ML16340A662

Forwards Summary of NRC Review of Test Procedure 42-7 & Addl Guidance Re Supporting Analyses Required by Branch Technical Position Rsb 5-1

ML16340A662
Person / Time
Site:	Diablo Canyon
Issue date:	10/23/1979
From:	Stolz J Office of Nuclear Reactor Regulation
To:	Morrissey J PACIFIC GAS & ELECTRIC CO.
References
TAC-51638, NUDOCS 7911210131
Download: ML16340A662 (20)

Text

ili W NRC PDR 7Local PDR OCT 23 3%~

LWR 1 File D. B. Vassallo D. Ross F. J. Williams S. Varga J. Stolz B. Buckley E. Hylton R. Nattson S.

Hanauer J.

P. Knight R. Tedesco R.

DeYoung V. Moore Docket Hos. 50-275 and 50-323 Nr. John C. Norr issey Vice President and General-Counsel Pacific Gas 8 Electric Company'7 Beale Street San Francisco, California 94106 W. Kreger N. Ern'st R. Denise ELD IE (3)

D. Eisenhut B. Grimes bcc:

J.

R. Buchanan, NSIC T. B. Abernathy, TIC

$0Q<() i),

SUBJECT:

REQUEST FOR ADDITIONAL INFORMATION (Diablo Canyon, Units 1

8I 2)

At our request, we received from the Office of Inspection and Enforcement a

preliminary draft of Test Procedure No. 42.7 "Natural Circulation Boron Mixing Test" that will be conducted at the Diablo Canyon facility following a decision on the issuance of an operating license.

While we recognize that the above cited draft procedure was not submitted to the Office of Nuclear Reactor Regulation by the Pacific Gas 5 Electric Company for our review, nevertheless, in order to expedite the review of Diablo Canyon we have evaluated this procedure and related material as delineated in Appendix J of Amendment Ho. 60 of the Diablo Canyon FSAR for conformance with Branch

'echnical Position RSB 5-1.

Enclosure 1 provides a sugary of the staff's review of the Test Procedure No. 42.7; Enclosure 2 provides additional guidance in regard to the supporting analyses required by Branch Technical Position RSB 5-1.

In order to expedite the resolution of this issue, we would be happy to meet with your representatives to discuss in detail any questions you may have on this matter.

r Sincerely,,<>~ s. h><@~

DQ Slg C

Enclosures:

1.

Request for Adlitional Information 2.

Additional Guidance cc:

See next page ohn F. Stolz, Chief Light Water Reactors Branch No.

1 Division of Project Management g ggy si 0 l3/

DF,CE),.

LWR, 1 LWR 1

SURNAME DATE$

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NRC FORM 318 (9.76) NRCM 0240 4 U.S. GOVERNMENT PRINTING OFFICE: 1979'289'369

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OCT 2g 197g Mr. John C. Morrissey cc:

Philip A. Crane, Jr.,

Esq.

Pacific Gas 5 Electric Company 77 Beale Street San Francisco, California 94106 Janice E. Kerr, Esq.

California Public Utilities Commission 350 McAllister Street San Francisco, California 94102 Mr. Frederick Eissler, President Scenic Shoreline Preservation Conference, Inc.

4623 More Mesa Drive Santa Barbara, California 93105.

Ms. Elizabeth E. Apfelberg

.,1415 Cazadero San Luis Obispo, Cali fornia 93401 Ms. Sandra A. Silver 1760 Alisal Street San Luis Obispo, California 93401 Mr. Gordon A. Silver 1760 Alisal Street San Luis Obispo, California 93401 Paul CD Valentine, Esq.

321 Lytton Avenue Palo Alto, California 94302 Yale I. Jones, Esq.

19th Floor 100 Van Ness Avenue San Francisco,'alifornia 94]02 Mr..Richard Hubbard MHB Technical Associates Suite K

1723 Hamilton Avenue San Jose, California 95125 Mr. John Marrs Managing Editor San Luis Obispo County Telegram - Tribune 1321 Johns'on Avenue P.

0.

Box 112 San Luis Obispo, California 93406 Elizabeth S.

Bowers, Esq., 'Chairman Atomic Safety 8 Licensing Board U.

S. Nuclear Regulatory Commission Washington,.D.

C.

20555 Mr. Glenn 0. Bright Atomic Safety 5 Licensing Board U.

S, Nuclear Regulatory Commission Washington, D.

C.

20555 Tolbert Young P. 0.

Box 219 Avila'each, California 93424 Richard S.

Salzman, Esq.,

Chairman Atomic Safety 8 Licensing Appeal Board U.

S. Nuclear Regulatory'ommission Washington, D.

C.

20555 Dr.

W.

Reed Johnson Atomic Safety 5 Licensing Appeal Board U.

S. Nuclear Regulatory Commission Washington, D.

C.

20555 i'lan S. Rosenthal, Esq.

Atomic Safety 5 Licensing Appeal Borad, U.

S. Nuclear Regulatory Commission Washington, D.

C.

20555 Ms.

Raye Fleming 1920 Mattie Road Shell Beach, California 93440 Brent Rushforth, Esq.

Center for Law in the Public Interest 10203 Santa Monica Boulevard Los Angeles, California 90067 Arthur B. Gehr, Esq.

Snell 5 Wilmer 3100 Valley Center

Phoenix, Arizona 85073 Mr. James

0. Schuyler, Nuclear Projects Engineer Pacific Gas 8 Electric Company 77 Beale Street San Francisco, California 94106

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'Mr. John C. Morrissey cc:

Bruce Norton, Esq.

3216 North 3rd Street Suite 202 Phoenix, Arizona 85012 Mr.

W.

C. Gangloff Westinghouse Electric Corporation P,

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Box 355

'ittsburgh, Pennsylvania 15230 Michael R. Klein, Esq.

Wilmer, Cutler

& Pickering 1666 K Street, N.

W.

Washington, D.

C.

20006 David F. Fleischaker, Esq.

Suite 709 1735 Eye Street, N.

W.

.Washington, D.

C.

20006 Dr. William E. Martin Senior Ecologist Battelle Memorial Institute

Columbus, Ohio 43201 W. Andrew Baldwin, Esq.

124 Spear Street San Francisco, California 94105

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I 4

ENCLOSURE 1

REQUEST FOR ADDITIONAL INFORMATION DIABLO CANYON, UNIT 1

!Ae have reviewed the proposed Test Procedure No. 42.7 for the natural circulation boron mixing test at Diablo Canyon, Unit 1; this review also considered the material provided in Appendix J of Amendment No.

60 to the Final Safety Analysis Report (FSAR) dealing with your approach to meet Branch'echnical Position RSB 5-1.

Based on this review, we find that the proposed test procedure does not meet the requirements of RSB 5'-l.

A summary of the staff's review is provided below:

1.

The approach described in Appendix J of Amendment 60 of the FSAR to meet Branch Technical Position RSB 5-1 involves boration without letdown and the use of 12 weight percent borated water (-21,000.ppm boron).

However, test procedure No. 52.7 is based on maximum letdown flow (about 120 gpm at s'tart of test),

and the addition of 10 gpm of 12 weight percent borated water pl'us 10 gpm of unborated water.

This is not representative of boration without

'etdown since (a) most of the mixing should occur in the volume control tank (VCT) with a resultant initial boron concentration of water injected into the reactor coolant system (RCS) of about 2800 ppm boron, (b) the injected

.borated water is at a higher temperature and lower density with letdown of the regenerative heat exchanger'and (c) the velocity of borated water injected into the RCS is initially about seven times larger than that for no letdown.

One:of the staff concerns with respect to boration under natural

- circulation conditions was that mixing would be delayed as the result of stratificati on, and low injection temperatures and v'elocities when high weight percent borated water is used with'out letdown.

The proposed test does not resolve this concern and is th'erefore unacceptable, 2.

The proposed acceptance criteria by Diablo Canyon are unacceptable because they do not address the question of adequacy of mixing.

Since the in'itial boron concentration in the RCS is 1500 ppm, with thorough mixing obtai'ned initially by use of the RCS pumps, and the average concentration of injected water under natural circulation'conditions is greater than 2800 ppm, an acceptable, criterion that the PCS boron concentration remain above 1450 ppm boron during the test is not a meaningful measure of the adequacy of mixing.

I 3.

If, as stated in the proposed test, the reactor is operated at only 5 to 10 percent of full power for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> prior to the test the decay heat rate may be as low as 0.02 percent of full power during the course of the test and would be less than normal.system heat loss.

The natural circulation flow rate is then determined. primarily by the cooldown rate as controlled by the atmospheric dump valves.

The isolated steam generators which act as heat sources during the cooldown tend to suppress natural circulation in these loops.

Since'redictions of natural circulation flow rate were not provided, it is not clear that flow rates in the idle loops will be adequate.

V

4.

The test procedure does not address the testing of cooling of the vessel head region under natural circulation conditions.

This could result in limitation on cooldown and depressurization rates due to vessel stress limits and steam bubble formation in the upper head region.

It should also te noted that steam bubble formation could occur on the primary side of the steam generators.

In telephone discussions with the staff PGE personnel said that Mestinghouse has not completed work dealing, with the upper.

head region.

Hence, procedur'es dealing with this problem have not been written.

This part of the test should be a'ddressed.

5.

From telephone conversations with PGE and Westinghouse personnel, it is concluded that further work to provide the technical basis for the proposed natural circulation test is needed.

A report should be. submitted. to the staff prior to the test which defines the test goals, gives the technical bases for the test, and justifies the acceptance criteria.

The report should include calculations of natural circulation flow rates and loop transit times, estimates of expected boron concentrations, and should address the effects of instrument errors, sample line transient times and instrument response

'times on interpretation of the test results.

This

. report would serve to justify the proposed operating conditions and prd-cedures to be used in the test.'.

Finally a ~eport on the test results should be prepared which describes the test, the interpretation/application of the data, and the use of the results in estimating cooldown times, preparation of operating procedures and sizi.ng of the condensate storage

tank,

ENCLOSURE 2

NATURAL CIRCULATION TEST AND SUPPORTING ANALYSES RE(UIRED IN BRANCH TECHNICAL POSITION RSB 5-1 0

The'functional requirements of Branch Technical Position RSB 5-1, "Design Requirements of the Residual Heat Removal System,"

are as follows:

"Functional Re uirements The system(s) which can be used to take the reactor from normal operating conditions to cold shutdown* shall satisfy the functional requirements listed below.

1.

The design shall be such that the reactor can be takeri from normal

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operating conditions to cold shutdown* using only safety-grade systems.

These systems shall satisfy General Design Criteria 1 through 5.

2.

The system(s) shall have suitable redundancy in components and

features, and suitable interconnections, leak detection, and isolation capabilities to assure that for onsite electrical power system operation (assuming offsite power is not available) and for offsite electric'al power system operation (assuming onsite power is not available) the system function can be accomplished assuming a

sing le failure.

3.

The system(s) shall be capable of being operated from the con'trol room with either only onsit'e or only offsite power available.

In demonstrating that the system can perform its function assuming a

single failure, limited operator action outside of the control room would be considered acceptable if suitably justified.

"Processes'snvo ve in cooldown are heat removal, depressurization, flow circulation, and reactivity control.

The cold shutdown condition, as described in the Standard Technical Specs refers to a subcritical reactor with a reactor coolant temperature no greater than 200 oF for a PWR and 212oF for a BMR.

4.

The yste:..(s) sliall be capable of bringing the reactor to a cold shutdown condition, with only offsite or onsite power available, within a reasonable period of time following shutdown, assuming the most limiting single failure."

For

PWRs, the loss of offsite power results in reactor scram and loss of the main condenser, the main feedwater pumps and the RCS pumps.

The plant can be brought to a hot standby condition with feedwater supplied by the auxiliary feedwater pumps taking suction from the condensate sto'rage tank and with steam discharge to the atmosphere via the atmospheric dump valves or steam generator safety valves.

In accordance with the Standard Review Plan prior'to incorporation of RSB 5-1, the auxiliary feedwater

system, condensate storage tank and safety valves meet safety grade requirements.

The residual heat removal system (RHRS), which was also required to be a

safety grade system prior to incorporation of RSB 5-1, is used to take the reactor to cold shutdown conditions.

However, the RHRS cannot be operated

. in this mode until the RCS.pressure and temperature have been reduced to about 400 psig and 350 F*, respectively,

Hence, the major new impact of the functional requirements of RSB 5-1 on PWR plant design involves the transition region from hot standby conditions down to the conditions permitting operation of the RHRS.

There are four,basic functions involved during plant operation in this transition region when the plant is being taken to cold shutdown.

These are (a) boration of the RCS to the cold shutdown concentration, (b) circulation of the reactor coolant to promote mixing and uniform cooldown, (c) removal of stored and decay heat to reduce the RCS temperature from about 545 F to 350oF and (d) depressurization of the RCS from about 2200 to 400 psig.

With

loss of offsite power, these functions must be accomplished with the

.RCS in a natural circulation condition.

In addition, the requirement that the design be such that, the plant could be taken to cold shutdown using only safety-grade systems has an impact on the systems and procedures used while the plant is operating in this transition region.

For example, the letdown line in the chemical and volume control system has air-operated valves which are supplied by an air compressor whi'ch is not seismic Category l. If the air supply is lost, boration of the RCS under natural circulation conditions and without letdown would be required.

There is insufficient information available to.permit reliable estimates of the times required to achieve adequate mixing of borated water under natural circulation conditions and using the particular systems and procedures specified by the applicant to meet the functional requirements of RSB 5-1.

In additon, there may be other factors involving, for example, vessel stress limits in the upper head region and steam bubble formation which could limit cooldown or depres'surization rates.

Some of the effects which should be considered in.

setting up the tests and supporting analyses are as follows:

A.

Boration 1., stratification leading to delay in mixing time 2.

regional non-uniformity of boron concentration (e.g., pressurizer I

versus loops, idle versus active loops, upper head region versus loops)

0

3.

availability of letdown and auxiliary pressurizer spray 4.

boration versus RCS temperature adequate to maintain margin for shutdown during cooldown B.

Circulati on l.

effect of isolated steam generator 2.

need for circulation promoted by heat removal at steam generator to cool loops, after RHRS in operation since RHRS tends to cool only reactor Heat Removal l.

thermal stress in vessel upper head region could limit cooldown rates 2.

effect of isolated steam generator which acts as heat source during cooldown.

D.

Depressurization 1.

steamy bubble formation in upper heat region which could limit depressurization rate 2.

steam bubble formation on primary side of steam generators (particularly isolated steam generator) which could limit depressurization rate In view of the uncertainties involved in cooldown and depressurization under natural circulation conditions, RSB 5-1 requires that tests for Pl/Rs, with supporting analysis, be conducted to (a) confirm that adequate mixing of borated water added prior to or during cooldown can be achieved under natural-circulation conditions and permit estimation of the time required to achieve such mixing, and (b) confirm that the cooldown under natural circulation conditions can be achieved within the limits specified in the emergency operating proc'.dures.

0 The first goal of the test is to demonstrate that adequate mixing and cooldown during operation in the transition region can be obtained using the procedures, systems and equipment which.have been determined to meet the functional require-ments of RSB 5-1.

Hence, any exceptions to these procedures, systems and equipment should be identified and justified by the applicant, and approved by the staff, on the basis that they do not have a significant effect on the achievement of this test goal.

The second test goal is to obtain information

'which can be used to prepare emergency operating procedures and to determine the'dequacy of sizing of the seismic Category 1 condensate storage tank.

Prior to the test, a report should be submi tted to the staff which-defines the test goals, gives the technical bases for the test and justifies the acceptance criteria.

The report should include calculations of natural circulation flow rates and

'Ioop transit times, estimates of expected boron concentrations, and should consider the effects of instrument errors, sample line transient times and,instrument response times on interpretation of the test results.

This report would serve to justify the proposed operating conditions and procedures to be used in the test and would be reviewed by the staff in conjunction with the proposed test procedures.

Within ninety days after completion of the test"',.

a report on. the test results should be submitted to the staff.

This report should describe the results of the test, the interpretation of the test results, and the use of the results in estimating cooldown times, preparation of operating procedures and sizing of the condensate storage tanks

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