ML20010C770

Nonproprietary Functional Design Spec for Core Protection Calculator,Response to NRC Questions 221.18 & 221.20.

ML20010C770
Person / Time
Site:	San Onofre
Issue date:	03/31/1981
From:	ABB COMBUSTION ENGINEERING NUCLEAR FUEL (FORMERLY
To:
Shared Package
ML13308B934	List: ML13308B933 ML20010C770 ML20010C772 ML20010C774 ML20010C778 ML20010C782
References
CEN-147(S)-NP, NUDOCS 8108200400
Download: ML20010C770 (204)

Text

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O SAN ONOFRE U* LITS 2 AND 3 .

DOCKETS 50-361 AND 50-362 b

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CEN-147(5)-NP ~

FUNCTIONAL DESIGN SPECIFICATION FOR A "

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CORE PROTECTION CALCULATOR

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RESPONSE TO NRC QUESTIONS 221.18 AND 221.20 ,

MARCH 1.981'.S .

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d 1 r C05EUSTION ENGINEERING, INC.

l NUCLEAP.~POUER SYSTEMS POWER SYSTEMS GROUP WIrlD50R, CONNECTICUT 06095 O

8108200400 810813 .

PDR ADOCK 05000361 -

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LEGAL NOTICE This response was prepared as an account of work .

sponsored by Combustion Engineering, Inc. :leither -

Corbustion Engineering nor any person acting on its ~

behalf: .

a: !!akes any warranty or representation, express -

or implied including the warranties of fitness for a particular purpose or cerchantability, with respect to the accuracy, cocpleteness, or usefulness of the '

information contained in this response, or that the use of any information , apparatus, method, or process dis-closed in this response may not infringe privately owned rights; or. .

'. b. Assumes any liabilities with respect to the O use of, or for demeses resuitins from the use of. eny information, appartus, method or process disclosed in this response. '

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___ _ __ _ _ _ _ PAU*_2. "I 203

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This document describes the functional design of the Core Protection Calculator. Included in this design are changes to current ANO-2 Cycle 1 CPC functional design. These changes are indicated'by vertical bars in the right margins. The pages involved are 11 17, .

25, 26, 34 - 37, 42, 43, 45 - 48, 50, 51, 58, 59, 61 - 66, 71, 80, 87 92 - 97, 100 - 104, 106 - 109, 115 - 117, 121 - 127, 133 - 140, 145, 150 - 199, 201 - 203, A-2, A-4 to A-6.

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Abstract

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This document provides a description of the Core Protection Calculator (CPC) System functional design. The scope of this functional description includes detailed specification of the reactor protection algorithms to be implemented in software and system requirements affecting the executive software and hardware design. The CPC System design bases are also . .

presented.

( System requirements are defined to assure that the hardware /

t software configuration.is compatible with the reactor protection algorithms. Requirements are specified in the -

areas of input / output, protection program interactf-on, operator interface, and initialization.

, Algorithm functional descriptions are provided for the I

protection software. The protection software consists of four distinct programs and a subroutine accessible to any

• of the four programs. Detailed algorithm descriptions are provided for each program and the subroutine. The algorithm equations are written in symbolic algebra. All variables are defined, and units are specified where applicable. To -

complete the algorithm descriptions, the output variables and required constants are listed for each program.

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. l TABLE OF CONTENTS Section No. Title Page No.

1.0 INTRODUCTION

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1.1 PURPOSE

.fo 1.2 SCOPE 10

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1.3 APPLICABILITY . 3.f k

2.0 CPC DESIGN BASIS - 17  !

2.1 SPECIFIED FUEL DESIGN LIMITS #7 2.2 ANTICIPATED OPERATIONAL OCCURRENCES (A00s) J7

2. 3

• POSTULATED ACCIDENTS 20 ,

2.4 ADDITIONAL BASES FOR TRIP SETPOINTS 20 2.4.1 RELATIONSHIP BETWEEN MONITORING AND PROTECTION 20 SYSTEMS 2.4.2 CPC TIMING ,

3.1 3.0 SYSTEM REQUIREMENTS .

M 3.1 INPUTS AND OUTPUTS M 3.2 PROGRAM STRUCTURE 27 3.3 PROGRAM TIMING AND INPUT SAMPLING RATES 3.:f 3.4 PROGRAM INTERFACES 31 3.5 OPERATOR INTERFACE 33 3.5.1 ALARMS AND ANNUNCIATORS 33 3.5.2 DISPLAYS AND INDICATORS 33 3.5.3 39 Q OPERATOR INPUT 3V 3.5.4 FAILED SENSOR STACK Page 5 of 203

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- TABLEOFCONTENTS(Cont'd.)

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Section No. Title Page No. 'j 3.5.5 TRIPPED CPC CHANNEL SNAPSHOT '/0  !:

i 3.6 .INITIAlTIATION 74  !

3.7 INTERLOCKS AND PERMISSIVES W

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. 4.0 ALGORITHM DESCRIPTION 4.1 PRIMARY COOLANT MASS FLOW VI  !

4.1.1 ALGORITHM INPUT #/f 4.1.2 FLOW RESISTANCES- ff  ;

4.1.3 CORE FLOW CALCULATION .

f/ j 4.1.4 FLOW PROJECTION is.  !!

4.1.5 FLOW OUTPUT sf "5'^"'S

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60 ;i 4.2 DNBR AND POWER DENSITY UPDATE ,

4.2.1 INPUT TO UPDATE ,

61 ll 4.2.2 TEMPERATURE COMPENSATION 67 4.2.3 NEUTRON FLUX POWER 71 j t

4.2.4 CEAC PEr(ALTY FACTORS 7A '!

I 4.2.5 HEAT FLUX COMPENSATION Ef, ,i 4.2.6 UPDATE OF DNBR PENALTY FOR ASYMMETRIC STEAM Sf .

GENERATOR TRANSIENTS ,!

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4.2.7 UPDATE OF DNBR AND QUALITY MARGIN . 92 4.2.8 COMPENSATED LOCAL POWER DENSITY ~

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l; 4.2.9 UPDATE OUTPUTS /0/ ii l Ii 4.2.10 UPDATE CONSTANTS /#3 {,j

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t 4.3.1 POWER INPUT ,

Page'6 of 403

1.......

TABLE OF CONTENTS (Cont'd.)

Se'ction No. Title Page No.

4.3 2 SUBGROUP DEVIATION PENALTY FACTOR 11 3 , , i 4.3.3 PLANAR RADIAL PEAKING FACTORS AND CEA //V . .' !

SHADOWING FACTORS .

4.3.4 OUT OF' SEQUENCE CONDITIONS 12 8 i! l 4.3.5.

EXCORE SIGNAL NORMALIZATION /30 il l 1

4.3.6 POWER DISTRIBUTION SY!! THESIS 13d -

l 4.3.7 ASI - DEPENDENT PARAMETERS /YG

.,l 4.3.8 PSEUDO HOT PIN POWER DISTRIBUTION /YS  !

4.3.9 ,

BASE CORE COOLANT MASS FLOW RATE 'lyf I 4.3.10 POWER OUTPUT jff

.j 4.3.11 POWER CONSTANTS 15/ !l O 4.4 STATIC DNBR AND POWER DENSITY /55 .

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4.4.1 INPUTS 155- -

4.4.2 UPGRADE POWER DISTRIBUTION DATA FOR STATIC DNBR CALCULATION ff6 !l j

4.4.3 SATURATION PROPERTIES AND PRES 3URE DEPENDENT /57 j i TERMS l

( . i 4.4.4 CALCULATION OF INLET COOLANT MA$S FLUX AND REGION DEPENDENT PARAMETERS f57 ll ,

I i 4.4.5 CALCULATION OF LINEAR HEAT DISTRIBUTIONS 160 i i

4.4.6 COMPUTATION OF CORE / HOT-ASSEMBLY FLUID 163 il PROPERTIES

, Il 4.4.7 CALCULATION OF BUFFER / HOT-CHANNEL FLUID /20 -

PROPERTIES

-l 4.4.8 COMPUTATION OF HOT CHANNEL QUALITY AND /2'/ '!

FLOW PROFILES i n

U 4.4.9 HOT CHANNEL liEAT FLUX DISTRIBUTIONS /7f ,j Ii

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TABLEOFCONTENTS(Cont'd.)

oL Section fio. Title Page No.- '-

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4.4.10 CORRECTION FACTORS FOR HON-UNIFORM HEATING /7(

4.4.11 CALCULATION OF STATIC DNBR /?7 l 1

4.4.12 STATIC THERtML POWER fil 4.4.13 DEFINITION OF VOLUME FUNCTIONS fif .

i' 4.4.14 DEFINITION OF FRICTION FACTOR FUNCTION /f( ,

1 4.4.15 STATIC OUTPUTS /f.3 .!

1-4.4.16 STATIC CONSTANTS /ff ;I 4.5 TRIP SEQUENCE ALGORITHM /fs i i!

4.5.1 INPUT TO THE TRIP SEQUENCE ALGORITHM /7s 'j 4.5.2 DNBR/ QUALITY TRIP /ff  !

4.5.3 LPD TRIP - -

2 03 .~ l l O 4.5.4 AuxitIARv TRIPS so2 >'

4.5.5 TRIP SEQUENCE CONSTANTS 2 03 LIST OF TABLES !l Table No. Title Page No. il 3-1 CPC Process Input Signals ;ty l'

'3-2 CPC Output Signals R$  !

i 3-3 Program Execution Intervals and Input Sampling 3R !i Rates  ;

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3-4 Addressable Constants 35 -

l 3-5 Failed Sensor ids 39  :

3-6 Variables for CPC Channel Trip Snapshot '/l Correspondence of Index i(= 1, 12) to CEA 4-1 / l 2. .

Groups ,  ;

4-2 . Core Spline Regions /'/4 Page 8 of 203

Q, LIST OF FIGURES Figure No. Title Page No.

3-1 CPC I/O Configuration 2C i 4-1 Schematic of Primary System Showing Vf Approximate Location of Temperature Sensors 4-2 Penalty Components for . if

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4-3 Sample Planar Radial or Shadowing Factor //8 Lookup Table .

4-4 Partition for Application of Addressable l

/2'/ l Multipliers for Planar Radials (oR i) and Rod Shadowing (agg) Factors 4-5 Partition for Application of Den'sity Slope /Jf ~

Table Indices (KDen) at each Axial flode N .

4-6 Plots of

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. O LIST OF APPEf1 DICES Appendix Title - Page No.

A Parameters to be Displayed by CPC I/O De'vice A-1

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1.0 INTRODUCTION

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. 1.1 . PURPOSE

. The purpose of this document is

1) To specify a Core Protection Calculator (CPC) functional design and functional interface that meet the design bases .

given in Section 2.0, when implemented with quality assured data constants, .

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2) To serve as a quality assured design interface document between the C-E engineering groups responsible for specifi-cation of the CPC functional des'ign and those responsible for implementation of the CPC design for the C-E NSSS identified in Section 1.3, and, i

3) To provide a quality assured record of the CPC design for reference by C-E design groups that are not directly responsible for the CPC design, but require knowledge of the design specification for related tasks.

1.2 SCOPE The CPC Design consists of three major components: executive software, application software, and hardware. This functional description provides the following:

1) The reactor protection algorithms to be implemented as the application software and .

2) Requirements on protection program interfaces, system interfaces.  :

protection program timing, and system initialization.

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Items 1) and 2) establish functional requirements affecting the three major CPC components.

1.3 APPLICABILITY This document is a generic description of the CPC functional design. However, applicability is currently limited to Arkansas Nuclear One, Unit 2 and San Onofre Nuclear Generating Station Units 2 and 3. -

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2.0 _Ci'C DESIGN BASIS The low DNBR and high local power density trips, (1) assure that the specified acceptable fuel design limits on departure from nucleate boiling and centerline fuel melting are not exceeded during Anticipated Operational Occurrences (A00), and (2) assist the Eng'neered Safety Features System in limiting the consequences of certain postulated accidents.

2.1 SPECIFIED IUEL DESIGN LIMITS The fuel design limits used to define the subject trip system settings are:

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

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

b. The peak linear heat rate, in the limiting fuel pin in the core, shall not be greater than that value corresponding to f

the centerline fuel melting temperature.

2.2 ANTICIPATED OPERATIONAL OCCURRENCES (A00s)

Anticipated operational occurrences arc defined in Appendix A of 10 CFR 50 (General Design Criteria for Nuclear Power Plants) as:

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

The anticipated operational occurrences that were used to determine the design requirements for the above trip functions are as follows:

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A. Uncontrolled Axial Xenon Oscil1'ations.

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B. Insertion or withdrawal of full-length or part-length CEA ,

groups,U ) including:

1. uncontrolled sequential withdrawal of CEA groups from critical conditions, j

?. . out-of-sequence insertion or withdrawal of a single CEA .

group from critical conditions,

3. malpositioning of the part-length CEA groups,

4. excessive insertion of full length CEA groups.

C. Insertion or with'drawal of full-length CEA subgroups (2) including: -

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1. uncontrolled insertion or withdrawal of a single CEA subgroup from critical conditions,

' dropping of a single CEA subgroup, 2.

3. static misalignment of CEA subgroups comprising a ,

designated CEA group.

D. Insertion or withdrawal of a single full-length or part-leng;h CEAI3) including:

1. uncontrolled insertion or withdrawal of a single CEA from critical conditions,

2. a single dropped full or part-length CEA,

3. a single CEA sticking, with the remainder of the CEAs in that group moving, .

4. a statically misaligned CEA.

(1) A CEA group is any combination of one or more CEA subgroups which are operated and positioned as a unit.

/2) A CEA subgroup is any one set of four or five syrmetrical CEAs.

s (3) A CEA is a complement of poison rods connected to the same extension shaf t and driven by the same drive mechanism.

Page*1S of 203

E. Excess heat removal due to secondary system malfunctions

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including:

1. excess feedwater flow, .

2. excess steam flow caused by inadvertent opening of turbine bypass valves,

3. excess steam flow due to inadvertent opening of turbine control valves, - -

4. decrease in feedwater enthalpy.

F. Change of forced reactor ' coolant flow including simultaneous loss of electrical power to r.11 reactor coolant pumps at 100% power.

G. Inadvertent depressurization of the reactor coolant system including actuation of full spray flow without proper perfor-mance of any pressurizer heaters.

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H. Decrease in heat transfer capability between the secondary and reactor coolant systems including:

1. complete loss of main feedwater flow,

2. loss of external load.

I. Complete loss of AC power to the station auxiliaries.

J. Uncontrolled boron dilution.

K. Asymmetric steam generator transients due to instantaneous closure of one MSIV.

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POSTULATED ACCIDENTS

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i The postulated accidents that are used to determine the design requirements for the subject trips are as follows: .

a. Reactor coolant pump shaft seizure,

b. Steam generator tube rupture.

The CPC's are designed to provide a reactor trip when required for the above anticipated operational occurrences and postulated accidents when initiated from a power level greater than the CPC operating bypass power setpoint.

2.4 ADDITIONAL BASES FOR TRIP SETPOINTS The subject trip systems in conjunction with the remaining Reactor Protective Systems (RPS) must be capable of providing protection p ,

for the design basis events given in Section 2.2, provided that

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at the initiation of these occurrences the Nuclear Steam Supply System (NSSS), its systems, components and parameters are maintained within operating limits and limiting conditions for operation (OL and LCO). .

2.4.1 Relationship Between Monitorino and Protection Systems

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The designs of the monitoring and protective systems are integrated with the plant technical specifications (in which operating limits and limiting conditions for' operation are specified) to assure that all safety requirements are satisfied. The plant monitoring systems, protection systems and technical specifications

. thus complement each other. Protection systems provide automatic action to place the plant in a safe condition should an abnormal event occur. The technical specifications set forth the allowable ~

regions and modes of operation on plant systems, componer.u and Q

Page 20 of 403

parameters. The monitoring systems (meters, displays, and syst. ems

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such as COLSS assist the operating personnel in ,

enforcing the technical specification requirements. Making use of the monitoring systems, protection system and technical specifi-l cations in the manner described above will assure that if, (1) I the operating personnel maintain all protective systems settings at or within allowable values, (2) the operating personnel maintain actual plant conditions within the appropriate limiting conditions .

for operation, and (3) equipment other than that causing an abnormal event or degraded by such an event operates as designed, then all anticipated operational occurrences or postulated accidents will result in acceptable consequences.  !

2.4.2 CPC Timing The limiting event with respect to CPC timing requirements is that event which results in the most rapid approach to the DNBR

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safety limit. It is this event which determines the limiting CPC time response for the low DNBR trip., .

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Q 3.0 SYSTEM REQUIREMENTS The following sections describe the system elements required for performance of the CPC proteci. ion function. Section 3.1 describes the input and output signals that must be provided to the CPC protection programs. The structure and interaction of the CPC protection algorithms is described in Sections 3.2 through 3.4. {

I These sections provide information regarding the structure of the protection software, execution frequency of each protection program, sampling rates for input parameters, and communication among protection programs. Section 3.5 describes the necessary provisions for operator interaction with the CPC System. The requirements for initialization of the CPC algorithms are specified in Section 3.6. Interlocks and permissives required for the . <

system are described in Section 3.7. Requirements related to hardware and sof tware qualification are defined in Reference 1.5.2. -

3.1 -

INPUTS AND OUTPUTS ..

Table 3-1 lists the CPC process input signals for each channei.

Figure 3-1 is a system diagram that shows the allocation of input sig'nals to each channel. Each CPC channel is required to have appropriate signal processing to provide for digital words accessible to the FLOW program (refer to Section 4.1). Each digital word must represent a value that is inversely proportional to the speed of one of the four reactor coolant pumps.

The temperature, pressure, excore detector, and CEA position inputs shall be analog signals proportional to the value of the respective measured process variable. The accuracy requirements in Table 3-1 establish the maximum allowable uncertainty introduced by the conversion of input signals to internal binary format.

The uncertainties given in Table 3-1 are the total uncertainties O attributable to the following:

Page 2Y of 283

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[. L. .'_ .l Table 3-1_

CPC Process Input Signals Number Represen-per CPC tative Signal Accuracy Signal Channel Description Range Tyoe Required -

Reactor Coolant 4 Reactor coolant pump Pump Speed shaf t speed.

Cold Leg 2 Temperature in 465'F analog 11.0*F Temperature primary coolant cold -615'F legs, 1 of the 2 for each steam generator Hot Leg 2 Temperature in 525'F analog il.0*F Temperature primary coolant hot -675'F

, legs 1 and 2 Pressure 1 Pressurizer pressure 1500-2500 analog 16.00 psia Psia ,

Ex-Core Neutron 3 Excore neutron 0-200% analog 10.5%

Flux detector signals __

Deviation 2 CEA deviation Penalty Factor penalty factor from CEACs ,_,

CEA Position 23 Target CEA position 0-100% analog withdrawal _

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1) loading effects

2) reference voltage supply regulation

3) electrical noise .

4) linearity . .

5) A/D converter power suppiy sensitivity .

, 6) quantization.

Each of the two CEA deviation penalty factors shall be a digital .

word received from one of two CEA Calculators (Ref. 1.5.3).

Application of the deviation penalty factors is described in i I Sections 4.2 and 4.4.  !

l The output signals for each CPC channel are listed in Table 3-2.

The two trip outputs are required to be input to the Plant Protec- .

l tion System for use as DNBR and LPD trip signals. The two pretrip outputs are required to initiate CEA Withdrawal Prohibit (CWP) signals within the Plant Protection System. All five contact eutPets mest ecteet, ePeretor eierms. 18e emelog omtPuts for O..

DNBR margin, LPD margin, and neutron flux power are required to I drive analog metcrs that are monitored by the operator. The analog output for core coolant mass flow rate is required for comparison of CPC calculated flow to measured flow during startup l

. testing.

In addition to the ir.put and oatput capabilities discussed above, a device is required to hilow the operator to modify a limited set of constant parameters and to interrogate a broad set of parameters within the software. The operator interface is described in more detail in Section 3.5. - -

3.2 PROGRAM STRUCTURE The CPC design bases require that the system calculate conservative, but relatively accurate, values of DNBR and peak linear heat Page 27 of M3 -

Table 3-2 '

CPC Output Signals ,

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Signal g Rande Low DNBR Trip Contact Output 0, 1 (logical) .

Low DNBR Pretrip Contact Output 0,1 (logical)

High LPD Trip Contact Output 0, 1 (logical)

High LPD Pretrip Contact Output 0, 1 (logical)

Sensor Failure Contact Output 0, 1 (logical)

Analog 0-10 (unitiess)

Q DNBR Margin I

LPD Margin Analog (0-25 KW/FT)

I Calibrated Neutron Analog 0-200 (% of rated Flux Power power)

Core Coolant Mass Analog 0-2 (fraction of Flow Rate design flow) i l

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g rate. However the algorithms required to achieve sufficiently detailed calculations cannot be executed rapidly enough to provide protection for those design basis events with the most rapid approach to the specified acceptable fuel design limits. In order to achieve a system time response sufficient to accommodate l the limiting design basis events additional dynamic calculations l of DNBR and peak linear heat rate are required. The dynamic calculations must provide conservative estimates of DNBR and peak .

linear heat rate based on changes in the process variables between successive detailed calculations of DNBR and peak linear heat rate. The dynamic calculations must be separated into two programs because adjustments in DNBR based on core coolant mass flow rate must be computed more frequently than adjustments based on the other process variables. The detailed calculations of '

DNBR and peak linear heat rate must also be separated into two programs. The grouping of the detailed calculations must be such that the execution interval of each program reflects the time interval over which the dynamic adjustments to the parameters,

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calculated in that program, are valid. ,

The resultant protection sof tware shall consist of four interde-pendent programs and one subroutine that is accessible to all fou'r programs:

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1) Coolant Mass Flow Program (FLOW),

2) DNBR and Power Density Update Program (UPDATE),

3) Power Distribution Program (POWER),

4) Static DNBR and Power Density Program (STATIC),

5) Trip Sequence Subroutine (TRIPSEQ). . .

The FLOW program shall compute the primary coolant mass flow rate .

and a projected DNBR based on the time derivative'of core coolant mass flow rate. In addition the FLOW program shall service the digital-to-analog converters for analog outputs.

Page .*l9 of 203

The UPDATE program shall perform the following major computatio'ns:

1) Calibrated neutron flux power, i

2) Total thermal power,

3) Core average heat flux,

4) Hot pin heat flux distribution,

5) DNBR and quality margin updated for changes in input parameters,

6) Peak local power density, .

The major computations executed in POWER shall include the following:

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1) Axial shape index (ASI) dependent flow projection constant and DNBR operating limit,

2) Core average axial power distribution,

3) Pseudo hot pin axial power distribution,

4) Three dimensional power peak,

5) Average of the hot channel power distribution.

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STATIC shall compute static DNBR, static hot channel quality, and average enthalpy at the core inlet and outlet.

In TRIP 5EQ, minimum DNBR, quality margin, and peak local power

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density shall be compared to their respective pretrip and trip setpoints. Whenever a setpoint is violated, the appropriate contact output shall be actuated. In addition, trips shall be initiated for core conditions outside the analyzed operating space, low reactor coolant pump speed, hot leg saturation, or internal processor faults including:

1) Fixed point divide fault (division by zero or quotient .

overflow),

2) Floating point arithmetic fault (overflow or underflow).

l 3) Memory parity error, lO .

1 Page 30 of 403 1

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'h,- 4) Illegal machine instruction, ,

5) Failure to meet the tif. ting requirements of Section 3.3.

3.3 PROGRAM TIMI!iG At1D I!;PUT SAMPLIllG RATES Execution of the four programs described in Section 3.2 shall be scheduled on a priority basis. The execution frequency of each protection program shall be fixed, based on the required CPC time ,

response. In addition, the more fre:luently executed programs shall be assigned higher priority. The required execution frequen-I l

cies of the four protection programs are specified in Table 3-3.

The Trip Sequence shall be called by FLOW and UPDATE. Sampling f

of the input signals shall be initiated within the protection programs. Therefore the sampling rate for a given input is the same as the execution frequency of the program that reads that input parameter.

O 3.4 PROGRAM ItiTERFACES ,

Communication among the protection programs must be controlled to ensure that the output of a program is based on a consistent set of inputs. Therefore it is necessary to ensure that the input to a program is not changed until af ter execution of that program is complete. One method of controlling communication between programs is to assign exclusive input and output buffers to each program.

The output of a program is made available to other programs l through its output buffer. The output buffer is updated only when execution of the program is complete. The executive must be p:ohibited from interrupting a protection program while it is reading input from the output buffer of another protection program.

In addition, no protection program may be interrupted while it is transferring data to its output buffer or while the Trip Sequence is being executed.

Page 21 of 203

(^j} Table 3-3 u

Program Execution Intervals and Input '

Sampling Rates Execution / Sampling Program Inputs Sampled Interval

• Remarks ,

D .

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()) 3.5 OPERATOR ItiTERFACE ,

The reactor operator shall be informed of the status of a CSC channel by three mechanisms: .

1) The system generates alarms to ciert the operator to abnormal events,

2) The operator interrogates the system to determine the current value of a particular parameter,

3) The operator reads one of three meters driven by the CPC analog output. .

3.5.1 Alarms and Annunciators Each channel must generate unique alarms for each of the following events:

() *

1) Failure of a sensor,

2) Failure of the CPC channel, .

3) Failure of a CEAC.

Indication of an alarm shall be visual. The executive should prohibit removal of the alarm indication unless the condition causing the alarm no longer exists. The alarm signals also must actuate the plant annunciator.

3.5.2 Displays and Indicators Each channel must have an input / output device that allows interro-cation by the operator. The device must enable the operator to initiate display of the significant parameters stored by the CPC programs, including system inputs, addressable constants and selected calculated variables. All parameters to be displayed

() are listed in Appendix A.

O S

Page 33 of 203

Cot CUSTlott Lt:GlHECRlt:G, INC.

PROPRIETARY INFORI:ATION The three analog meters shall provide the operator with a continuous indication of the DliBR margin. LPD margin, and calibrated , neutron 73 k s' flux power calculated by each CPC channel. The three meters shall be calibrated in engineering units over the following .

ranges: .

1) DNBR Margin 10,

2) LPD Margin 25 kw/ft,

3) calibrated neutron flux power 200%.

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 listed in Table 3-4.

A means shall be provided for automated reentry of addressable con.stants, via floppy disc, whose values are not expected to change or whose values are expected to change very infrequently during the

~

fuel cycle. Those constants are designated as Type Il in Table 3-4.

All other addressable constants are designated as Type I.

3.5.4 Failed Sensor Stack .

1 5

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Page 34 of 203

t Table 3-4

{} NddressableConstants Symbol Definition _

Range I

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Addressable Constants Symbol' Defir:ition Range

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Table 3-5 -

O Failed Sensor ids -

Sensor Sensor Sensor Sensor ID ,

flame ID flame 7 . . . _ - . . . . . . . . . . _ . . . _ _ _ _ _ _ _ . . -

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Table 3-5 (Cont'd.)

Failed Sensor ids .

It0TES: -_

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f3 3.5.5 Tripped CPC Channel Snapshot U

When a trip signal is generated in a CPC channel, a snapshot of CPC variables required for display shall be transmitted to a buffer which shall be accessible by using a teletype. [ .-.-....- . .

O 3.8 initiatiz^ Tron The CPC System must be capable of initializing to steady state operation for any allowable plant operating condition. Initializa-tion must be complete within five (5) minutes of initial CPC System startup or of restart following a channel failure or in-test condition. Until initialization of a channel is complete, all trip outputs must be set in the tripped state. '

Initialization shall be considered to be complete when the following criteria are satisfied:

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Syr.bol Definition Units

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A means is required to bypass the trip and pretrip contact outputs n for a CPC channel when reactor power indicated by the corresponding Plant Protection System (PPS) linear power channel is less than

~4 10 percent. In addition, means shall be provided to adjust the bypass setpoint up to at least 1% power to allow bypass of all CPC channels during low power physics testing. In either case, the bypass shall be implemented such that it must be manually initiated at the input / output device for each CPC channel. A nicans, such as a key switch, must be provided to prevent initiation of the bypass by unauthorized personnel. The bypass must be automatir ally removed from each CPC channel when the respective-PPS linea. power channel indicates that rea_t.or power is greater than the bypass setpoint.

n .

_A Page W of <203  ; '.

p 4.0 ALGORITilM DESCRIPTICN

'w) .

This section includes detailed description of the functions to be performed by the CPC protection algorithms. For each of _

the five programs described below, the sequence of computations required is described in sufficient detail to allow the software designer to specify the coding of the protection algorithms.

4.1 PRIMARY COOLANT MASS FLOW O

• __

4.1.1- Algorithm Input k

The FLOW algorithm requires the following process parameters from other CPC programs:

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Specific volumes for the primary coolant are computed from a curve fit of specific volume versus temperature and pressure.

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n-V 5.1.5 FLOW Output ,

The following quantities are transferred to the output buffer of the Primary Coolant Mass Flow Algorithm for use by other programs:

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O-4.1.6 FLOW Constants Theconstantsrequiredforth[databaseofthePrimaryCoolant _

Mass Flow Program are summarized below. The constants will be provided by the design implementation group. All other flow constants will be provided by the functional design group.

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- Calibrated neutron flux power is calculated from:,

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4.2.4 CEAC Penalty Factors ,

The DNBR an'd LPD penalty factors for control element assembly .

i (CEA) deviation are transmitted to each CPC from two Control Element Assembly Calculators (CEAC). The values from the two ,

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l exis,ts, a visual indication is produced at the CPC input / output l device.

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1 The value of core average power used to compute local power ,

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4.2.10 UPDATE Constants ,

The constants required for the DNBR and Power Density Update .

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1 4.3 POWER OISTR:BUTION ALGORITHM O. .

l The purpose of the power distribution is to campute the core average axial power distribution, pseudo hot pin power distribution, and the three dimensional power peak from the excore detector _

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4.3.1 POWER Input The power distribution algorithm requires the following process parameter inputs from other CPC programs:

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i.3.9 _ Pseudo Hot Pin Power *)istribution The pseudo hot pin relative axial power distribution is calculated using the relative axial power distribution cal.:ulated in Section 4.3.6 and the adjusted planar radial peakir.g factors.

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439 Base Core Coolant Mass Flow Rate The base core coolant mass flow rate is computed for use hi the O

4310 POWER Output i . ,

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I 4.3.11 POWER Constants The constants required for the data base of the Power Distribution _.

Progra'm are listed below. Values of the constants ~

will be provided by the design implementation group. ' Values of the remaining constants will be provided by the functional design group.

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4.4 STAT'C DNBR AND POWER DENSITY .

The purpose of the Static DNBR and Power Density Program is to compute the static val'ues of DNBR, hot channel quality, primary thermal power and maximum hot leg teuperature. In additicn, this program establishes static values of the process variables that, in turn, constitute the baseline conditions for the DNBR update.

4.4.1 Inputs This program requires the following process parameters:

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Parameters The core and hot assembly inlet conditions are calculated as follows.

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Comnutation of Core / Hot-Assembly Fluid Properties Q 4.4.6 The calculations described in this section result in the enthalpy, mass flux, cross-flow and pressure drop axial distributions, for both the core region and hot-assembly channels. The hot-assembly distributions will be used in subsequent calculations. (Section 4.4.7) 1he properties at each node depend on the properties 0f the upstream and downstream nodes. Tiie method of solution is a I

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The hot channel distributirins will be used subsequently in the ~

critical heat flux calculations.

As in the preceeding section, the properties at each node depend on the properties at both the upstream and downstream nodes. Again the method of solution is by The technique is summarized below: .

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O 4.4.9 Hot Channel Heat Flux Distributions The calculations described in this section result in the hot-channel critical heat flux and actual local heat flux distributions.

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The enthalpy in both hot legs and both cold legs is computed from the measured temperatur's and pressures. If the averag, hot leg temperature is at its lower range limit.

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r The preceeding calculations make use of the VOLUME functions

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• VP, VFRIC and V will be collectively referred to as " VOLUME".

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p 4.4.15 STATIC Outputs The following variables are written to the St'atic DNBR and Power' Density Program output buffer for use ry other programs:

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4.4.16 STATIC Constants The constants required for the Static DNBR and Power Density Program are given below. These constants will be provided by the functional design group. However, the design implementation e _

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logical "0") are generated. I Oo 4.5.1 Input to the Trip Sequence Alcorithm The trip sequence algorithm requires the following process parameters from other CPC algorithms: '

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First, determine the minimum, calculated value of DiiBR and compensate for any uncertainty in calculation:

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t If DtlBR Trip or Pre-Trip limits are violated, or if Quality' Margin Trip or Pre-trip limits are violated, issue a DilBR Trip or Pre-Trip signal:

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. 1 If Local Power Density Trip or Pre-Trip limits are violated, issue a local Power Density Trip or-Pre-Trip signal: -

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. The folleuing constants, required for the Trip Sequence, will be V provided by the functional design group: _ . _ .

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ENCLOSURE 5 1

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