B12219, Requests Extension of 860428 Single Failure Exemption to Respond to Small Break Locas.Plant Mods Cannot Be Completed Until End of Cycle 15 Outage.Probabilistic Safety Study for Permanent Small Break LOCA Response Measures Encl.Fee Paid

Requests Extension of 860428 Single Failure Exemption to Respond to Small Break Locas.Plant Mods Cannot Be Completed Until End of Cycle 15 Outage.Probabilistic Safety Study for Permanent Small Break LOCA Response Measures Encl.Fee Paid

ML20215D137
Person / Time
Site:	Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png
Issue date:	09/30/1986
From:	Opeka J CONNECTICUT YANKEE ATOMIC POWER CO.
To:	Charemagne Grimes Office of Nuclear Reactor Regulation
References
B12219, NUDOCS 8610140006
Download: ML20215D137 (22)

Text

, .

CONNECTICUT YANKEE ATOMIC POWER COMPANY B E R L I N. CONNECTICUT P.o. BOX 270 HARTFORD. CONNECTICUT 06141-0270 TELEFHOt4E 203-66s-5000 September 30,1986 Docket No. 50-213 B12219 Office of Nuclear Reactor Regulation Attn: Mr. Christopher I. Grimes, Director Integrated Safety Assessment Project Directorate Division of PWR Licensing - B U. S. Nuclear Regulatory Commission Washington, D. C. 20555

References:

(1) 3. F. Opeka letter to C. I. Grimes, "Haddam Neck Plant Request for Temporary Exemption from Single Failure Requirements - Probabilistic Safety Study LOCA Analysis,"

dated April 22,1986.

(2) 3.F. Opeka letter to C. I. Grimes, "Haddam Neck Plant e Request for Temporary Exemption from Single Failure Requirements," April 25,1986.

(3) Frank 3. Miraglia letter to 3. F. Opeka, " Exemption from Single Failure Criterion (GDC 35) - Haddam Neck Plant,"

dated April 28,1986.

Gentlemen:

Haddam Neck Plant Small Break LOCA Permanent Resolution Request for Extension of Single Failure Exemption Further to References (1) and (3), Connecticut Yankee Atomic Power Company (CYAPCO) hereby submits a description of the long-term resolution, and schedule for completion of plant modifications, to provide appropriate means for the Haddam Neck Plant to respond to certain small break loss of coolant accidents (SB LOCAs). The NRC, in Reference (3), issued a temporary exemption from single failure requirements to permit utilization of temporary measures to respond to the subject SB LOCAs during the period of Cycle 14 operation. Because some plant modifications necessary to implement a permanent response cannot be completed until the end of the Cycle 15 outage, CYAPLO requests a one cycle extension for a limited element of the exemption issued in Reference (3) with respect to those modifications.

go % h (

BACKGROUND On March 31, 1986,(1) CYAPCO submitted a probabilistic safety study (PSS) in conjunction with the Integrated Safety Assessment Program (ISAP) for the Haddam Neck Plant, which included best estimate loss of coolant accident (LOCA) analyses for that facility. Through these analyses, CYAPCO identified a small range of break sizes in one loop of the reactor coolant system (RCS) for which safety injection flow in the high pressure recirculation mode may be insufficient to provide adequate core cooling. As explained in Reference (1),

CYAPCO had not identified the consequences of such accidents prior to this study because the Commission-approved Emergency Core Cooling System (ECCS) evaluation model used at Haddam Neck did not evaluate this precise scenario.

The temporary measures undertaken by CYAPCO and z.pproved by the NRC to respond to this range of SB LOCAs involved revising Haddam Neck emergency operating procedures regarding LOCA responses to provide, under prescribed conditions, an alternate flow path for core cooling during the high pressure recirculation mode. The revision provides for establishment of the long-term recirculation mode using the high pressure safety injection (HPSI) pumps. Use of the HPSI pumps for this recirculation path requires realignment of certain valves, including two valves, both outside containment, which do not satisfy single failure requirements. Accordingly, CYAPCO requested an exemption from the single failure requirements for these valves, pending implementation of permanent measures which satisfied those requirements (Reference (1)).

Following a meeting with the NRC Staff on April 22,1986, CYAPCO provided in Reference (2) additional information regarding its proposed actions. The implementation of t!)ese proposed actions was confirmed during Resident Inspection No. 86-06.t2) on April 23, 1986, the Staff granted the requested exemption (Reference (3)).(3)

The Staff requested in Reference (3) that CYAPCO provide by September 1986, a description of the long-term resolution of this issue and a schedule for completion of any plant modifications. Accordingly, CYAPCO has performed additional analyses to identify appropriate permanent measures to address the (1) 3. F. Opeka letter to C. I. Grimes, "Haddam Neck Plant Probabilistic Safety Study - Summary Report and Results," dated March 31,1986.

(2) Edward C. Wenzinger letter to 3. F. Opeka, " Resident Inspection 50-213/86-06," dated May 30,1986.

(3) CYAPCO subsequently submitted revisions to the Haddam Neck technical specifications which provided additional assurance regarding the operabil-ity of valves for which the exemption had been granted (3. F. Opeka letter to C. I. Grimes, "Haddam Neck Plant - Proposed Revision to Technical Specifications - Emergency Core Cooling Systems," dated May 14, 1986).

The NRC issued a waiver of compliance from the existing technical specifications (C.I. Grimes letter to 3.F. Opeka," Waiver of Compliance From Technical Specification 3.6.B," dated May 23, 1986) and an amendment to the Haddam Neck operating license to reflect the revised technical specifications (F. M. Akstulewicz, Jr. letter to 3. F. Opeka,

" Technical Specifications for High Pressure Recirculation Emergency Core Cooling Systems," dated July 11, 1986).

P .

postulated range of small breaks. CYAPCO presently plans to install new valves and certain other equipment by the end of the Cycle 14 refueling outage, as originally contemplated in Reference (1). Howev' because permanent electrical modifications cannot be completed until the end of the Cycle 15 outage, it will be necessary to continue to rely on manual operation of the subject valves to respond to these breaks. The completion of additional, previously-planned plant modifications to ECCS circuits by the end of the Cycle 15 outage will allow power operation of the new valves using qualified, redundant circuits.

In Reference (3), the Staff indicated that it may extend the period of the exemption for good cause. Further thereto, CYAPCO requests an extension from a limited aspect of the present exemption, as necessary to allow for completion of electrical modifications by the end of the Cycle 15 outage.

CYAPCO demonstrates below that good cause exists for this extension.

PERMANENT PLANT MODIFICATIONS CYAPCO has evaluated several possible plant modifications as permanent measures to respond to the postulated range of SB LOCAs for which the potential for inadequate core cooling was identified.(4) All options considered were evaluated for their ability to provide adequate coolant injection for the prescribed RCS pressures which CYAPCO has determined to be indicative of SB LOCAs of the pipe and location for which charging high head recirculation may be inadequate.t5i CYAPCO evaluated options utilizing either charging or HPSI pumps under the prescribed conditions. These options are described below, as well as the basis for accepting or rejecting each option. These options are described in greater detailin Attachment 1.

Simultaneous Loop 2 Cold Leg / Loop 4 Hot Leg Injection To establish maximum flow to these injection paths using charging pumps, and to satisfy single failure requirements for this option, would require several plant modifications. First, a r would need to be opened.gqtor-operated valve valves W In addition, redundant parallel in thewould loop need 4 hottoleg (MOV-290)

(4) Briefly, a small range of break sizes in the loop 2 cold leg reactor coolant pump discharge or the charging line may result in inadequate core cooling during the recirculation phase. For these break sizes, the RCS pressure remains above the shutoff head of the residual heat removal (RHR) pumps, thereby preventing activation of low pressure recirculation, while the charging flow provides insufficient flow to maintain core cooling. Break sizes outside this narrow range of breaks are adequately mitigated by the original recirculation method. A full description of these conditions are set forth in Reference (1).

(5) Because the current recirculation method (use of RHR pumps to deliver containment sump water to the charging pumps) is adequate for a range of SB LOCAs, it remains the primary response mechanism. CYAPCO will continue to use that method of cooling unless the prescribed pressure indication is present in which case HPSI will be utilized.

(6) This valve was disabled and locked closed in 1971, in response to concerns regarding steam binding of the hot leg, approved by the AEC.

7 be installed _in series with .MOV-290 in that line to satisfy single failure

requirements. Also, additional flow paths around existing charging flow control

, valves were considered in order to decrease system resistance and increase total flow (flow control valves, even when fully open, are highly restricting). The combined flow paths would provide adequate injection except when the break is postulated to' occur in one of the two injection lines. In that situation, the

, remaining flow path is unable to match RCS boll off until significant RCS depressurization occurs. Consequently, this option was not considered acceptable as a permanent modification.

' Loop Fill Headers Also considered was charging pump injection through the loop fill headers. The

, loop fill header lines are each IM" lines. If the postulated initiating break is in one of these lines the original injection scheme, i.e., high head recirculation

.using charging pumps with injection into the Loop 2 cold leg, would provide adequate cooling. If the postulated initiating break is not in one of these lines this flow path would be available(7) and should provide sufficient core cooling to j keep the core .tempgrature . below the limits established by the Interim 2

Acceptance Criteria.W CYAPCO has determined, however, that this option is i not desirable as the permanent response mechanism. In order to achieve

! injection through these lines it would be necessary to fill the suction legs of the

. cold leg piping between the steam generators and reactor coolant pumps, which 3 could cause some core uncovery as the loop seal is cleared of injection water.

Although adequate core cooling should be maintained, the uncovered core condition is not desirable.

Pressurizer Auxiliary Spray

CYAPCO also explored injection through the pressurizer auxiliary spray using the charging pump. Although not presently single failure proof, installation of a

. parallel valve arrangement would address that condition.' However, if the break i is in the Loop 2 cold leg, the majority of the available flow would be directed out of the break. ' Also, the injection line is only 1% inches in diameter. Thus, the total flow which may be provided, even assuming best case conditions, is not i substantially greater than simply injecting into the Loop 2 cold leg. Accordingly,

CYAPCO concluded that this option does not possess sufficient flexibility to i warrant further consideration.

r HPSI Realignment  !

In the absence of'a fully acceptable modification (described above) using the j charging pumps, CYAPCO investigated utilization of the HPSI pumps to obtain i

(7) In Reference (1), CYAPCO described this path as an additional option to be

! described in procedures but not relied upon as a principal response j mechanism. ,

j- (8) As described in Reference (1), Haddam Neck is governed by the " Interim i Acceptance Criteria for Emergency Core Cooling for Light Water Power Reactors," 36 Fed. Reg.12247 (June 29,1971), Appendix A.

i i - . . - _ - - - _ _ - - - - . - - - ,

=. - - = _ _ - ._ _. . .. -. _

-5

~

adequate core cooling in the event of the postulated SB LOCA.(9) The only feasible alignment of the HPSI pumps is the alignment described in the current limited exemption. Accordingly, CYAPCO has identified specific plant modifications which resolve the existing single failure condition.

As described in Reference (1), the HPSI alignment involves aligning the RHR pump discharge to the HPSI pump suction piping. With this alignment, an RHR pump serving as a booster pump to a HPSI pump, high pressure coolant can be injected into the RCS from the containment sump. To accomplish this alignment, the Refueling Water Storage Tank (RWST) must be isolated at the

, HPSI pump suction and also by adding redundant isolation valves in the HPSI J minimum flow recirculation line to prevent potentially contaminated sump water f from entering the vented RWST. A path from the RHR pump discharge to the HPSI must also be established. In addition, to assure adequate net positive suction head for th- HPSI pumps, sufficient downstream piping resistance must also be available. Appropriate measures to accomplish each of these conditions, consistent with single failure requirements, have been determined. A detailed description of these measures is set forth in Attachment 1.

As described in Attachment 1, installation of new equipment and modification of existing equipment is scheduled to be completed by the end of the Cycle 14 refueling outage, scheduled to commence in July 1987. There are no unused, safety-related motor control center (MCC) compartments presently available at Haddam Neck. However, with the installation of the new switchgear room, to be completed by the end of the Cycle L5 putage, additional safety-related MCC compartments will become available.(10) Until that time, sufficient redundant o safety-related circuits are not available. Accordingly, CYAPCO requests an extension of the present exemption with respect to the installation of electrical modifications until the end of the Cycle 15 outage. As demonstrated below, good cause exists for this extension.

ALARA IMPLICATIONS

-The currently projected occupational exposure requirement to install the proposed modifications is 130 man-rem. Hopefully, through effective ALARA planning, this can be reduced to less than 100 man-rem. However, due to the extensive work effort required in high radiation areas, a most optimistic estimate would still exceed 50 man-rem.

Since the accidents for which this modification is required do not involve containment failure, the probabilistic dose savings to the public are insignificant 4

i (9) CYAPCO considered modifications of existing piping systems to be superior to development and installation of a wholly new high pressure injection system. In addition to the obvious time involved in such an undertaking, a new system would present an additional probability of new breaks including large break LOCAs that would need to be assessed.

(10) For a description of the switchgear room, and the related history of its development and acceptance by the NRC, see H.R. Denton letter to L

3.F. Opeka, dated August 25,1986, " Fire Protection Exemption - Haddam Neck Plant."

compared to this installation dose. . Hence, if one equates health and safety to occupational radiation exposure, albeit within regulatory limits, the modification, in fact, results in a net detriment to public health and safety. This

.is by no means the only decision criterion, but we are calling to your attention the fact that, on the surface, this project is not attractive from a net man-rem perspective.

REQUEST FOR EXTENSION On April 28, 1986, the NRC granted, pursuant to 10 CFR 50.12(a)(2)(v), a temporary exemption from the single failure requirements of General Design Criterion 35 (10 CFR Part 50, Appendix A) and the Interim Acceptance Criteria for two valves (SI-MOV-24 and RH-MOV-784), both outside containment. ; As .

described previously, these valves did not satisfy single failure requirements, and required manual operation in the event prescribed conditions evidencing a certain range of SB LOCAs were to occur. The NRC requested that CYAPCO describe by September 1986 the long-term resolution,' and schedule for completion, of permanent plant modifications. . The NRC limited the term of the exemption to the end of the Cycle 14 outage, allowing that the term of the exemption may be extended for good cause shown. CYAPCO demonstrates below that good cause exists for the requested extension.

Scope and Duration of Extension CYAPCO intends to complete all modifications to mechanical equipment during by the end of the Cycle 14 refueling outage. These modifications, described in Attachment 1, include installation of new valves, piping, pipe supports and testing. With- these modifications, .the configuration to be employed in responding to' the subject SB LOCAs will satisfy the single failure requirements.

However, for the reasons described below, electrical modifications may not be practically accomplished until completion of the new Haddam Neck switchgear room.(ll) valves Thus,containment outside pending completion of the switchgear will be achieved room,(operation of 6 new manually.12) Accordingly, CYAPCO requests that the existing, temporary exemption to the single failure requirements be extended in one respect through the Cycle 15 outage to permit performance of necessary electrical modifications.

The requested limited exemption is extremely narrow in scope in that the only remaining task is to make manually operable valves remotely operable.

Following the Cycle 14 modifications, the entire ECCS will be single failure proof from an injection capability standpoint. The need for the limited exemption stems from the- very conservative, nonmechanistic assumption that severe fuel failures occur early in the accident and prohibit manual access to manipulate the new MOVs. Hence, CYAPCO is compelled to seek this limited exemption because of built in conservatism'in the regulations, not because of a defect in the proposal using mechanistic evaluation techniques.

(11) In its request for a limited exemption, CYAPCO indicated its desire to implement a permanent resolution prior to Cycle 15 operation. However, in that CYAPCO was uncertain as to the nature of the permanent resolution to be selected, no commitment was made as to timing (Reference (1) at page 6).

(12) High pressure sump recirculation is a single train operation and with the other train as a backup, only three of the six new valves have to be moved.

Continued Validity of Bases for Exemption The bases originally presented by CYAPCO in support of issuance of the temporary exemption, set forth in References (1) and (2) and as approved in Reference (3), remain valid and provide ample justification for extending the exemption. CYAPCO reiterates those bases here only briefly, but adopts the same by reference. To the extent additional information now exists which provides further support for the limited exemption, CYAPCO describes that information below. In these circumstances, CYAPCO submits that, and for reasons set forth below, the exemption remains authorized by law, provides adequate protection of the public health and safety and is consistent with the common defense and security.

Regulatory Provisions As described in Reference (1), and approved in Reference (3), whether the exemption is framed as applying to the single failure criterion set forth in GDC 35 or the provisions in the Interim Acceptance Criteria (IAC), a temporary exemption from single failure requirements is appropriate for the requested activity.

No Undue Risk to Public Health and Safety As presented in Reference (1), the exemption is consistent not only with the intent of the IAC and single failure requirements, but is consistent with the goals of the ISAP. Further, as described in Attachment 1, the configuration as to which the present extension is requested provides a slight increase in the level of protection to the public health and safety beyond the increase produced by the measures on which the exemption is presently based.

Regulatory Purposes Served As previously demonstrated in Reference (1), authorizing appropriate utilization of new technology applicable to ECCS performance, as has occurred in this instance with the application of the state-of-the-art analytical techniques employed in the Haddam Neck Probabilistic Safety Study, furthers the Commission's stated intentions at the time ECCS criteria were adopted. In addition, this limited exemption continues to be consistent with the intent of the ISAP regarding the granting of exemptions, identification of the most effective means of resolution, and establishment of an implementation schedule.

Special Circumstances As demonstrated in Reference (1), and approved by the NRC in Reference (3),

special circumstances, as defined by 10CFR50.12(a)(2), exist for permitting the exemption to allow temporary use of the HPSI pumps in the recirculation mode, even where that configuration temporarily does not meet the single failure requirements. Those special circumstances include both a net benefit to plant safety and, therefore, public health and safety (10CFR50.12(a)(2)(iv)), and that the exemption is temporary and CYAPCO has made good faith efforts to comply with the regulations (10CFR50.12(a)(2)(v)).

Benefit of the public health and safety As discussed in Reference (1), one measure of benefit to the public health and safety is whether the proposal results in an overall reduction in the probability of adverse consequences from reactor operation that could affcct the public health

.g.

and safety. In this situation, the original high head recirculation mode using s

charging pumps was found to be deficient for a narrow' spectrum of breaks, whereas the safety benefits derived from utilizing the HPSI pumps represent a credit for a much broader range of postulated breaks, measurably decreasing the overall core melt frequency (CMF) associated with small and medium break LOCAs at Haddam Neck.

CYAPCO originally calculated that a 27% reduction in Haddam Neck CMF for small and medium break LOCAs resulted from the implementation of the previously-approved interim measures. CYAPCO has determined that CMF will remain relatively unchanged following implementation of the above-described permanent modification, even without electrical control of the valves. When electrical contro)l3)is ultimately provided, an additional 5.4% reduction in CMF will be achieved.i Temporary Relief / Good Faith Efforts i

As noted above, the only relief CYAPCC seeks herein is temporary. CYAPCO requests that it be permitted to postpone full implementation of the permanent response to this range of breaks for one additional fuel cycle. The necessary mechanical modifications will be accomplished in the time frame in which CYAPCO previously indicated its desire to complete the modification. Thus, full redundancy of valves (albeit manually operated) will be provided during the next outage. Only electrical modifications are within the scope of this request, and those will be completed as promptly as practical, consistent with other CYAPCO commitments.

CYAPCO previously described its good faith efforts to respond promptly to the discovery of the unaddressed range of SB LOCAs. Indeed, the Staff concluded in this regard that "CYAPCO has been expeditious in its efforts to satisfy the i

ECCS requirements, including the IAC. Further, the licensee has shown good faith in rectifying the problem and in attempting to comply with the Commission's regulations as promptly as practicable." (Reference (3))

Since the exemption was granted, CYAPCO has made additional good faith efforts to identify and implement as promptly as practicable appropriate permanent measures to respond to the subject SB LOCAs.

Indeed, CYAPCO has diligently pursued a permanent resolution of this matter since the temporary exemption was granted. As described above, since the exemption was granted, CYAPCO performed extensive additional analyses to evaluate several potential options to identify the best permanent response to this condition. Eighty hours of computer analyses, using the latest available analytical methods (14) were dedicated to this effort. CYAPCO believes that the (13) As indicated in Reference (1), the above probabilistic evaluations examined only small and medium break LOCAs. Additional benefits would be attained from use of the HPSI pump recirculation mode following a consequential LOCA. CYAPCO did not calculate those precise reductions, but notes their existence.

(14) The computer models utilized by CYAPCO in performing these analyses are those employed in the Haddam Neck Probabilistic Safety Study. These are described in Reference (1).

_9_

permanent response ultimately decided upon provides the best practical option for responding to this range of SB LOCAs. When fully implemented, this option provides the highest level of assurance that these breaks can be properly addressed. It is important to note that although one or more options might have been capable of simply of morethe satisfying quickly providing limitations of an adequaterequirements,tl5 applicable response frorp tpethe standpoint solution decided upon provides the best overall reduction in risk in the most practical manner. Thus, although full implementation will require extending the exemption, in part, for an additional fuel cycle, both from a regulatory and public health and safety standpoint, the overall benefits from the proposed permanent modification is greater than any of the other practical options considered.

Further, good cause exists for the length of the requested extension. CYAPCO will implement all necessary mechanical modifications during the Cycle 14 outage. These modifications include installation and testing of new valves, piping and supports.(16) Appropriate revisions to emergency operating procedures, including training thereto, also will be accomplished prior to Cycle 15 operation. Similarly, modifications to technical specifications regarding surveillance of the new valves and RCS leakage will be made and submitted to the NRC in ample time for the start of Cycle 15. The actions for which the extension is necessary involve electrical modifications. Presently, there are no unused, safety-related motor control center (MCC) compartments available at Haddam Neck. However, with the installation of the new switchgear room, to be completed during the Cycle 15 outage, additional safety-related MCC compartments will become available. Until that time, sufficient redundant safety-related circuits are not available.

As described below, CYAPCO considered a temporary modification to accomplish power operation of these valves prior to the Cycle 15 outage. The cost associated with " Jerry Rigging" a power supply from a safety related (15) For instance, the loop fill header option may not have strictly satisfied the core temperature limitations of the IAC for the case wherein one of the injection lines is completely severed. However, for all other break locations there remained some potential for core uncovery (even though maintaining acceptable fuel cladding temperatures from a regulatory compliance standpdnt). Consequently, CYAPCO did not consider this option to be desirabic as a primary response mechanism even when equipment necessary to implement this option was available and installation thereof could have been completed sooner than the HPSI recirculation option.

(16) CYAPCO is procuring some of the necessary valves from other utilities.

These valves, originally intended to be used in now-cancelled facilities, were originally procured as safety grade and are expected to satisfy all applicable seismic and environmental requirements. However, CYAPCO has not yet received those valves. In the event the valves from the other utilities are damaged, or otherwise turn out to be unacceptable, CYAPCO could be forced to obtain the valves from several different manufacturers (of those contacted, none could provide all tha valves to support Cycle 14 implementation). The procurement process would be lengthy, extending perhaps as much as 40 weeks. If this should occur, CYAPCO will, of course, inform the NRC promptly.

< MCC during 'the 1987 refueling outage would exceed $500',000. The temporary modification would also require an exemption from the single failure criteria, as MCC 3 is the only MCC where emergency power will be available until the new switchgear room is completed. Consequently, Haddam Neck would be swapping mechanical single failure problems with electrical single failure problems for one cycle of operation. It is very important that this work is done right the first time to preclude the potential for adverse effects from an undesirable configura-tion. Interim modifications would also have an undesirable effect on operator training in that the operating procedures would only be valid for one cycle until the permanent modifications were completed. Current congestion in the control.

room would complicate our ability to install a humanly engineered arrangement in the control room for the contemplated interim instrumentation and controls.

This congestion will be alleviated in part by 1989 as a result of major (a total budget of $21 million has been allocated) modifications to the Reactor Protection System. Hence, the planned modification schedule would enable us to optimize the final configuration in the control room, and would be synchronized with our Control Room Design Review efforts. In summary, the best conceivable interim approach still would not satisfy single failure requirements, would be extremely expensive, would require additional occupational exposure to install and then remove, and would be interim in nature. Our proposal to remedy this issue is synchronized with other major planned modifications. For these reasons, good cause exists for extending the subject exemption until the conclusion of the l Cycle 15 outage.

Summary The decision-making process regarding the selection of a permanent means to resolve this matter has been both comprehensive and complex. The merits of any specific option considered were constantly balanced against the undesirable features or drawbacks associated with those options. Throughout our evaluation process, the overriding concern has been a selection of the best means to protect the public health and safety, with due consideration to both the letter and spirit of regulatory requirements and the fundamental principle of defense-in-depth.

The option we propose herein will result in compliance with all regulatory requirements at the earliest reasonable schedule. This is the only option presently known to achieve this result. Further, it is in full accord with the defense-in-depth principle,-in that the ECCS will be redundant and diverse and the single failure criterion will be satisfied. This decision was made even though it is unattractive from the standpoint of man-rem and dollar expenditures, the former being of prime importance. ALARA initiatives are and will remain an extremely high corporate priority. Indeed, CYAPCO is undertaking numerous initiatives designed to improve our man-rem performance in all facets of our operation. Thus, in this particular instance, CYAPCO carefully considered the fact that between 50 and 130 man-rem could have been avoided by seeking a permanent exemption from the single failure criterion. In addition, approxi-mately $3 million in implementation costs could have been similarly avoided.

Nonetheless, our ultimate decision reflects the fact that factors such as the defense-in-depth principle, conformance to regulatory requirements, and the importance of a single failure proof ECCS take preference over a pure man-rem comparison given the circumstances associated with this decision. We are hopeful that the Staf f recognizes that projects such as this one drive up our man-rem expenditures, but we should not be penalized for such actions because they represent the right thing to do.

We amplify the above discussion by noting that a variety of changed circum-stances ..could have resulted in a different conclusion from CYAPCO. For exampic, if the applicable regulatory criteria were contained in guidance documents rather than requirements, or if our calculat2d core melt frequency were currently less than our corporate safety goal, then the project at issue here may not have been proposed.

In summary, the planned course of action represents the best available alterna-tive and the one we are committed to pursue. Again, since it is unattractive from a man-rem and dollar standpoint, we are .very desirous of identifying a more cost-effective solution. Given these circumstances, we are compelled to continue our pursuit of a more attractive solution. At a minimum, CYAPCO will continue to review the implementation details carefully to limit occupational exposures consistent with ALARA considerations. Further, CYAPCO ~ also intends to continue its pursuit of other options not presently identified which could achieve the same or nearly the same public health and safety benefit with substantially reduced man-rem and dollar costs. In any event, protection of public health and safety and compliance with applicable regulatory requirements will remain the dominant decision parameters. CYAPCO will continue to keep the NRC apprised of any developments in this regard.

CONCLUSION For the above reasons, the Staff should grant this request for an extension of the exemption from single failure requirements. CYAPCO is, of course, prepared to meet with the Staff at its convenience to discuss this request as necessary.

Pursuant to 10 CFR 170.21, CYAPCO encloses herewith a check for $150.00 as the application fee for processing this request.

Very truly yours, CONNECTICUT YANKEE ATOMIC POWER COMPANY AECA

3. FM3 eka v Senior Vice President

i Attachment 1 HADDAM NECK PLANT PROBABILISTIC SAFETY STUDY LOCA ANALYSES PERMANENT SMALL BREAK LOCA RESPONSE MEASURES INTRODUCTION In conjunction with the Integrated Safety Assessment Program (ISAP) for the Haddam Neck Plant, Connecticut Yankee Atomic Power Company (CYAPCO) performed a Probabilistic Safety Study (PSS) which included best estimate LOCA analyses for that facility. Through these analyses, CYAPCO identified a small range of break sizes in one loop of the reactor coolant system (RCS) for which safety injection flow in the high pressure recirculation mode may be insufficient to provide adequate core cooling absent modification of facility operating procedures and/or system (eg, valve) re-alignments.

CYAPCO reported the identification of this potential condition to the NRC on March 25,1986, pursuant to 10 CFR 50.72. By letter dated April 22, 1986, CYAPCO presented an interim response to this condition and requested a temporary exemption from applicable single failure requirements. That exemption was issued by the NRC by [[letter::B11409, Responds to IE Bulletin 80-06, ESF Reset Control. Trip Signal to Containment Air Activity Pump & Containment Sump Pump Provided.Removal of Safety Injection Actuation Signals from RHR Valves Being Evaluated|letter dated April 28,1986]] (Reference (3)).

l Therein, refueling the NRG ) authorized outage.ll The NRCthe exemption stated until the endmodification that a permanent of the Cycleand 14 schedule for implementation should be submitted by September 1986, and that, for good cause shown, the exemption may be extended.

CYAPCO describes herein the modifications considered and that selected as a l permanent response, along with the schedule for implementation.

BACKGROUND In Attachment (1) to their April 22,1986 request for exemption, CYAPCO fully described the background related to the identification of the postulated range of SB LOCAs to which the measures requiring an exemption were designed to respond. CYAPCO incorporates that discussion herein by reference.

CYAPCO is now implementing certain modifications to the Haddam Neck l facility to provide a permanent means to respond to the range of SB LOCAs for which it was determined that prior NRC-approved analyses had not adequately addressed. These modifications include installation of new piping and valves to provide a mechanism for responding to those breaks which satisfies single failure requirements. Substantial electrical modifications will also be required.

CYAPCO intends to complete the required mechanical modifications during the Cycle 14 outage. The electrical modifications, however, cannot be completed until the Cycle }$ outage, simultaneous with the construction of the new Switchgear Room.t2) i (1) The Cycle 14 refueling outage is scheduled to run for 14 weeks, beginnin5 July 1987.

(2) The Cycle 15 refueling outage is scheduled to run for 10 weeks, commencing November 1988.

DISCUSSION POSTULATED TRANSIENTS

CYAPCO described the precise transients 'to which the modifications described below are directed in Attachment I to their April 22,1986, request for exemption. CYAPCO incorporates that discussion herein by reference.

j TRANSIENT RESPONSE: CYAPCO has evaluated various options for providing a permanent means of responding to the range of postulated SB LOCAs. Except as indicated below, CYAPCO's evaluation has employed detailed computer modelling and analyses in accordance with the methodology presented in the Haddam Neck Probabilistic Safety Study, submitted to the NRC on March 31, i 1986. CYAPCO describes below the principal options evaluated, and conclusions regarding subject SB each LOCAs. op(tion's

3) capacity to provide an appropriate response to the Loop 2 Cold Leg / Loop 4 Hot Leg: One option considered would involve simultaneous injection of coolant through the loop 2 cold leg and loop 4 hot leg.

To provide maximum flow and to satisfy single failure requirements, several modifications to the Charging System would be required. Figure 2, attached hereto,(4) option. illustrates the modifications that would be required to implement this First, to provide maximum flow, the existing charging flow control valves (FCV-110 and 110A) would need to be bypassed with full ported motor-operated gate valves to reduce the pressure drop. The flow control valves, even when fully open, are highly restricting. Further, to provide flow and redundant valves in the loop 4 hot leg, MOV-290 would be locked opened and two new parallel valves would be installed in series with MOV-290 in that line. These

valves would be locked closed at the discretion of the plant operators during normal operation. CYAPCO also considered upgrading flow transmitters FT-lilA and FT-IllB to full environmental and electrical qualification status to allow reliance on those transmitters to assess whether a break existed in either of the two injection lines. CYAPCO determined,' however, that the combined a flow paths would provide adequate core cooling except when the break is postulated to occur in one of those unisolated injection lines. Regardless of l which line the break is in, the remaining flow is unable to match Reactor

! Coolant System boil off until significant depressurization occurs. Accordingly,

CYAPCO decided against implementation of this option as a permanent response j mechanism.

J l

(3) The current response to these breaks, as to which the exemption from single failure requirements was sought in the first place, is procedurally addressed in the Haddam Neck Emergency Operating Procedure (EOP).

, That procedure prescribes conditions under which that alternative response i

to' inadequate core cooling is to be implemented. CYAPCO anticipates

! that the same conditions will be utilized to trigger application of the permanent measures described below. Appropriate revisions to the EOP to

, reflect new permanent measures will be completed prior to startup of

Cycle 15. The original recirculation method (use of RHR pumps to deliver containment sump water to the charging pumps) will continue to be used in all other instances.

(4) Figure 1, attached hereto, illustrates current ECCS recirculation lineups and is provided for reference.

1 i

Loop fill headers: CYAPCO also considered charging pump injection through the existing loop fill headers. This alternative involves the use of a single charging pump in series with a RHR pump to provide flow to each of the four loop fill valves. This flow path is illustrated in Figure 3. CYAPCO's analyses demonstrated that if the postulated initiating break is in one of these one and one-half Inch lines, the original injection scheme, b, high head recirculation using charging pumps, provides adequate core cooling. However, should the initiating break be in a location where this path would be relied upon, certain undesirable conditions may occur which convinced CyAPCO not to consider this option further as a permanent respcase mechanism.0) Specifically, to achieve injection through these lines, it is necessary to fill the suction legs of the cold leg piping between the steam generators and reactor coolant pumps. Although sufficient core cooling (with steam) is maintained to keep fuel cladding temperatures below the temperature limits established in the Interim Acceptance Criteria, cleared of injection therp)would be some core uncovery as the loop seal is water.t6 Pressurizer auxiliary spray: CYAPCO also explored, although detailed computer analysis were not performed, simultaneous injection through the loop 2 cold leg and the pressurizer auxiliary spray, using charging pumps. This option would have required the addition of at least one new valve (Figure 4) to satisfy single failure requirements. It was determined, nowever, that if the postulated break was in the loop 2 cold leg, the majority of the coolant would flow out the break.

Further, in that the auxiliary spray line is only one and one-half Inches in diameter, the total flow that could be provided is not substantially greater than would be available simply by injecting through the loop 2 cold leg. Accordingly, CYAPCO concluded that this option does not possess sufficient flexibility to warrant further consideration.

HPSI Realignment: The above options represent the best available options involving utilization of the charging pumps. In view of the results of the investigation, described above, CYAPCO determined that further consideration should be given to alignments em adopted as an interim solution.(7) ploying the HPSI pumps, such as was initially U) As a matter of prudency, CYAPCO intends to leave the description of this option as another available flow path in the EOP. It will remain only as an option, and is not intended, nor is it requested, that it be considered as a licensing basis response.

(6) In view of the results of the above-described analyses, CYAPCO did not pursue the extent to which the components and equipment in this flow path would require upgrading to satisfy seismic and/or environmental qualification requirements in order to serve as a licensing basis ECCS response mechanism.

(7) CYAPCO considers the modification of existing piping systems to be superior to options which would entallinstallation of substantial new piping and/or a wholly new high pressure injection system. In addition to the additional time involved in implementing such a modification, any new system would present the potential for new breaks, including large break LOCAs, that would need to be considered. Thus, irrespective of the obvious costs, CYAPCO views such options as undesirable from a regulatory and public health and safety standpoint.

This option provides for high pressure coolant injection by aligning the RHR pump discharge to the HPSI pump suction piping. This alignment provides for a RHR pump to act as a booster for a HPSI pump, permitting high pressure injection into the RCS from the containment sump. Several actions are required to fully implement this option. First, a means to isolate the Refueling Water Storage Tank (RWST) from the flow path is required to prevent potentially contaminated sump water from entering the vented RWST. Also, a flow path from the RHR pump discharge to the HPSI pump must be established. Further, to assure adequate net positive suction head for the HPSI pumps, sufficient downstream piping resistance must also be available. Appropriate measures to accomplish each of these conditions, consistent with single failure requirements, have been determined. These modifications are described more fully below, and are illustrated in Figure 5.

Isolation of the RWST will be accomplished by adding isolation valves (motor-operated) to the RWST piping at the HPSI pump suction and also by adding redundant isolation valves in the HPSI minimum flow recirculation line. These will prevent sump water from filling the tank during the recirculation mode.

These new valves will normally be open so as not to impair the initial HPSI injection from the RWST. The valves would be closed during the recirculation phase. Additional HPSI suction piping, and valves, will also be installed to provide redundant flow paths from the RHR pumps to the HPSI pumps. This piping will be located in the PAB pipe trench and HPSI/LPSI pit.

The capability to provide sufficient downstream piping resistance for the HPSI pumps will be provided by adding four throttle valves, one to each of the RCS loop injection lines. These valves will also be used, prior to implementation of this option, to balance the flow delivered through each of those paths. Flow balancing will be accomplished with temporary RHR flow indicators and will provide adequate assurance that HPSI pump run-out will not occur.

Transient Response Implementation:

Valves: CYAPCO has purchased the four required eight-inch motor-operated valves from Public Service Indiana (Marble Hill) and is purchasing two one-inch motor-operated valves from the Washington Public Power Supply System (WNP-

4) pending resolution of documentation deficiencies. These valves will be available for the end of the Cycle 14 refueling outage. CYAPCO is reasonably confident that the valves will be in satisfactory physical condition and that necessary valve qualification documentation will be obtained. In the event such documentation cannot be obtained, and other means of qualification cannot be accomplished, manufacturers. g. Y) TheAPCO could valves be forced in each of thetoinjection purchase valves lines, directly from are in containment, the manual globe valves to be set prior to operation and can be obtained from valve manufacturers with a reasonable lead time.

(8) CYAPCO has determined that such purchases would most likely have to be accomplished from more than one manufacturer because none of the manuf acturers contacted could provide all the required valves. Also, the necessary steps in the procurement process would entail a lead time of at least 40 weeks. If this were to occur, the valves may not be available for installation during the Cycle 14 refueling outage.

Piping: The cross-tie connection between the RHR pump discharge and the HPSI pump suction will be accomplished by the addition of two eight inch lines, each with a separate motor-operated valve. Modifications to the HPSI suction piping will be located in the PAB pipe trench and HPSI/LPSI pit. Modifications to the HPSI miniflow line will be in the HPSI/LPSI pit. Modifications to the four injection lines for flow balancing will be in containment. The tie-in to the RHR system will require that the RHR system be drained and disabled and will require a full core offload. This offload is already planned for the Cycle 14 outage to support the 10-year core barrel inspection. Consequently, CYAPCO should be able to complete all piping and valve modifications during the Cycle 14 outage.

Assuming availability of qualified valves, manual operation of this alignment can be accomplished.

Electrical: The pacing item for full implementation of the above modifications is the availability of power supplies for the new MOVs. Presently, there are no safety-related motor control center (MCC) compartments available at the Haddam Neck Plant. However, a limited number of MCC-5 compartments will become available upon completion of the new switchgear room, by the end of the Cycle 15 outage.(91 No temporary safety-related power supplies are available that would satisfy single failure requirements. Accordingly, CYAPCO intends to power three of the MOVs from the safety bus in the new switchgear room and power the remaining MOVs from the old switchgear room. These modifications, along with the work on the new switchgear room, will be accomplished by the end of the Cycle 15 outage.

Procedures / Training: New procedures and appropriate training will be implemented to assure that the new valves outside containment can be manually operated when required. CYAPCO has determined that there will be adequate manpower, access and time to implement these operations. Further, CYAPCO intends to conduct periodic surveillance of the valves pending completion of the electrical modifications during Cycle 15 outage. Proposed Technical Specification changes for valve surveillance will be submitted to the NRC to support conduct of the surveillance during Cycle 14.

RISK REDUCTION:

Using the methodology described in the Haddam Neck PSS, CYAPCO has determined the frequency of breaks at issue here and the associated decrease in Core Melt Frequency (CMF) for small and medium break LOCAs which results from use of the HPSI pump alignment with the RHR pumps for high pressure recirculation. CYAPCO previously described their conclusions regarding such modifications in Attachment I to their April 22,1986, letter. With respect to the above described permanent modifications, CYAPCO had calculated the (9) The new Switchgear Room will be located immediately north of the Primary Auxiliary Building and adjacent to the Waste Disposal Building.

This building will be classified as quality Category 1. Special cable runs will be installed in the PAB and into containment. The building will house a new safety-related 1500/2000 KVA XFMR-480 volt load center which will feed a new safety-related 480 volt motor control center. A complete description of the building and the schedule for completion is set forth in H.R. Denton's letter to 3.F. Opeka, dated August 25,1986, " Fire Protection Exemption - Haddam Neck Plant."

additional reduction in CMF achieved by installation of equipment and components that satisfy the single failure requirements. In addition to the previously calculated 27% reduction from using the HPSI alignment even when not single failure proof, a further reduction of the CMF for small and medium breaks of 5.4% will be realized upon full implementation of the permanent modifications.

HADDAM NECK -

ECCS RECIRCULATION LINEUPS O BASELINE ,Npq .

SI-FCV-875  ;

l RWST l-----M--

r------

SI-MOV-24 SI-V-857A hph+

___L_

_______{(__ g $

@ l  !  ! j !N-co-CONTAINMENT SUMP .

,r--pd lRH-MOV-874 l

HPSI PUMPS

,,,,,j lN SI-V-8578 l l

g l

l____ lJQ pg l

l RH-MOV-22 l RH-MOV-33A CH-FCV-110

$ ( RHR $

h Nb

) '

, PUMPS I

CHARGING l REGEN HX'S A RHR [ ~

b " '

CH-FCV-110A u

6 RH-MOV-33B OPEN RH-RCV-796

)

LO RH-RCV-602 rf l _RH-MOV-344 l CH-MOV-292B FROM LPSI y y

'/

RH-MOV-295 CH-MOV-292C 1 J V $ ~ h

-N DG s P -

B ______ ___T TO LO P 2 CL "o""^' ""a N

-N DG s ,, ,, ,, ,,

< c RCS - LOOP FILL TO LOOP 2 CL 1

FIGURE 1

HADDAM NECK -

ECCS RECIRCULATION LINEUP LOOP 2 CL AND LOOP 4 HL .

CONTAINMENT SUMP .

TO LOOP FILL RH-MOV-22 RH-MOV-33A CH-FCV-110

[ RHR S f

)b Nb REGEN A HR @ U U -M- (

6 RH-MOV-33B CH-FCV-110A La RH-RCV-796

) RH-RCV-602 g LO NEW CH-MOV-2928 FROM LPSI y y NEW CH-MOV-292C V h

-N DG s 7 -

v b CH-MOV-292A TO LOOP 2 CL h

• w M LO NORMAL RHR

%' ( $ CH-MOV-290

< c s

TO LOOP 4 HL TO LOOP 2 CL FIGURE 2

HADDAM NECK -

ECCS RECIRCULATION LINEUP LOOP FILL HEADER ,

i l'

I i

CONTAINMENT i SUMP f'

RH-MOV-22 RH-MOV-33A b [ ~

RHR b

)@ "

y% ) ) A ING

, PUMPS CHARGING b

d[

~

A HR

-Oc- f u

M RH-MOV-338 OPEN] [

RH-RCV-796

) LO -

RH-R

-602 f RH-MOV-344 FROM LPSI A

'/

RH-MOV-295 V h n .

-N DC s 7-3 TO LOOP 2 CL -* w M N NORMAL RHR h' )( --

RCS - LOOP FILL FIGURE 3

HADDAM NECK -

ECCS RECIRCULATION LINEUP LOOP 2 CL AND PZR SPRAY ,

l i

I CONTAINMENT SUMP l ,

i RH-MOV-22 e ~

RH-MOV-33A CH-FCV-110

[ ~

RHR $

)g HX'S (

f

) )

RHR -

CHARGING REGEN HX'S l FROM LOOP 1 HL NORMAL RHR 7' %3 ( -

PUMPS 6 RH 0 38 LC La RH-RCV-796 F'

) RH-RCV-602 ' '

LC LO CH-MOV-290 CH-MOV-2928 FROM LPSI ( @

$ TO LOOP 4 HL CH-MOV-292C

)A V h NEW hd d

~

v $ DG

@ o CH-MOV-289 M *LO

} TO LOOP 2 CL -+ w NORMAL RHR

_'N q g O PZR

( ,

e TO LOOP 2 CL FIGURE 4

HADDAM NECK g .

ECCS RECIRCULATION LINEUP Nga _

NEW HPSI MODIFICATION @NECg , ,

lRWST @ @

Ill Ill NEW SI-MOV-24 M SI-V-857AX -Mh (I) b b g NEW

~

NEW l

CONTAINMENT SUMP l---yk--- HPSI PUMPS SI-V-857B g

RH-MOV-874 M [I 1 NEW U ,i TMb-

. I i

RH-MOV-22  ! I b

) )

DG-N- d[

P S RHR "rS a

j (2)

[j I

FROM LOOP 1 HL NORMAL RHR

" Ep

' [ ~ ) ) l TO CHARGING (2) ll SYSTEM g, b

l La RH-RCV-796 g

) RH-R

-602 rf LO FROM LPSI l

• I

'/ I g

L-- -

V b

• NOTES:

1.OPEN DURING INJECTION PHASE, M' hd--

• g CLOSED DURING RECIRCULATION PHASE.

1 V

3 w

2. CLOSED DURING INJECTION PHASE, OPEN DURING RECIRCULATION PHASE.

TO LOOP 2 CL --** w 3. THROTTLED TO BALANCE l

O W AL RHR M hQ

• 4. - INDICATES NEW HPSI SUCTION PIPING l FIGURE 5 1