ML20155G946

Summary of 860423 Meeting W/Util Re Request for Exemption from GDC 35 & Results of Small Range of Break Sizes in Loop of RCS Analysis

ML20155G946
Person / Time
Site:	Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png
Issue date:	05/01/1986
From:	Frank Akstulewicz Office of Nuclear Reactor Regulation
To:	Office of Nuclear Reactor Regulation
References
NUDOCS 8605090343
Download: ML20155G946 (18)

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UNITED STATES

% C} i e i lg NUCLEAR REGULATORY COMMISSION y

j WASHINGTON, D. C. 20555 9,

%.."... #g May 1, 1986 Docket No.: 50-213 Licensee:

Connecticut Yankee Atomic Power Company Facility:

Haddam Neck Plant

SUMMARY

OF APRIL 23, 1986 MEETING WITH UTILITY REPRESENTATIVES CONCERNING THE REQUEST FOR EXEMPTION FROM GDC 35 i

On April 23, 1986, the staff met with representatives from Northeast Utilities to discuss their request for exemption from General Design Criteria 35. Also discussed were the results of their analyses following the discovery that there was a small range of break sizes in one loop of 1

the reactor coolant system for which safety injection flow in the high pressure recirculation mode may be insufficient to provide adequate core cooling. The discussion was focused in four specific areas. These were:

1) frequency of the adverse LOCA; 2) inservice inspection and testing;

3) small break LOCA results; and, 4) emergency operating procedures.

For the discussion of the accident frequency, CYAPC0 had estimated, using i

WASH-1400 methodology,thatthepg/yearor1per12,500 years rticular range of small break LOCAs had a relative frequency of 8x10 A more 1

detailed dascription of this topic is in the attached slides. The i

licensee stated that these analyses did not take credit for manual recovery to open the subject valves. The staff recommended that the licensee include a reference in the emergency procedure that manual operation of these valves is an alternative to remote operation. The licensee agreed with this suggestion. With the proposed use of the high pressure safety injection recirculation mode, the licensee had g/yr or stimated that the probability of the subject breaks was reduced to 7x10~

I per 140,000 yrs.

i Next, the licensee described the efforts they had taken to assure the i

operability of the subject valves (MOV-874 and MOV-24) and the integrity of the piping in the charging system injection line. The licensee has performed a 100% ultrasonic inspection of all welds in the charging system. They also pressurized the piping between the HPSI and RHR systems to look for leaks and none were identified. The licensee operated the subject valves to assure that they would assume the proper position and seat properly. The valves performed as required. The licensee has made a commitment to verify the operability of these valves every 30 days. The staff concluded that the surveillance tests prepared by the licensee would provide reasonable assurance that the valves were operable without endangering the operation of the plant.

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The licensee's presentation next focused on the results of the small break LOCA analyses and the evaluation of the options considered for breaks of the critical break size. Most of the licensee's analyses were comparisons of pump flow for the various systems to the minimum cooling flow required to remove the core decay heat. A more detailed description is presented in the attached slides. The licensee has established that the use of the charging system was still the first option for mitigating small line breaks.

If this system was not effective, the HPSI and loop fill systems were the other available options, in that order.

The last topic presented was a description of the changes made to the emergency operating procedures to address the unavailability of the charging system recirculation mode. The discussion centered on the logic /

decision points of the procedure. The licensee stated that the procedure included a significant margin to account for any calculational or operational uncertainties. The licensee also stated that all operators will be trained in this procedure prior to assuming duty in the Haddam Neck control room.

Following the discussion, the staff recommended that a note be incorporated into the procedure that identified the option of using the HPSI system in the injection mode should high pressure recirculation be unavailable.

This would alert the operators to an additional cooling method until low pressure recirculation could be used.

In summary, the staff concluded that the licensee had established a valid technical justification for the granting of the temporary exemption. The staff recognized that the ultimate resolution may, for some unforeseen reason, take longer than the planned 1987 outage, but strongly encouraged the licensee tc achieve resolution by the end of the 1987 outage. The staff recommended that the licensee consider independent verification of the valve position for MOV-874 and MOV-24 following the proposed surveillance tests to assure proper alignment of the emergency core cooling systems. The staff also recommended hat the suggestions made for improving the emergency procedures be seriously considered by the licensee.

The licensee stated that it would administratively impose the surveillance tests on the subject valves until a permanent technical specification change could be obtained.

In addition, the licensee agreed to provide a written commitment to upgrade the emergency procedure consistent with the staff recomendations:

to provide independent verification of the valve position for M0V-874 and M0V-24 prior to declaring them operable and to provide a commitment that all operators were trained in the new procedure prior to assuming duties in the Haddam Neck control room.

i The staff concluded that upon receipt of the licensee's written commitments, there would be adequate technical justification for the granting of the temporary exemption with reasonable assurance that the plant would be operated safely.

The licensee's written commitments are contained in a letter dated April 25, 1986.

i NO Francis M. Akstulewicz, Project Manager Integrated Safety Assessment Project Directorate Division of PWR Licensing - B

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Enclosure:

As stated cc: See next page f

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Mr. John F. Opeka Connecticut Yankee Atomic Power Company Haddam Neck Plant CC:

Gerald Garfield, Esquire Kevin McCarthy, Director Day, Berry & Howard Radiation Control Unit Counselors at Law Department of Environmental City Place Protection Hartford, Connecticut 06103-3499 State Office Building Hartford, Connecticut 06106 Superintendent Haddam Neck Plant Richard M. Kacich, Supervisor RDF #1 Operating Nuclear Plant Licensing Post Office Box 127E Northeast Utilities Service Company East Hampton, Connecticut 06424 Post Office Box 270 Hartford, Connecticut 06141-0270 Edward J. Mroczka Vice President, Nuclear Operations Northeast Utilities Service Company Post Office Box 270 Hartford, Connecticut 06141-0270 Board of Selectmen Town Hall Haddam, Connecticut 06103 State of Connecticut Office of Policy and Management ATTN: Under Secretary Energy Division 80 Washington Street Hartford, Connecticut 06106 Resident Inspector l

Haddam Neck Nuclear Power Station c/o U.S. NRC East Haddam Post Office East Haddam, Connecticut 06423 Regional Administrator, Region I U.S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, Pennsylvania 19406 f-

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II.

BACKGROUND

".'he process of code development and experimentation using mode.'.s is expected to continue.

The Commission plans to place the necessary additional emphasis on such work in Commission programs and expects the nuclear industry to accelerate its efforts.

These criteria are applicable to all light-water power reactors except as otherwise provided.

Improvements are expected in analytical techniques, and experimental programs are expected to provide increased and improved knowledge about ECCS performance.

On the basin of such improvements in technology, these criteria, will be modified from time to 1

l time

[ INTERIM ACCEPTANCE CRITERIA, 36 Fed. Reg. 12217-8.]

PART 3 - WESTINGHOUSE EVALUATION MODEL Analyses should be performed for the entire break spectrum, up to and including the double-ended severance of the largest pipe of the reactor coolant pressure boundary.

^

The combination of systems used for analyses should be derived from a failure mode and effects analysis, using the single-failure criterion.

The analytical techniques to be used are described in the topical report, " Westinghouse PWR Core Behavior Following a Loss-of-Coolant Accident" WCAP-7422-L January 1970 (Proprietary), and a supplementary proprietary Westinghouse report, " Emergency Core Cooling Performance,"

received June 1, 1971, and in an appropriate nonproprietary report to be furnished by Westinghouse, with the following exceptions

[ INTERIM ACCEPTANCE CRITERIA, 36 Fed. Reg. 12219 (1971).]

FREQUENCY OF ADVERSE LOCAs P

FREQUENCY OF MEDIUM-CONDITIONAL PROBABILITY BREAK LOCA X

GIVEN A MEDIUM LOCA THAT (0.02 to 0.2 ft2) 0.045 ft{ WEEN 0.02 AND IT IS BE AND IN THE LOOP 2 COLD LEG DISCHARGE

+

i FREQUENCY OF S!!ALL-CONDITIONAL PROBABILITY X

GIVEN A SMALL LOCA THAT BREAK LOCg)

(<0.02 ft IT IS IN THE CHARGING LINE OR CONNECTED PIPING (DOWNSTREAM OF LAST CHECK VALVES) 4 il i

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Frequency of Medium-Break LOCA 6.1 x 10~4/Yr (Mean)

=

(WASH-1400) 0.09 Conditional Probability in

=

i Loop 2 Cold Leg (1/4 loops x 1/3 = 1/12) a 2.7 x 10-3/Yr (Mean)

Frequency of Small-Break LOCA

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0.012 Conditional Probability in

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Charging Line 2 pipe segments I7Il pipe segments) i 8,. 10-5/Yr TOTAL

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(Once per 12,500 years) t

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EFFECT OF PROPOSED HIGH PRESSURE RECIRC REALIGNMENT Provides a means of mitigating adverse breaks (albeit not o

single failure proof)

Non-Mitigated Frequency of Adverse Breaks Current Proposed 7 x 10-0/Yr 8 x 10-5/Yr

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f (Once in 12,500 Yr)

(Once in 140,000 Yr) s o

Provides a diverse means of mitigating loop 1, 3 and 4 LOCAs in the recirc mode o

Reduces the frequency of top five accident sequences 4

identified in the CY Probabilistic Safety Study i

i OVERALL IMPACT ON CORE DAMAGE FREQUENCY Current 4

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Breaks Possible 27%.

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New Alignment 1.5%

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i SMALL BREAK LOCA ANALYSIS Probable Safety Study NULAPS Analysis Identified Range of o

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Previous ECCS Line Up Injection Phase ~) HPSI Pump (4 Loops)

Recirculation Phase -> Charging Pump (Loop #2) l o

Proposed ECCS Line Up Injection Phase -> HPSI Pump,(4 Loops)

Recirculation Phase -) Charging Pump (Loop 52)

HPSI Pump (2 Loops)

Loop Full Header (4 Loops) l l

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PDTENTI AL RECIRCUL ATION ALIGNMENTS DUTSIDE CONTAINMENT INSIDE CONTAINMENT 4-CORE

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4 HPSI FLOW CAPABILITY o

Injection Phase (4 Injection Paths)

Runout

--+ 3 2 5 0 G PM Flow at 1000 PSIA -+ 1900 GPM 4

o Recirculation Phase (2 Injection Patlas)

Runout -+ 2850 GPM Flow at 400 PSIA % 2400 GPM Flow at 1000 PSIA -+ 1700 GPM i

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I CHARGING FLOW CAPABILITY o

Flow at 400 PSIA -y 430 GPM o

HPSI Flow is 5.5 Times Greater than Charging Flow at 400 PSIA GPM During Recirculation o

Minimum HPSI Flow to Maintain Covered Core for Large Break 520 GPM l

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I LOCA ANALYSIS REQUIREMENTS i

s Because HPSI Maintains a Covered Cera During Recirculation o

For all Break Sizes No NULAPS Analysis Required j

IAC Analysis Remain Valid Through Recirculation 4

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BROKEN HPSI RECIRCULATION LINE BREAK a

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i RCS Pressure Decreases Below 165 PSIA, RHR is Activated o

and Provides Flow to Core Through Deluge Lines Assuring i

Acequate Core Cooling For This Break Size

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I May 1, 1986 The staff concluded that upon receipt of the licensef s written commitments, there would be adequate technical justification for ti'e granting of the temporary exemption with reasonable assurance that the plant would be operated safely.

The licensee's written commitments are contained in a letter dated April 25, 1986.

Original signed by Francis M. Akstulewicz Francis M. Akstulewicz, Project Manager Integrated Safety Assessment Project Directorate Division of PWR Licensing - B

Enclosure:

As stated cc: See next page DISTRIBUTION

/

Docket File /

NRC PDR Local PDR ISAP Reading FAkstulewicz CGrimes PAnderson FMiraglia ACRS (10)

NSIC OELD EJordan BGrimes ISAP:DPL-B LA:15 D:ISAP:DPL-B FAkstulewicz:mn PAnde IW CGrimes 5/i/86 6 // /86 r /[ /86