ML20235Z088

Safety Evaluation Supporting Amend 112 to License DPR-61

ML20235Z088
Person / Time
Site:	Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png
Issue date:	03/07/1989
From:	Office of Nuclear Reactor Regulation
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ML20235Z069	List: ML20235Z065 ML20235Z086 ML20235Z088
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NUDOCS 8903150124
Download: ML20235Z088 (9)

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• UNITED STATES g

.E. o NUCLEAR REGULATORY COMMISSION s j WASHINGTON, D. C. 20566

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. ll2 TO FACILITY OPERATING LICENSE NO. DPR-61 CONNECTICUT YANKEE ATOMIC POWER COMPANY HADDAM NECK PLANT DOCKET NO. 50-213, INTRODUCTION By letter dated February 10, 1989, Connecticut Yankee Atomic Power Company (the licensee) requested changes to plant Technical Specification (TS)

Section 3.11.B. Containment Integrity, for the Haddam Neck Plant. The proposed TS change provides'a one-time relaxation of containment integrity requirements to. allow the service water side of the four containment air recirculation (CAR) fan heat exchangers to be cleaned while the plant is at power.

On December 16, 1988, the licensee found that the four CAR units provided inadequate cooling capability, and therefore, declared them to be inoperable. 1 The CAR fan system is designed to depressurize and cool the reactor containment '

following a loss of coolant accident (LOCA). Subsequently, the licensee provided a justification for continued operation (JCO), which placed a number of restric-tions on plant operation with the degraded CAR fan system. One of those restric-tions was to limit the service water (Connecticut River) supply temperature to less than 50*F. The licensee identified that the flow in the CAR cooling coils was partially blocked, and therefore, the cooling capability of the CAR system was reduced. As part of the efforts to restore the cooling capability of the CAR units before the 50*F limit is reached, the licensee developed the following procedures to clean the CAR coils without shutting down the plant. I However, the proposed cleaning operation would violate the existing contain-ment integrity TS, thus necessitating the proposed temporary change.

The cleaning operation will require removal of all the four CAR units one at a L

time for a period not to exceed seven days for each unit. Each CAR unit is com-prised of five cooling coils. When the CAR cooling coils are removed from their flanged elbows to be cleaned, blank flanges will be installed and leak tested in order to maintain containment integrity. In the process of removing the CAR coils and installing the blank flanges, the service water piping inside contain-ment will be opened to the containment atmosphere and current TS Section 3.11.8 will be violated. Therefore, the licensee proposed changes to TS Section 3.11.B to allow a one-time relaxation of containment integrity requirements with compen-satory measures in place as discussed below.

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,' -2 I EVALUATION L

The licensee stated that the current plant TS require that only three CAR units I

be operable whenever the reactor is critical, and current administrative controls l allow a fourth CAR unit to be removed from service for up to 7 days. In l addition, the licensee's evaluations in support of the JC0 confirmed that fcur i service water pumps and three operable CAR units in their degraded condition l with a service water temperature less than 50*F are adequate to meet all normal l and post-accident service water cooling requirements. Therefore, taking one l

CAR unit out of service for less than 7 days during the cleaning operation does not violate the CAR system TS. However, it will affect the containment integrity TS.

Current TS Section 3.11.B requires containment integrity to be maintained whenever the reactor coolant system is above 300 psig and 200'F. The proposed changes add the following footnote to TS Section 3.11.B:

"The service water piping (containment boundary) for each CAR fan heat exchanger may be opened for up to 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> at a time to install or remove blank flanges. If containment integrity is not restored within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />. The cumulative time for the service water piping to be open shall not exceed 64 hours7.407407e-4 days <br />0.0178 hours <br />1.058201e-4 weeks <br />2.4352e-5 months <br />. The four CAR fan heat exchangers may be cleaned only once during Cycle 15 under this specification."

i The above change is necessary because the process of cleaning the CAR cooling I coils will require the service water piping inside containment to be opened to containment at:nosphere for a period up to 64 hours7.407407e-4 days <br />0.0178 hours <br />1.058201e-4 weeks <br />2.4352e-5 months <br /> since it takes up to 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> each time to install and remove the blank flanges. Thus, for four CAR units to be cleaned sequentially, the process will take 64 hours7.407407e-4 days <br />0.0178 hours <br />1.058201e-4 weeks <br />2.4352e-5 months <br /> total. If a LOCA should occur during this period, the radioactive gases in the containment could be 3 released through the service water piping to the environment which could exceed the allowable offsite dose. To provide alternatives to TS Section 3.11.8 for the period of installing and removing the blank flanges, the licensee proposed the following compensatory measures. Prior to the service water piping being i opened, the service water supply manual valve (outside containment) will be closed and a blank installed between the existing mating flanges upstream of the service water return manual valve outside containment. Pressure above the calculated maximum post-accident containment pressure will be maintained on the closed inlet valve to prevent containment leakage, and the outlet blank flange will be leak ttsted. Thus, during the period that the service water piping may be open, the containment barrier will be the manual valve, the seismically qualified piping on the CAR unit supply side, and the blank flange and associated piping on the return side. The return piping outside containment between the containment penetration and the discharge valve was built to ANSI B31.1,- 1955 standards.

The staff has reviewed the licensee's proposed compensatory measures and has determined the following. The service water supply to each CAR unit consists of a six inch supply line penetrating containment at P-55, 56, 57, and 58. Each supply line has a check valve inside containment. Each CAR unit consists of five sections connected together by a header along with common vent and drain connections. The return lines are also six inch piping which penetrate contain-ment at P-51, 52, 53 and 54 Each return line has a manual ball valve outside containment. The four return lines are joined together downstream of the ball valves by a header prior to entering the discharge tunnel. Since the return piping outside containment is not seismically cualified and the supply line

manual valves are not subject to Appendix J. Type C leak testing, the compensa-tory measures do not satisfy the containment integrity guidelines cf Standard Review Fian (SRP) Section 6.2.4.

However, in case of a LOCA, a check valve in series with a closed inlet valve sealed with water at higher pressure in the opposite direction of the accident releases from the supply line, and the blank flange in the return line would prevent any post-LOCA releases to the environment through the service water line. This configuration is taken as an alternative to the containment integrity criteria of the SRP for et most 64 hours7.407407e-4 days <br />0.0178 hours <br />1.058201e-4 weeks <br />2.4352e-5 months <br />. For such a short duration, the staff believes that the 3roposed compensatory measures provide adequate protection against unaccepta)le radioactive releases. Therefore, the staff finds the licensee's proposed CAR units cleaning operation at power and the associated interim TS change for ensuring containment integrity to be acceptable. Since the compensatory measures are important to the staff's acceptance, the staff reconnends that the footnote in the proposed TS change be modified to state

... install or remove blank flanges. During this time, compensatory measures will be taken. ...", thereby providing further assurance that containment in-Te'grity can be maintained as necessary during the cleaning operation. The licensee has agreed to include this additional wording.

FINDINGS Based on the above, the staff concludes that the licensee's proposed technical specification change and plans to clean the CAR fan heat exchangers at power with compensatory measures in place for maintaining containment integrity are adequate to ensure that unacceptable offsite releases will not occur in the '

event of a LOCA during the interim period while the cleaning operation is pursued.  ;

The staff, therefore finds the proposed change acceptable with incorporation of reference to the compensatory measures in ths interim TS as agreed to by the licensee.

EXIGENT CIRCUMSTANCES p ..A l The Commission's regulations,10 CFR 50.91, contain provisions for issuance of i amendments when the usual 30-day public notice period cannot be met. One type l of special exception is an exigency. An exigency is a case where the staff and licensee need to act promptly, but fa1%re to act promptly does not involve a plant shutdown, derating or delay in startup. The exigency case usually represents an amendment involving a safety enhancement to the plant.

Under such circumstances, the Connission notifies the public in one of two ways: by issuing a Federal Register notice providing an opportunity for hearing and allowing at least two weeks for prior public comments, or by issuing a press release discussing the proposed changes, using the local media.

In this case, the Commission used the first approach.

Pursuant to 10 CFR 50.91(a)(6), CYAPCO submitted the request for amendment on February 10, 1989 asking the NRC to approve this proposed amendment under exigency circumstances. It was noticed in the Federal Register on February 17, 1989 (54 FR 7311), at which time the staff proposed a no significant hazards consideration determination.

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l As a result of an engineering analysis which resulted in all Tour CAR units being declared inoperable, CYAPC0 issued a prompt report in accordance with 10 CTR 50.72.b.1.11.0 on December 16, 1988. A Justification for continued i operation (JCU) was prepared and made available to the NRC on December 18, 1988.

The JC0 placed several restrictions on plant operation, including river water temperature and CAR cooling coil blockage. CYAPC0 had stated the river water temperature restriction could be increased if the CAR cooling coils were cleaned. This is because the CAR cooling analysis is based on 55% CAR cooling coil blockage. Since December 16, 1988, CYAPC0 has initiated several efforts, on a high priority basis, to determine how the CAR cooling coils should be cleaned and whether it was feasible to perform these activities while at power.

These efforts were complete prior to processing the proposed license amendment.

A review of river water temperature history has shown that there is a good probability that river water temperature will exceed the JC0 restriction of 50'F in April. So far it has been a mild winter and river water temperature already has reached the mid-forties on several occasions. Because of the time needed to clean the CAR cooling coils (approximately 4 weeks) and the potential for the river water temperature to exceed 50'F and force the plant to shutdown if the CAR cooling coils are not cleaned, the staff has agreed to review this amendment under exigent circumstances. The licensee did not request emergency' treatment of the amended application; the staff does not believe that an emergency situation exists.

There were no public coments in response to the notice published in the Federal Register.

FINAL NO SIGNIFICANT HAZARDS CONSIDERATION DETERMINATION The Comission's regulations in 10 CFR 50.92 state that the Comission may make a final determination that a license amendment involves no significant hazards considerations if operation of the facility in accordance with the amendment would not: (1) Involve a significant increase in the probability or consequences of an accident previously evaluated; or (2) create the possibility of a new or different kind of accident from any accident previously evaluated; or (3) involve a significant reduction in a margin of safety.

1. Involve a significant increase in the probability or consequences of an accident previously evaluated. In the process of cleaning the CAR cooling coils, the CAR units will be removed from service one at a time. A design basis accident (DBA) LOCA or steam line rupture coincident with a failure of one of the three operable CAR units could result in insufficient cooling of containment. Thus, containment design pressure and/or temperature could potentially be exceeded. However, the Haddam Neck Plant Tecinical Specifications require that only three CAR units be operable whenever the reactor is critical and current administrative controls allow a fourth CAR unit to be removed from service for up to seven days. Since the unavailability of the CAR system due to the cleaning process is equivalent to the unavailability already permitted by the administrative controls, the proposed configuration is allo. M by existing administrative controls, and is equivalent to the existing Tecia.ical Specifications. In addition, the evaluations supporting the JC0 confirm that four service water and three operable CAR units are adequate to meet all service water temperature less than 50'F. Therefore, the consequences of a DBA will not be significantly increased by the removal of a single CAR unit from service for cleaning.

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By opening up the service water piping inside containment, containment integrity will be technically relaxed. If a DBA LOCA were to occur i coincident with a loss of containment, the allowable offsite dose could be exceeded. To ensure that an adequate containment will be in place at all 3 times during the CAR cooling coil cleaning activities, special precautions j will be implemented as a compensatory measure. The service water supply l manual valve (outside containment) will be closed and a blank installed '

between existing mating flanges upstream of the service water return manual valve (also outside containment) prior to the service water piping inside containment being opened. Pressure above the maximum post-accident containment pressure will be maintained on the closed inlet valve to prevent containment leakage. The outlet blank flange will be leak tested.

Although not seismically qualified, the return piping outside containment between the containment penetration and the discharge throttle valve is carbon steel seamless A53 grade A schedule 40. It was built to the then-current standard, B31.1, 1955. (An accident concurrent with a seismic event is beyond the Haddam Neck Plant design basis). In addition, all work in this area of piping will be administrative 1y restricted during these evolutions. Therefore, the compensatory measures will ensure that no significant increase in radiological consequences following an accident will occur as a result of this change. During the allowable maximum of 64 hours7.407407e-4 days <br />0.0178 hours <br />1.058201e-4 weeks <br />2.4352e-5 months <br /> that the service water piping may be open, the containment barrier will be the manual valve and seismically qualified piping on the CAR unit supply and the blank flange and associated piping on the return side.

The proposed change would not affect the probability of a DBA LOCA or a steam line rupture. As stated earlier, administrative controls currently allow a single CAR unit to be removed from service for up to seven days.

Therefore, the probability of failing the CAR fan system will not be significantly affected.

The special procedure regarding isolation of service water supply to the CAR fan unit will not impact service water system availability to other components.

The purpose of the proposed change is to clean the CAR fan heat exchangers.

In so doing, service water flow through the heat exchanger will increase.

This increase in heat removal capacity is necessary to restore the CAR unit performance to that assumed in the Final Safety Analysis Report for the design service water temperature. The net effect of the change will be to improve CAR unit cooling system performance.

2. Create the possibility of a new or different kind of accident from any previously evaluated. Tne poss10111ty for an accident or malfunction of a dirrerent type than any evaluated previously in the Final Safety Analysis Report is not created since the change and/or failure modes associated with the change do not modify the plant response to the poin. here it can be considered a new design basis accident. There are no new railure modes associated with the proposed change which could represent a new unanalyzed accident.

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In addition, our plant-specific Probabilistic Safety Study was utilized to gain additional insight regarding this criterion of the no significant hazards consideration determination.

The probability of having a core damage accident during the 64 hour7.407407e-4 days <br />0.0178 hours <br />1.058201e-4 weeks <br />2.4352e-5 months <br /> time frame allowed to install and remove blank flanges on the service water piping inside containment is given by:

probability = (8 x 10-4/yr.) (64 hr.)/(8760 hr./yr.)

= 5.8 x 10-6 where 8 x 10-4/yr. is the currently calculated core melt frequency for internal events and fire (with credit for the oil-filled transformer replacement in the switchgear room during the 1987-88 outage). Since a seismic PRA has not been performed, the above value does not include seismic events.

This value represents the probability of a core damage accident with containment integrity relaxed. Although in the strict regulatory sense, containment integrity is technically relaxed, in actuality the containment barrier is ensured by compensatory measures.

The compensatory measures will provide a containment barrier by closing off the supply and return service water lines outside containment. Based on WASH-1400 type failure rates for large pipe rupture, the probability of the service water piping to and from the CAR fan unit outside containment ,

failingp a one year time frame following a core damage accident is less than 10 . For catastrophic rupture of the isolatio flanges, a conservative analysis gives less than 10-g valves probability and/or blank over a one year time frame.

Assuming a 10-2 conditional probability for failure of the compensatory measures to isolate containment gives probability of core melt accident (nonseismic) = (5.8 x 10-6) (10-2) containment integrity

= 5.8 x 10-8 This probability is sufficiently low that the above accident need not be considered within the design basis of the plant. The basis for this determination is that containment isolation failure in the current configuration has some finite probability, and the incremental increase resulting from the proposed change would be insignificant 1y small.

In addition, a qualitative assessment of the core melt frequency risk associated with a seismic event and a loss of containment integrity during the 64 hour7.407407e-4 days <br />0.0178 hours <br />1.058201e-4 weeks <br />2.4352e-5 months <br /> period was perfonned. Using the Millstone Unit No. 3 seismic hazard curves and the seismic experience data base on inherent seismic capacity of ANSI B31.1 nan-seismically supported piping, it may be shown that the probability of pipe rupture during the 64 hour7.407407e-4 days <br />0.0178 hours <br />1.058201e-4 weeks <br />2.4352e-5 months <br /> period as a result of a seismic initiatiny event is of the same" order of magnitude as the E N b N int h Ity*'repN EN 'abohe "

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The proposed change does not create a new unanalyzed event based on compensatory measures which will be in effect. As described above, the preposed change dcas not increase the prctability of en accident to the point where it should be considered within the design basis of the plant.

3. Involve a significant reduction in a margin of safety. The proposed g change does not impact the consequences of an accident on the fuel or reactor coolant system protective boundaries. The impacts on containment integrity and offsite public dose are sufficiently low as to be considered beyond the design basis of the plant.

The proposed change will allow the opening of the service water piping inside containment for relatively short periods of time. This piping serves as the containment boundary. The relaxation of containment integrity does not represent a significant reduction in the margin of safe ty. As noted above, the compensatory measures which will be imple-mented provide assurance that the containment boundary will be maintained and that the allowable offsite dose limit will not be exceeded.

Based on the above discussion, the proposed change will decrease the margin of safety because of:

a. The compensatory measures to maintain the containment boundary,

b. The relatively short duration when the service water piping inside containment is open, and

c. The unavailability of the CAR fan units is bounded by that allowed by both the Technical Specifications and existing administrative controls.

Based upon the above considerations, the staff concludes that the amendment meets the three criteria of 10 CFR 50.92. Therefore, the staff has made a final determination that the proposed amendment does not involve a significant hazards consideration.

ENVIRONMENTAL CONSIDERATION This amendment changes a requirement with respect to t M installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. We have has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The staff has previously published a proposed finding that the amendment involves no significant hazards consideration and there has been no public comment on such finding. Accordingly, the amendment meets the eligibility) criteria 10CFR951.22(c(9). for categorical Pursuant to 10 CFR exclusion setenvironmental

!51.22(b), no forth in impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.

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l CONCLUSION  !

We have ccncluded, based on the considerations discussed ebove, that l (1) there is reasonable assurance that the health and safety of the l will not be endangered by operation in the proposed manner, and (2)such public ,

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ectivities will be conducted in compliance with the Comission's regulations, '

and (3) the issuance of the amendment will not be inimical to the common defense and security or to the health and safety of the public.

Dated: March 7, 1989 Principal Contributor: C. L1

DhTED: rch'7,.'1989 5

AMENDHENT NO. 112 TO FACILITY OPERATING LICENSE NO. DPR-61' t

49ettitI1511F524 NRC PDR Local PDR Gray File S.-Lainas'(14E4)

B.Boger(14A2)

J. Stolz S.-Norris A.. Wang OGC D.Hagan(MNBB3302)

E. Jordan (MNBB 3302)

B. Grimes (9A2)

T. Meek (4)'(P1-137)

W. Jones (P-130A)

E. Butcher (11F23)

C. Li (801)

ACRS (10) '

GPA/PA ARM /LFMB 0f*l I s

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