Issue Date: 07/14/86 - 1 - 61709

NRC INSPECTION MANUAL DI

INSPECTION PROCEDURE 61709

TOTAL POWER COEFFICIENT OF REACTIVITY

AT PRESSURIZED WATER REACTORS

PROGRAM APPLICABILITY: 2514, 2515 (Supplemental)

61709-01 INSPECTION OBJECTIVES

01.01 To verify that total power coefficient of reactivity

measurements follow license commitments (e.g., ANSI Standards,

Initial Core Load or Core Reload Analysis Reports) and are in

compliance with Technical Specifications (TS).

01.02 To verify that total power coefficient measurements are

conducted in accordance with licensee procedures, are correct, and

are within their acceptance criteria.

61709-02 INSPECTION REQUIREMENTS

02.01 Review the licensee's procedures for measuring the total

power coefficient of reactivity. Determine the adequacy of these

procedures by comparing them to the license commitment documents of

01.01 above.

02.02 Review the retained records for recent total power

coefficient measurements. If possible, observe actual measurements

as they are conducted. Verify that:

a. Prerequisites and initial conditions were met.

b. Precautions and limitations were observed.

c. Plant conditions were maintained as specified in the procedure. Verify that changes or relaxations of plant conditions

were approved in accordance with TS and by the appropriate

licensee personnel.

Also verify that any other procedural deviations were

similarly approved.

d. Calculations of total power coefficient were performed

correctly, including the application of necessary correction

factors.
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e. Values obtained for total power coefficient were within the

acceptance criteria generated from analytical predictions of

core reactivity.

f. The licensee has properly resolved any discrepancies between

actual measurements and the predicted coefficient values.
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61709-03 INSPECTION GUIDANCE

General Guidance

a. The total power coefficient of reactivity is always measured

following initial core load during the startup phase for a

PWR. Although though this measurement typically is not

conducted following core reloads at PWRs, it is possible that

this measurement would be necessary if a core reload departed

markedly from typical fuel and poison loadings.

b. The total power coefficient is used to confirm the predicted

rates of boration and dilution required to achieve the ramped

moderator temperature program. The ramped moderator temperature program maintains turbine steam supply pressure at its

hot zero-power value. As a result, turbine efficiency is

enhanced and turbine blading damage is reduced.

c. The total power coefficient reflects the combined reactivity

effects of the moderator temperature coefficient (MTC) and

Doppler-only fuel temperature) power coefficient.

1. The moderator temperature coefficient describes the

change in core reactivity resulting from a change in

average core moderator (coolant) temperature.

2. The Doppler-only power coefficient also contributes to

the total power coefficient. Because of resonance

neutron absorption effects, negative reactivity is added

to the core as fuel temperatures rise. Fuel temperatures

increase markedly above moderator temperatures as reactor

power level increases. Although incremental reactivity

changes resulting from fuel temperature changes are

small, marked fuel temperature changes occur in a reactor

core when reactor power changes. Therefore, the reactivity effects of the Doppler-only power coefficient are

significant.

d. The total power coefficient of reactivity is typically

measured at four power levels (e.g., 35, 50, 75 and 90%). The

testing usually involves multiple data gathering transients

at each power level. Strip chart recorders are used to obtain

temperature and other data required for calculations.

Calorimetric data and coolant samples are taken to confirm

reactor power and boron reactivity levels.

e. There are three major procedures conducted to measure the

total power coefficient of reactivity.

1. Moderator Temperature Coefficient Determination. Moderator temperature undergoes ramped changes in

response to operator-initiated reactivity changes at

constant turbine load. Doppler reactivity effects are

near zero since reactor power level remains essentially

constant. This procedure isolates the effects of the

moderator temperature coefficient.
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2. Doppler-only Power Coefficient Determination. Reactor

power undergoes ramped changes in response to turbine

load changes. Operator-initiated reactivity changes

maintain moderator temperature essentially constant.

Moderator reactivity effects are near zero. This

procedure isolates the effects of the Doppler-only power

coefficient. The Doppler-only power coefficient,

together with the value of moderator temperature coefficient from 03.01e.1 and the curve for the moderator

temperature versus reactor power level program, can be

used to calculate an expected value for total power

coefficient.

3. Total Power Coefficient Determination. The total power

coefficient is directly determined by conducting ramped

changes in turbine load while using operator-initiated

reactivity changes to follow a ramped moderator temperature program. If xenon changes are taken into account,

the negative of the reactivity associated with the

operator-initiated reactivity changes is a direct

measurement of the total power coefficient reactivity

defect for the power change.

f. This inspection procedure should be performed during the

startup physics testing sequence for each refueling outage.

03.01 Specific Guidance

a. Inspection Requirement 02.02a. Typical prerequisites and

initial conditions for this measurement are as follows:

1. Operational alignment of the neutron monitoring system

has been satisfactorily completed.

2. The reactivity computer is installed and operational.

3. Strip chart recorders are installed as required by the

licensee's procedure.

4. Chemistry support is available to sample boron concentration at the required intervals and locations.

5. The reactor is critical and the plant is ready to follow

turbine load changes. For example, pressurizer level is

in the normal operating band and steam generator level

control is in automatic.

6. Actual control rod bank configuration is as required by

the licensee's procedure.

7. The detailed reactor power history for the most recent

48-hour period is available.

8. A reactor thermal power measurement (calorimetric) has

been conducted.

9. Control rod worth curves are available.
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b. Inspection Requirement 02.02b. Typical precautions and

limitations are as follows:

1. a limitation on the maximum rate of change of reactor

power

2. control bands to be observed for reactor coolant system

temperature and pressure

3. a maximum reactor power limit

4. positive adherence to unrelaxed core parameter requirements such as hot channel factor or radial or axial flux

peaking limits

5. awareness and understanding of applicable TS requirements

(e.g., group rod height and rod insertion limits)

6. avoidance of primary system makeup during transients

61709-04 REFERENCES

Technical Specifications

Initial Core Load Analysis Report, or

Core Reload Analysis Report

Applicable Fuel Vendor Reports

ANS-19.6.1, "American National Standard Reload Startup Physics Tests

for Pressurized Water Reactors," (1985)

END