the CEACs accommodate changes in the core axial, radial shapes and the core power not perceived in the CPCs during single CEA deviation events.

The single CEA deviation penalty factors calculated by the CEAC must be such that a conservative approximation of the peak local power density and minimum DNBR is obtained in the CPCs during individual CEA-related A00s. To satisfy this requirement the following specific functional requirements, as a minimum, must be satisfied.

O CEAC Func. Design Requirements CEN-304 Revision 00 Page 3-1

q 3.1.1 Requirements for Accomodation of Defined Single CEA-Related A00s V

The CEA deviation Penalty Factors generated by the CEAC for use in the CPC trip functions must be designed to accommodate the individual CEA-related A00s described in Section 2.2. The bases for this requirement are:

1. Criteria 25 and 29 of 10CFR50 Appendix A, " General Design Criteria for Nuclear Power Plants."
2. Regulatory Guide 1.70.

3.1.2 Inputs and Outputs The CEACs shall each receive analog core axial CEA position measurement signals which originate from one of two Reed Switch Position Transmitters (RSPTs) associated with each CEA. Each CEA g position is measured by two redundant independent RSPTs which V transmit analog signals to two redundant independent CEACs (refer to Figure 3-1 for ANO-2). The resolution requirements on the CEAC measurement of CEA position shall be such that (excluding process signal error) CEA position shall be determined to within 0.5%.

The RSPT consists of a series of magnetically actuated reed switches spaced at intervals along the RSPT assembly and wired with precision resistors in a voltage divider network. The RSPT is affixed adjacent to the Control Element Drive Mechanism (CEDM) pressure housing and CEA extension shaft. A magnet attached to the CEA extension shaft actuates the adjacent reed switches, causing a voltage signal proportional to the CEA position to be transmitted for each CEA. The two RSPTs are isolated both electrically and physically from each other. The CEAC input signal derived from the RSPT output has a range of 5 to 10 volts corresponding to 0 to 150 inches of CEA travel, or 0% to 100% withdrawal.

(3 m.)

CEAC Func. Design Requirements CEN-304 Revision 00 Page 3-2

FIGURE 3-1 O -

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CEAC Func. Design Requirements CEN-304 Revision 00 Page 3-3 l

4 The CEAC shall calculate the CEA deviation Penalty Factors based on

' CEA position sensor input data obtained from each of the RSPTs (refer to Figure 3-1 for ANO-2). The components of the CEA deviation Penalty Factors are determined from the following data:

1. Two static penalty factor components calculated as functions of deviation magnitude within a subgroup; one each for DNBR and LPD.
2. A dynamic Xenon penalty factor component calculated as a function of elapsed time during which excess deviation exists in the subgroup.

3._ Two correction constants for the Xenon component; one each for DNBR and LPD.

The output signals for each CEAC are listed in Table 3-1.

The two contact outputs must actuate operator alarms. The six i digital-word outputs form the 16-bit output buffer which transmits the CEA penalty factors to the CPCs. The CEAC Failure Flag indicates the quantity of failed sensors or the quantity of deviating CEAs per core quadrant exceed limiting pre-set numbers.

Actuation of the CEA Failure Flag is described in more detail .in Section 3.4.1. The Scale Flag indicates the range of the penalty I

factors, and is described in more detail in Section 3.4.3.

3.2 PROGRAM STRUCTURE i

The CEAC design bases require that the calculator be capable of detecting a reactor power cutback event, detecting CEA deviation, l calculating the single CEA deviation penalty factors, and indicating I by alarm and indicator flag CEA deviation, CEAC failure, and sensor out-cf-range failures. In addition, the CEAC will provide l .

diagnostic information on CEA sensor failures. Therefore, the CEAC

Penalty Factor Algorithm has been designed

i CEAC Func. Design Requirements CEN-304 Revision 00 Page 3-4

Table 3-1 CEAC Output Signals Signal Type Range CEAC Failure Flag Digital Word 1 Packed DNBR Penalty Factor Digital Word I (minus 1.0)

Multiple CEA Deviations Digital Word 1 in Subgroup Flag Reactor Power Cutback Flag Digital Word i Packed LPD Penalty Factor Digital Word 1 (minus 1.0)

Scale Flag Digital Word 1 Sensor out-of-range Contact Output l Alarm  !

l CEA Deviation Alarm Contact Output l l

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1. Part of 16-bit output buffer.
2. See Section 3.4.

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CEAC Func. Design Requirements CEN-304 Revision 00 Page 3-5 l

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,o 1. To recognize the initiation of a reactor power cutback event.

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2. To calculate the deviation (difference in position) amongst the CEAs in each subgroup.
3. To recognize excessive CEA deviation within a subgroup, and to identify each occurrence as a single CEA withdrawal, single CEA insertion, or multiple CEA deviations within a subgroup.
4. To calculate and/or look up a penalty factor for LPD, and a penalty factor for DNBR based on the type of deviation event, the magnitude of the deviation, the CEA subgroup with the deviation, the CEA configuration, and the elapsed time since the start of the deviation. The LPD and DNBR penalty factors shall be selected as the maximum of the LPD and DNBR penalty factors calculated for each subgroup. The maximum penalty factors minus one will be transmitted to the CPCs as part of the output of the CEAC.
5. To determine the status of the CEAC sensor fail alarm and the CEA deviation alarm.
6. To check some conditions under which CEAC (or upstream hardware) failure should be indicated to the CPCs.
7. To provide diagnostic information on CEA sensor failures, and on the causes of a CEAC penalty factor.
8. To provide an indicator to the CPCs of the scale used in determining the penalty factors transmitted.
9. To support CEA CRT display software by calculating parameters used for the display.

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CEAC Func. Design Requirements CEN-304 Revision 00 Page 3-6 4

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r) 3.3 PROGRAM TIMING AND INPUT SAMPLING RATES U

The CEAC Penalty Factor Algorithm software is designed for the purpose of providing, for existing CEA configurations, an on-line real-time determination of the single CEA deviation DNBR and LPD penalty factors to be applied in the CPC determination of the hot pin heat flux distribution, the adjusted compensated core average power, and the local power density. The algorithm required for this purpose is time oriented, with a calculation scheduling rate and update period that is compatible with overall CEAC/CPC system response requirements. The execution period is the maximum time in seconds from the time CEA RSPT sensors are scanned to the time the CEAC calculated outputs are updated with new information from that input scan and calculation. The calculations shall be scheduled in such a manner that the update requirements are met.

There are two CEAC System update periods:

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1. The Update Period The update period consists of a periodic fixed

{Program

] algorithm scheduling rate. The CEAC Penalty Factor outputs shall be updated every

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2. The Update Period (See Appendix A for SYS 80)

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This update consists of a fixed algorithm scheduling rate with

. The CEAC Penalty Factor Program calculated output to a CRT bar graph display showing individual CEA positions arranged in subgroups and groups shall be updated at least every{ .

The tolerance on the execution periods is .

O CEAC Func. Design Requirements CEN-304 Revision 00 Page 3-7

3.4 PROGRAM INTERFACES Communications with the CPCs must be rapid and simple. In addition, the output to the CPCs must not change until after execution of the CEACs has been completed. This is accomplished by a 16-bit output buffer which transmits data to each CPC. This output buffer shall have a memory location, and the 16 bits shall be assigned in the following manner:

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O CEAC Func. Design Requirements CEN-304 Revision 00 Page 3-8

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3.4.1 CEAC Failure Flag A CEAC failure flag shall be transmitted to the CPCs as part of the 16-bit output buffer. This flag shall be set true when either or both of the following conditions occur: ,,,, ,

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The CEAC Penalty Factor Program shall perform sensor out-of-range validity checks on the raw RSPT sensor input data and initiate a sensor-cut-of-range alarm when out of range conditions are detected.

Analog signals outside the acceptable operating range represent failure of the RSPT. If this check indicates sensor in-range, a

)isthenperformed. If either of these checks fail, the sensor fail flag is set.

O CEAC Func. Design Requirements CEN-304 Revision 00 Page 3-9

-O In addition, the CEAC failure flag shall set for internal processor faults including fixed point divide faults, floating point arithmetic fault, memory parity errors, illegal machine instruction, or failure to meet the timing requirements of Section 3.3.

3.4.2 Case 2 Deviation Flag A Case 2 deviation (or large penalty factor) flag shall be trans-mitted to the CPCs as part of the 16-bit output buffer. This flag shall be set true when either or both of the following conditions occur: .

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The CEAC Penalty Factor Program shall check for indications of 3.4.3 Reactor Power Cutback Flag A Reactor Power Cutback (RPC) Flag shall be transmitted to the CPCs as part of the 16-bit output buffer. This flag shall be set (IRPC=1) when the following conditions occur:

O CEAC Func. Design Requirements CEN-304 Revision 00 Page 3-10

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- 1 3.4.4 Scaling Flag j l

After the DNBR and LPD penalty factors have been calculated, each ,

penalty factor is prepared for packing into the 16-bit output buffer

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O CEAC Func. Design Requirements CEN-304 Revision 00 Page 3-11

- 3.4.5 CEAC Off-Line Storage and Reloading To accommodate events where reloading of the CEAC Penalty Factor Algorithm program is required because of software and/or hardware failures, a means shall be provided to permit rapid reloading of the CEAC software from a suitable off-line mass storage device (one per CEAC). The off-line storage device shall be utilized for normal CEAC start-up loading but not during normal CEAC operation.

3.5 OPERATOR INTERFACE The reactor operator shall be informed of the status of the CEACs by threemechanisms(forSys80SeeAppendixA).

1. The calculators generate alarms to alert the operator to CEA sensor failure or excessive CEA deviation.

O L' 2. The CRT Video Monitor displays the position of the individual CEAs arranged into subgroups and control groups utilizing a bar graph representation, the floating point vdlues of the two penalty factors, and a flag to indicate the cause of any alarms.

3. The CPC/CEAC operator's module provides CEAC inputs, selected intermediate variables, and outputs.

3.5.1 Alarms and Annunciators A CEA deviation alarm (including Case 2 type deviations) and a failed sensor alarm shall be provided to the Plant Annunciator System (audible and visual) and to the CPC/CEAC operator's module.

Removal of the alarm indication should be prohibited unless the condition causing the alarm no longer exists.

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CEAC Func. Design Requirements CEN-304 Revision 00 Page 3-12

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-L) 3.5.2 Displays and Indicators Both CEACs shall be linked to a single CRT Display Generator for the purposes of displaying individual CEA position information. The connection between the data link and each individual CEAC shall be made via an appropriate isolation device (as defined in IEEE Std. 279-1971). A manual selection switch shall be' utilized to determine which of the two CEACs the Display Generator will utilize in generating a CEA position display. The CEA Position Display (Figure 3-1) consists of a CRT Video Monitor and a Display Generator. For System 80 see Appendix A.

The CRT Video Monitor shall display the position of the individual CEAs arranged into subgroups by control groups utilizing a bar graph representation. The CEAs and subgroups assigned to each control group shall be recorded above the bar graphs. The CRT shall provide an indication of CEA deviation which allows the deviating CEAs to be

,q identified as well as the magnitude of the deviation.

V Provisions shall also be made to allow the operator to obtain a digital position read out in units of inches from the bottom of the core by addressing the particular point I.D. of the CEA on the operator's module. Certain CEAC intermediate variables and outputs (including the LPD and DN8R penalty factors and the packed penalty faitor word to be transmitted to the CPCs) shall be available l through the operator's module.

Each CEAC shall provide diagnostic information to the operator via l

l the operator's module or a teletype. The three types of diagnostic information to be provided are:

1. Failed sensor stack.

CEAC Func. Design Requirements CEN-304 Revision 00 Page 3-13

2. A " snapshot" or listing of CEA positions, penalty factors, and time of occurrence of the deviation.
3. A flag indicating the cause of any alarm.

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Each CEAC performs sensor input out-of-range checks ,

_ ] This information can be retrieved through the operator's module or a teletype. The failed sensor stack should be saved through auto-restarts.

A " snapshot" of CEA positions, penalty factors, and time of deviation occurrence is initiated by 1) a CEAC penalty factor

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greaterthanone,2)thelargePFflag,3)aCEACfailur(

O CEAC Func. Design Requirements CEN-304 Revision 00 Page 3-14

i Table 3-2 Q

Example of Failed Sensor Arrays I

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O CEAC Func. Design Requirements CEN-304 Revis1on 00 Page 3-15

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_ ].Thisinformationcanberetrievedthrougha teletype. The CEAC snapshot should be saved through auto-restarts.

A CEAC fail indication is transmitted to the CPCs under the following conditions:

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3. Initialization and in-test mode,
4. CEAC hardware failure,
5. CEAC memory unprotected, p

V 6. Watchdog timer timeout.

3.5.3 Operator Input The operator must have the capability to change a limited set of program constants, called addressable constants, via the input /

output device. Modification of addressable constants shall be permitted only when a manual interlock has been activated. In addition means shall be provided to prevent modification of any constants not designated " addressable". The required addressable constants are limited to one constant for clearing the snapshot buffer (3.5.2) and one constant for the Reactor Power Cutback maximum time limit. A method shall also be provided to permit rewriting the entire CRT display on command. The required addressable constants are listed in Table 3-3.

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CEAC Func. Design Requirements CEN-304 Revision 00 Page 3-16

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i Table 3-3

Addressable Constants Symbol Definition Range BUFTRP Snapshot Buffer Control Flag TC8P Maximum time that the RPC Flag Can Remain Set (Seconds) _

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CEAC Func. Design Requirements CEN-304 Revision 00 Page 3-17

3.6 INITIALIZATION The CEACs must be capable of initia11 zing to steady state operation for any allowable plant operating condition. Initialization should be complete within f initial CEAC startup or of restart following a CEAC failure or in-test condition. Until initialization of a CEAC is complete, the CEAC failure flag shall be set.

During initialization, the calculated penalty factors shall approach the steady state value from the conservative direction.

Initialization shall be considered to be complete after at least executions of the CEAC initialization program have occurred.

3.7 TESTING REQUIREMENTS The CEAC shall be designed to perform periodic testing of the CEAC Penalty Factor Program upon operator demand.

O The bases for this requirement are:

1. IEEE Std. 338-1971, "IEEE Trial Use Criteria for the Periodic Testing of Nuclear Power Generating Station Protection Systems."
2. Criteria 21 and 22 of 10CFR50 Appendix A," General Design Criteria for Nuclear Power Plants."
3. Regulatory Guide 1.22, " Periodic Testing of Protection System Actuation Functions."

The testing of the system shall be accomplished by disabling the input interface and simulating new inputs from a periodic testing data base. Selected outputs will then be checked against a corresponding expected value data base, and differences will be n identified. During the time the CEAC is performing the periodic test a digital code shall be generated and transmitted to the CPCs to identify that the CEAC unit is in-test.

CEAC Func. Design Requirements CEN-304 Revision 00 Page 3-18

p 4.0 ALGORITHM DESCRI.oTION LJ This section includes a detailed description of the functions to be performed by the CEAC Program. For the program described below, the sequence of computations required is described in sufficient detail to allow the software designer to specify the coding of the protection program.

The penalty factor algorithm produces two penalty factors, one for DNBR and one for LPD. These penalty factors are found by taking the largest DNBR penalty factor and the largest LPD penalty factor calculated for any subgroup. The penalty factors on the subgroup level are formed by combining a static DNBR penalty factor component with a dynamic Xenon penalty factor component, and by combining a static LPD penalty factor component with a dynamic Xenon penalty factor component.

p The static DNBR and static LPD penalty factor components are

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. The dy ic Xenon penalty factor component is calculated a]s a

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of CEA position signals are read in and processed to screen out false signals, and the status of the sensor fail alarm is determined.

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CEAC Func. Design Requirements CEN-304 Revision 00 Page 4-1

O 4.1 PENALTY FACTOR ALGORITHM 4.1.1 Algorithm Input The inputs to the algorithm are a set of live CEA position signals received from the reed switch position transmitters. Each signal is processed to screen out false signals, i.e. each signal is checked .,

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CEAC Func. Design Requirements CEN-304 Revision 00 Page 4-2

TABLE 4 _1

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v Assignment of CEDMs to Subgroups for ANO-2**

Sub-Group No. CEDM No.

1 2,3,4,5 2 6,7,8,9 3 10, 11, 12, 13 4 14, 16, 18, 20 5 15, 17, 19, 21 6 22, 23, 24, 25 7 26, 27, 28, 29 8 30, 32, 34, 36 9 31, 33, 35, 37 10 38, 40, 42, 44 11 39, 41, 43, 45

,n 12 46, 47, 48, 49 13 50, 52, 54, 56 14 51, 53, 55, 57 15 58, 59, 60, 61 16 62, 64, 66, 68 17 63, 65, 67, 69 18 70, 73, 76, 79 19 71, 74, 77, 80 20 72, 75, 78, 81

  • xx *1
1. *CEDM No.1 is to be capable of being assigned to any one of the 20 subgroups.
2. The assignment of CEDMs to subgroups as controlled by the CEDMCS is fixed for the life of the plant (except for CEDM #1)
3. For AP&L, CEDM No.1 is assigned to subgroup No.12.

O ** This CEDM assignment will differ for other plants.

CEAC Func. Design Requirements CEN-304 Revision 00 Page 4-3

I p TABLE 4-2 v

Assignments of Subgroups to Control Groups for ANO-2**

ASSIGNMENT OF SUBGROUPS TO CONTROL GROUPS CONTROL GROUPS * (Subgroup No.)

Regulating Group #6 12 Regulating Group #5 15 Regulating Group #4 3 Regulating Group #3 16, 17 Regulating Group #2 2, 19 Regulating Group #1 10, 11 Shutdown Group A 13, 14, 18, 20 Shutdown Group B 1,4,5,8,9 Part-Length Group

{J P1 P2 6

7 Notes:

  • For ANO-2 Regulating Control Group #6 is the first to be inserted in-sequence and Group #1 is the last. Regulating Control Group #1 is the first to be withdrawn in-sequence and Group #6 is the last. The insertion / withdrawal sequence maintains 40% overlap of adjacent groups.
    • This subgroup assignment will vary according to plant.

O CEAC Func. Design Requirements CEN-304 Revision 00 Page 4-4

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APPENDIX A CONFIGURATION FOR SYSTEM 80 PLANTS O

l CEAC Func. Design Requirements CEN-304 Revision 00 Page Al i

p 3.3 PROGRAM TIMING AND INPUT SAMPLING RATES U

The CEAC Penalty Factor Algorithm software is designed for the purpose of providing, for existing CEA configurations, an on-line real-time determination of the single CEA deviation related DNBR and LPD penalty factors to be applied in the CPC determination of the hot pin heat flux distribution, the adjusted compensated core average power, and the local power density. The algorithm required for this purpose is time oriented, with a calculation scheduling rate and update period that is compatible with overall CEAC/CPC system response requirements. The execution period is the maximum time in seconds from the time CEA RSPT sensors are scanned to the time the CEAC calculated outputs are updated with new information from that input scan and calculation. The calculations shall be scheduled in such a manner that the update requirements are met.

There are two CEAC System update periods:

A U 1. The Update Period The update period consists of a periodic fixed Igorithm scheduling rate. The CEAC PenaTty Factor Program outputs shall be updated every .

2. The Update Period This update consists of a fixed algorithm scheduling rate with

] The CEAC Penalty Factor Program calculated output to a CRT bar graph display showing individual CEA positions arran ed in subgroups and groups shall be updated at least every

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The tolerance on the execution periods is .

o CEAC Func. Design Requirements CEN-304 Revision 00 Page A2

(one per CEAC). The off-line storage device shall be utilized for

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normal CEAC start-up loading but not during normal.CEAC operation.

3.5 OPERATOR INTERFACE The reactor operator shall be informed of the status of the CEACs by three mechanisms:

1. The calculators generate alarms to alert the operator to CEA sensor failure or excessive CEA deviation.
2. The CRT Video Monitor displays the position of the individual CEAs arranged into subgroups and control groups utilizing a bar graph representation. If a CEA deviation exists, the group and subgroup having the deviation, the CEAs assigned to the subgroup with the deviation, and the position for each of these CEAs in inches from the bottom of the core will be displayed below the bar graph representation. This display of CEA

'- deviation information is ordered by decreasing penalty factor magnitude and is limited to the information associated with three CEA deviations. In addition CEA sensor failure information (CEA number and type of failure) shall be dis-played, if not preempted by CEA deviation information.

3. The CPC/CEAC operator's module provides CEAC inputs, selected intermediate variables, and outputs.

3.5.1 Alarms and Annunciators A CEA deviation alarm (including Case 2 type deviations) and a failed sensor alarm shall be provided to the Plant Annunciator System (audible and visual) and to the CPC/CEAC operator's module.

Removal of the alarm indication should be prohibited unless the condition causing the alarm no longer exists.

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CEAC Func. Design Requirements CEN-304 Revision 00 Page A3

3.5.2 Displays ~and Indicators

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Both CEACs shall be linked to a single CRT Display Generator for the purposes of displaying individual CEA position information. The l connection between the data link and each individual CEAC shall be made via an appropriate isolation device (as defined in IEEE Std. I 279-1971). A manual selection switch shall be utilized to determine which of the two CEACs the Display Generator will utilize in generating a CEA position display. The CEA Position Display (Figure 3-1) consists of a CRT Video Monitor and a Display Generator.

The CRT Video Monitor shall display the position of the individual CEAs arranged into subgroups by control groups utilizing a bar graph l representation. If a CEA deviation exists, the CRT shall identify the CEA's assigned to the subgroup with the deviation and shall indicate the position of these CEA's in inches from the bottom of l the core below the bar graph representation. The CRT shall also display failed sensor information.

q'v Provisions shall also be made to allow the operator to obtain a digital position read out in units of inches from the bottom of the core by addressing the particular point I.D. of the CEA on the operator's module. Certain CEAC intermediate variables and outputs (including the LPD'and DNBR penalty factors and the packed penalty factor word to be transmitted to the CPCs) shall be available j through the operator's module.

Each CEAC shall provide diagnostic information to the operator via the operator's module or a teletype. The three types of diagnostic information to be provided are:

1. Failed sensor stack.
2. A " snapshot" or listing of CEA positions, penalty factors, and time of occurrence of the deviation.

CEAC Func. Design Requirements CEN-304 Revision 00 Page A4

3. A flag indicating the cause of any alarm.

Each CEAC performs sensor input out-of-range checks and _

. This information can m be retrieved through the operator's module or a teletype. The O failed sensor stack should be saved through auto-restarts.

A " snapshot" of CEA positions, penalty factors, and time of deviation occurrence is initiated by 1) a CEAC penalty factor greater than one, 2) the large PF flag, 3) a CEAC failure l

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CEAC Func. Design Requirements CEN-304 Revision 00 Page A5

i A CEAC fail indication is transmitted to the CPCs under the following conditions:

1. More than a pre-set number of sensors are indicated failed,
2. More than a pre-set number of subgroups contain excessive deviation (excessive deviations are counted by core quadrant),
3. Initialization and in-test mode,
4. CEAC hardware failure,
5. CEAC memory unprotected,
6. Watchdog timer timeout.

O 3.5.3 Operator Input The operator must have the capability to change a limited set of program constants, called addressable constants, via the input /

output device. Modification of addressable constants shall be permitted only when a manual interlock has been activated. In addition means shall be provided to prevent modification of any constants not designated " addressable". The required addressable constants are limited to one constant for clearing the snapshot buffer (3.5.2) and one constant for the Reactor Power Cutback maximum time limit. A method shall also be provided to permit rewriting the entire CRT display on comand. The required addressable constants are listed in Table 3-3.

O V

CEAC Func. Design Requirements CEN-304 Revision 00 Page A6

m TABLE 4-1 Assignment of CEDMs to Subgroups for System 80 Sub-Group No. CEDM No.

1 2,3,4,5 2 6, 8, 10, 12 3 7, 9, 11, 13 4 14, 15, 16, 17 5 18, 19, 20, 21 6 22, 24, 26, 28 7 23, 25, 27, 29 8 30, 31, 32, 33, 9 34, 36, 38, 40 10 35, 37, 39, 41 11 .

42, 43, 44, 45 12 46, 48, 50, 52 C 13 47, 49, 51, 53 14 54, 57, 60, 63 15 56, 59, 62, 65 16 55, 58, 61, 64 17 66, 68, 70, 72 18 67, 69, 71, 73 19 74, 76, 78, 80 20 75, 77, 79, 81 21 82, 83, 84, 85 22 86, 87, 88, 89 23 90, 92, 94, 96 24 91, 93, 95, 97

  • XX *1
1. *CEDM No. 1 is to be capable of being assigned to any one of the 20 subgroups.
2. The assignment of CEDMs to subgroups as controlled by the CEDMCS n/ is fixed for the life of the plant (except for CEDM #1)
3. For System 80 first fuel cycle, CEDM No.1 is assigned to subgroup #8.
4. Subgroups #23 and #24 omitted in 89 CEA plants.

CEAC Func. Design Requirements CEN-304 Revision 00 Page A7

TABLE 4-2 Assignments of Subgroups to Control Groups for System 80 First Fuel Cycle **

ASSIGNMENT OF SUBGROUPS TO CONTROL GROUPS CONTROL GROUPS * (SubgroupNo.)

Regulating Group #5 4 Regulating Group #4 5, 22 Regulating Group #3 1, 11, 21 Regulating Group #2 17, 18 Regulating Group #1 14, 15 Shutdown Group A 2, 3, 19, 20, 23**, 24**

Shutdown Group B 6, 7, 9, 10, 16 Part-Length Group

. P1 8 P2 12, 13 Notes:

  • Regulating Control Group #5 is the first to be inserted in-sequence and Group #1 is the last. Shutdown Group B is the first Shutdown Group to be inserted in-sequence and Shutdown Group A is the first Shutdown Group to be withdrawn in-sequence. Regulating Control Group
  1. 1 is the first to be withdrawn in-sequence and Group #5 is the last.

The insertion / withdrawal sequence maintains 40% overlap of adjacent groups.

    • 0mitted in 89 CEA plants.

O-CEAC Func. Design Requirements CEN-304 Revision 00 Page A8

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