Regulatory Guide 1.79

Rev 1, Preoperational Testing of Emergency Core Cooling Systems for Pressurized Water Reactors

ML003740351
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Issue date:	09/30/1975
From:	Office of Nuclear Regulatory Research
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RG-1.79, Rev 1
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U.S. NUCLEAR REGULATORY COMMISSION

REGULATORY GUIDE

OFFICE OF STANDARDS DEVELOPMENT

REGULATORY GUIDE 1.79 PREOPERATIONAL TESTING OF EMERGENCY CORE COOLING

SYSTEMS FOR PRESSURIZED WATER REACTORS

A. INTRODUCTION

General Design Criterion 1, "Quality Standards and Records," of Appendix A, "General Design Criteria for Nuclear Power Plants," to 10 CFR Part 50, "Licensing of Production and Utilization Facilities," requires that structures, systems, and components of nuclear power plants important to safety be tested to quality standards commensurate with the importance of the safety func tions.to be performed. Criterion XI, "Test Control," of Appendix B, "Quality Assurance Criteria for Nuclear Power Plants and Fuel Reprocessing Plants," to 10 CFR

Part 50 requires that a test program be established to ensure that all testing required to demonstrate that structures, systems,-and components will perform satis factorily in service is identified and performed.

Regulatory Guide 1.68, "Preoperational and Initial Startup Test Programs for Water-Cooled Power Reac tors," describes a method acceptable to the NRC staff for complying with the Commission's regulations with regard to preoperational testing of nuclear power plant structures, systems, and components that perform safety-related functions.

This guide describes a preoperational test program acceptable to the staff specifically for emergency core cooling systems (ECCS) in pressurized water reactor power plants. Although this guide is applicable to all pressurized water reactors, certain aspects may not be completely applicable to specific nuclear steam supply designs. The Advisory Committee on Reactor Safeguards has been consulted concerning this guide and has concurred in the regulatory position.

• Unes indicate substantive changes from previous issue.

Revision 1 September 1975

B. DISCUSSION

The NRC staff has concluded as a result of recent inspections and reviews of safety analysis reports and startup reports that additional guidance should be provided regarding the scope and reporting of ECCS

preoperational testing identified in paragraph 9, "Emer gency Core Cooling Systems," of Appendix A to Regulatory Guide 1.68.

C. REGULATORY POSITION

A comprehensive preoperational test program on the emergency core cooling system and its components

"should be performed to provide assurance that the ECCS

will accomplish its intended function when required.

The program should cover all test-related activities including:

1. 'he development of test descriptions, test objectives, and specific acceptance criteria;

2.

• The preparation of test procedures;

3. Conduct of the tests and acquisition.of system and component performance data; and

4. Resolution of deficiencies and deviations from expected performance.

1.

System Testing The preoperational testing of emergency core cool-I

ing systems should include the tests described below.

USNRC REGULATORY GUIDES

Comments should be sent to the Secretary of the Commission. U.S. Nuclear Regulatory Commission. Washington, D.C. 20M. Attention: Docketing and Regulatory Guides are issued to describe end make available to the public Service Section.

methods acceptable to the NRC staff of implementing specific parts of the Commission's regulations. to delineate techniques used by the staff in evalu- The guides are issued in the following ten broad divisions:

sting specific problems or postulated accidents, or to provide guidance to appli cents. Regulatory Guides are not substitutes for regulation

1. Power Reactors

1- Products with them is not required. Methods and solutions different from those set out in

2. Research and Test Reactors

7. Transportation the guides will be acceptable if they provide a basis for the findings requisite to

3. Fuels and Materials Facilities S. Occupational Health the issuence or continuance of a permit or license by the Commission.

4. Environmental and Siting S. Antitrust Review Comments and suggestions for improvements in these guides are encouraged S. Materials and Plant Protection

10. General at all times. and guides will be revised, as appropriate, to accommodate cam Monts and tO reflect new information or experience. This guide wao revised as a Copies of published guides may be obtained by written request indicating the result of substantive comments received from the public and additional staff divisions desired to the U.S Nuclear Regulatory Commission. Washington. D-C.

review

20565. Attention: Director. Office of Standards Development.

"I1

a.

High-Pressure Safety Injection (HPSI)

The preoperational test program should provide for testing of each train of the emergency core cooling system under both cold and simulated hot operating conditions prior to fuel loading.

(1) Flow Test - Cold Conditions. The reactor vessel may be open and flooded and the reactor coolant system (RCS) pressure at essentially atmospheric (zero gauge pressure) conditions. No attempt Is made to control the temperature of the water in the storage tank or in the accumulators. This test demonstrates system and component capability by injecting water* from the water storage tank into the reactor vessel through various combinations of injection legs and pumps.

This test should be initiated by the safety injection signal with all affected auxiliary systems in their standard operating mode.

It should be demonstrated that the flow rates delivered through each injection flow path using all pump combinations are within the design specifications.

Verification of proper system activation time should also be obtained. The capability of the HPSI pumps to take suction from the low-pressure safety injection pumps should be demonstrated in those plants that use this scheme to handle the small-break accident. The testing should verify that pump motors will not trip out under maximum possible flow conditions and that adequate margin exists between trip points and maximum oper ating conditions for all pump motor trips.

The adequacy of the electric power supply should be verified by testing under maximum startup loading conditions.

(2) Flow Test -

Hot Operating Conditions.

The intent of this test is to demonstrate, by injecting a small amount of water into the primary system at operating pressure and temperature conditions, that emergency core cooling water can be delivered into the reactor under conditions as close as possible to accident conditions.

The reactor vessel should be closed and the RCS filled and maintained at the proper operating pressure and temperature level. The water level in the pressurizer should be as low as practical. System operation should be initiated by actuation of the safety injection signal. The temperature of the RCS will be much higher than that of the injection water, and there

• Because borated water is not made up until the hot functional testing program is completed, the use of unborated water is acceptable for this test.

will be a thermal shock to the piping and reactor vessel as a result of the hot injection fest of the high-pressure safety injection system (HPSI). The staff has considered the potential for thermal shock damage under these conditions and has concluded that the thermal cycling can be tolerated if the test is terminated as soon as proper valve operation has been verified and the pumps have reached rated flow.

The capability of HPSI to deliver as required under accident conditions may also be verified by analysis based on as-built HPSI pump and system head-capacity curves without subjecting the RCS to cold water shock; however, the operability of the check valves should be demonstrated through testing. Any planned oi unplanned actuation of the safety injection system (SIS) under hot operating conditions during the testing program should be documented in the preopera tional testing summary discussed in Section C.3. Follow ing issuance of the operating license, any planned or unplanned actuation of the SIS that results in the injection of cold fluid into the hot reactor coolant system may be classifiable as a reportable occurrence as defined in Regulatory Guide 1.16, "Reporting of Oper ating Information - Appendix A Technical Specifica tions."

b.

Low-Pressure Safety Injection (LPSI)

(I) Flow Test - Cold Conditions. Flow testing of LPSI should be conducted in a manner similar to that for the HPSI (see regulatory position 1.a(I) above).

(2) Recirculation Test - Cold Conditions. The nbjective of this test is to demonstrate the capability to realign valves and injection pumps to recirculate coolant from the containment floor or sump into the reactor coolant system. The testing should include taking suction from the sump to verify vortex control and acceptable pressure drops across screening and suction fines and valves. To avoid RCS contamination, the sump water may be discharged to external drains or other systems.

The testing should verify that the available net positive suction head is greater than that required at accident temperatures as discussed in Regulatory Guide

1.1 (Safety Guide 1, 11/2/70), "Net Positive Suction Head for Emergency Core Cooling and Containment Heat Removal System Pumps." Temporary arrangements may be made to provide adequate sump capacity for pump operation.

c.

Core Flooding

(1) Flow Test - Cold Conditions. The purpose of this test is to demonstrate proper system actuation and to verify that the flow rate is as expected for the test conditions. The accumulators should be discharged

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one at a time into the reactor vessel after being filled to their normal level and pressurized, usually with nitrogen.

Accumulator pressure is not critical and' the test may be conducted at any pressure up to normal precharge pressure. The discharge flow rate may be calculated, from measurements of the change in accumulator water Ilevel versus time. These tests apply to all passive injection systems.

(2) Isolation Valve Test. At most nuclear power plant facilities the control circuit of the accumu lator isolation valves receives a confirmatory open signal whenever the safety injection signal is activated to ensure that inadvertent valve closures do not prevent operation of the core flooding system if required.

At facilities that have this design feature, it L should be demonstrated that the valve will open under the maximum differential pressure conditions of zero RCS pressure and maximum expected accumulator precharge pressures. This capability should be demon.

strated with both normal and emergency power supplies.

(3) Flow Test Hot Operating Conditions.

The intent of this test is to verify that the checkvalves that see higher-than-ambient temperatures during power operation will function at the higher tempera tures.

Initially, the' RCS and the accumulators should be at their normal operating temperature1 and pressure conditions, with the RCS pressure higher than accumulator pressure. Each accumulator injection train should be tested individually or simultaneously by opening the isolation valve and then slowly decreasing RCS pressure and temperature until the check valves operate as indicated by a decrease in the fluid level of each accumulator. TO minimize the thermal cycling, the isolation valve should be closed as soon as check valve operation is verified.

If operability of these valves at high temperature is demonstrated during a different phase of the testing program, this specific test may be eliminated.

2.

Component Testing The components of the systems involved in the system test described in regulatory position I should be tested, either in conjunction with the system tests or in independent component tests. Performance data should be recorded and the following items verified:

a.

Instrumentation

(1) Proper operation of initiating instrumenta tion in all combinations of logic and instrument channel trip.

(2) Proper functioning of instrumentation and alarms used to monitor system availability.

b.

Valves

(1) Proper operation of system valves including response times. This requires visual verification as well as proper control Voom indication.

(2) Valve operation under maximum expected differential pressure conditions (consistent with system test limitations).

(3) Operability at maximum expected tem perature (consistent with system test limitations).

c.

Pumps and Motors

(1) Proper operation of injection pumps and motors in all design operating modes.

(2) Acceptable net positive suction head per formance under maximum system flow conditions.

(3) Adequacy of individual pump capacity and discharge head.

(4) Pump response time (time to reach rated flow conditions).

(5) Proper pump motor start sequence, over speed protection, and adequate margins between motor running currents and protective breaker ratings.

(6) Acceptable vibration levels.

d.

Controls (I) Proper operation of controls, including the controls that effect transfer of pump suction.

(2) Proper operation of interlocks and equip ment protective devices in pump and valve controls.

e.

Power Supplies

(1) Proper operation of alternative electric power supplies used for system valves, pumps, and motors.

(2) Proper operation of automatic and manual power transfer switches.

f.

System Piping and Supports Acceptability of .system piping movements under system startup conditions and during steady-state operation.

g.

Auxiliary Feedwater System Confirmation that the auxiliary feedwater system actuates and supplies feedwater to the steam generator.

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3. Documentation The preoperational testing program should be documented in a summary report and retaine4 as part of the plant. historical record. This summary report should include:

a.

A listing and description of the objectives of each test;

b.

How each test was conducted;

c.

The parameters monitored;

d.

Comparisons and evaluations against design predictions or system performance requirements for the high-pressure safety injection flow tests, the low-pressure safety injection flow and recirculation tests, and the core flooding tests;

e.

Deficiencies noted;

f.

System modifications and corrective actions required;

g.

Appropriate justification for acceptance of systems or components not in conformance with design predictions or performance requirements; and I.

Conclusions.

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Retention of the test procedures, data, and sum maries by the licensee should be consistent with para graph 9 of Appendix C of Regulatory Guide 1.68,

"Preoperatlonal and Initial Startup Test Programs for Water-Cooled Power Reactors," and in accordance with Criterion 1, "Quality Standards and Records," of Appendix A and Criteria XI, "Test Control," and XVII,

"Quality Assurance Records," of Appendix B to 10 CFR

Part 50.

D. IMPLEMENTATION

The purpose of this section is -to provide informa tion to applicants and licensees regarding the NRC staff's plans for utilizing this regulatory guide.

This guide reflects current regulatory practice.

Therefore, except in those cases in which the applicant proposes an acceptable alternative method for comply ing with specified portions of the Commission's regula tions, the method described herein will be used in the evaluation of submittals for operating license or con struction permit applications for which the issue date of the Safety Evaluation Report (SER) is April 1, 1976, or after.

Until April 1, 1976, the staff will continue to evaluate applications on the ,basis of the regulatory position of the June 1974 version of Regulatory Guide

1.79.

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