Text

Forwards Comments on NRC Topic Evaluations,Draft & Final Integrated Safety Assessment Repts (Isar),App D to Isar & Integrated Implementation Schedule.Util Strongly Supports Continued Development of Program
	ML20236M939
Person / Time
Site:	Millstone
Issue date:	08/04/1987
From:	Mroczka E; NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:	; NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
	A06501, A6501, B12529, NUDOCS 8708110304
	Download: ML20236M939 (51)
	v • d • e

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A06501 B12529

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l Re: Integrated Safety Assessment Program U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555 Gentlemen:

Millstone Nuclear Power Station, Unit No.1 Integrated Safety Assessment Program (ISAP)

By letter dated July 31, 1986,(1) Northeast Nuclear Energy Company (NNECO) submitted a comprehensive report on the Millstone Unit No.1 ISAP. This report reflected several years of activities with the NRC on the development and implementation of a pilot program to assess and prioritize pending plant modifications and licensing issues for Millstone Unit No.1.

The report included summaries of the status and scope of all of the topics included in the Millstone Unit No.1 ISAP, as well as detailed discussions of additional broad-based licensee and regt;latory issues. In addition, the prioritization process which NNECO has developed to assess the Millstone Unit No.1 ISAP topics was described and a summary of the results of NNECO's assessment and ranking of each topic with a well-defined scope was provided.

NNECO also stated its intention to utilize the results of the ISAP prioritization in the development of an Integrated Implementation Schedule (IIS) for Millstone Unit No.1.

On April 2, 1987,(2) the NRC Staff issued for comment draf t NUREG-Il84, the Integrated Safety Assessment Report for Aillstone Unit No.1. In the rcport, the NRC documented its review of the Millstone Unit No.1 ISAP. Specifically, the NRC recounted its review of NNECO's topic evaluations and prioritization, the Millstone Unit No.1 Probabilistic Safety Study (PSS), and the Millstone Unit No.1 Operating Experience Review. In addition, the NRC proposed several additional areas for NNECO to consider for further evaluation. These areas included severe accidents, reliability engineering initiatives, treatment of external events, and station blackout..

(I) 3. F. Opeka letter to C. I. Grimes, " Integrated Safety Assessment Progr m - Final Report for Millstone Unit No.1," dated July 31,1986.

(2) C. O. Thomas letter to E. 3. Mroczka, " Millstone Nuclear Power Station, k Unit No.1 - Draf t Integrated Safety Assessment Report (NUREG-ll84)," 0 0

dated April 2,1987. \

9708110304 B70004 PDR ADOCK 05000245 P PDR

U.S. Nuclear Regulatory Commission B12529/Page 2 August 4,1987 Subsequently, on June 16 - 19, 1987 NNECO and the NRC met to discuss the draft NUREG-Il84 and NNECO's activities on the development and submittal of an IIS for Millstone Unit No.1. In addition, NNECO and the NRC Staff met with the Advisory Committee on Reactor Safeguards on July 7 and 9,1987 to discuss the ISAP.

NNECO has recently completed its review of the draft NUREG-Il84, and its comments are provided herein. Comments on the NRC's review of the Millstone Unit SS and Operating Experience Review were previously sent to the Attachment A provides NNECO's discussion on the scope, evaluation and prioritization of each topic. In addition, in Attachment A NNECO provides its recommended resolution and schedular status of each ISAP topic.

In Attachment B, NNECO provides other clarifications and information to allow NUREG-Il84 to more accurately reflect the technical aspects of each individual ISAP topic.

Attachment C provides NNECO's comments on Appendix D of the Staff's draf t NUREG-Il84, pertaining to the Staff's recommendations for additional evaluations and integ;ation of selected ISAP topics.

Finally, in Attachment D, NNECO provides the NRC with our proposed 115 for Millstone Unit No.1. This includes discussions of the process which NNECO used to develop the 115, including the various constraints which were factored into the development of the !!S.

NNECO is very enthusiastic about the results of the ISAP to date. An important element of the ISAP is that each topic is evaluated, regardless of its origin (e.g., licennee, NRC or INPO) against the same set of criteria. These criteria, contained in the Analytical Ranking Methodology (ARM), represent a valuable tool for decision making.

By use of the ARM, NNECO combines probabilistic and deterministic reviews of potential public health and safety impacts of proposed projects with assessments of potential impacts on personnel safety, plant economic performance and personnel productivity. The ARM also provides conversion and weighting factors to integrate the four attribute scores for each ISAP topic into one composite score. Thus, the ARM considers all significant attribute impacts of proposed projects and studies, assuring that topics with the greatest potential benefits are assigned highest priority.

(3) 3. F. Opeka letter to C.1. Grimes," Comments on NRC Review of Millstone Unit No.1 Probabilistic Safety Study and ISAP Topics," dated October 21, 1985.

(4) 3. F. Opeka letter to C. I. Grimes, "NRC Final Report on PRA Review of ISAP issues," dated March 26,1986.

(5) 3. F. Opeka letter te C. I. Grimes, ' Comments on ISAP Review of Operating Experience," dated October 3,1985.

U.S. Nuclear Regulatory Commission B12529/Page 3 ;

August 4,1987 j l

However, the ARM rankings are only one input into the development of an IIS. ;

Many other so called "real world" constraints need to be factored into the "

development of an IIS. For example, NNECO is striving to significantly reduce ,

the occupational exposures at Millstone Unit No. I as part of the ALARA I improvement program. Thus, a major consideration in the development of an IIS is the occupational exposure costs associated with the installation of many of the ISAP projects. For example, if a project will provide a reduction in the probability of an accident of 1 x 10-5 that would result in a public exposure of 106 man-rem, a probabilistic savings of 10 man-rem is invelved. However, the project may requ;re 50 man-rem to install. If one considers such consequences on an equal basis (6)(i.e., exposure to a worker is equal to exposure to the public),

then a decision to not implement the project would result in a net savings of 40 man-rem. This is a factor that cannot go unnoticed in the development of an .

IIS. ;

In ISAP, NNECO has included installation exposure as one decision input for the 115. We recommend that the NRC give serhus consideration to this factor in reviewing NNECO's proposed IIS as well as in a re-review of the NRC's proposed prioritization ranking.

Occupational exposure is just one of the factors NNECO considers in the development of the IIS. Other factors, such as resources required (both manpower and costs), regional power needs and outage durations, external impacts (e.g., regulatory concerns), and equipment and material availability are also considered.

This should not be construed to mean that NNECO is allowing public safety, or even the ISAP ranking, to take a backseat relative to the above mentioned constraints. NNECO has historically placed a high emphasis on public safety throughout its entire nuclear program. Interna! corporate safety goals are in place, against which the current status of each of NNECO's operating nuclear power plants are regularly compared. Towards this end, NNECO has a Living Probabilistic Risk Assessment (PRA) Program in place to complete Level 3 PRAs on each of its nuclear power plants over the next several years. Millstone Unit No I currently has a Level 1 PRA; activities aimed toward expanding the scope to Level 3 are scheduled to begin during the latter part of 1987.

It is our belief that the public health and safety is not being compromised by considering the above noted scheduling constraints. Specifically, we believe that the ISAP, including our methodology for developing the 115, provide the necessary tools to best accomplish all of the above objectives. Further discussion of the process used to develop the Millstone Unit No.1 IIS is provided in Attachment D.

With respect to the formalization of the Millstone Unit No.1 IIS, NNECO offers the following preliminary thoughts to the NRC. Historically, the scheduling of projects has been an iterative process whereby NNECO and the NRC Staff would negotiate and agree on a schedule for implementation of NRC-mandated j (6) NUREG/CR-3665 " Optimization of Public and Occupational Radiation j

Protection at Nuclear Power Plants, A Calculational Method, Volume 3" September 1,1984.

U.S. Nuclear Regulatory Commission j

j. B12529/Page 4 ' j August 4,1987 ;

i' projects. This process, although allowing limited flexibility in the scheduling of NRC-mandated activities, many times forced NNECO to defer implementation of projects which we thought to be valuable to the plant in order to address NRC concerns of less safety benefit. Specific exemples include seismic hanger upgrades, selected Appendix R fire protection modifications, and several modifications resulting from the NRC response to the Three Mile Island Unit No. 2 accident. We are not implying that these modifications provided no i' benefit to the plant; rather, we believe we could have better addressed NRC and NNECO concerns in a systematic manner that would have provided the most overall benefit to the plant.

In light of the above, NNECO believes therv must be recognition by the NRC of the value of utility-initiated projects and that these projects must be weighed on the same scale in comparisons with NRC-mandated projects. In this manner, the IIS should reflect a schedule which best addresses the overall needs of the plant and which will allow the plant to continue operating in a safe and efficient manner. Our experience with the NRC in the pilot ISAP to date is very encouraging in this area.

One important element of ISAP has always been a threshold concept, such that issues shown in the integrated assessment to be of Ne or no benefit can be deferred or dropped. in this report, as outlined in Attachment A, NNECO is proposing to defer or drop a number of ISAP topics, both NNECO and NRC-initiated. As such, we urge the Staff to carefully consider and evaluate the information previously provided in the ISAP report and the additional information provided in Attachments A and D to this letter.

Another facet of the IIS is that it must be a dynamic schedule, readily amenable to update and change. That is, as new issues arise, either utility or NRC-initiated, the schedule must be able to be updated to reflect an appropriate schedular priority for these new issues. As previously discussed, scheduling of new issues will reflect consideration of several factors, including, for example, the ARM ranking.

NNECO does not believe that the 115 should be formalized in a license i amendment which would contain specific implementation dates for each project identified. ' A license amendment of this kind would require a license amendment change each time a project is to be adied or deleted from the schedule. As such, the schedule would tend to be ovet restrictive and cumbersome for both the NRC and NNECO. This would make the IIS a static, rather than dynamic schedule, in addition, this format weuld preclude scheduling in the 115 of more broad-based, less well-defined activities and more general level of effort licensing activities.

NNECO is currently evaluating other options available for formalization of the IIS, including less restrictive license amendments. This evaluation is currently being conducted in conjunction with other NNECO activities to formalize the ISAP and IIS process in-house. It is envisioned that the format for regulatory formalization of the Millstone Unit No.1 IIS could rely upon, and refer to, a formal process for scheduling both projects and studies. This process would be maintained as a formal NNECO document and would be referenced in an amendment to the Millstone Unit No. I license. The process would expand on the

U.S. Nuclear Regulatory Commission B12529/Page 5 August 4,1987 planning and scheduling philosophy described in Attachment D and would serve as the basis for scheduling activities related to Millstone Unit No.1. In fact, most of the methodology associated with this process has previously been provided to the NRC. This approach will allow NNECO and the NRC the flexibility to schedule work in a timely and consistent manner. We envision sharing the bases of our decisions with the NRC on a timely basis, even though we do not intend to process a license amendment each time a schedule change is made. As such, we will continue to work with the Staff towards development of a formal license amendment as part of the conclusion of the pilot ISAP program and would welcome the Staff's concurrence on our philosophy towards scheduling projects, as outlined in Attachment D.

Finally, we would like to emphasize that our experiences to date with the ISAP have demonstrated the program to be a resource-efficient and cost-effective process for enhancing nuclear power plant safety and operation. For this reason, NNECO strongly supports continued development of the program and the methodology by continuation of the ISAP appr ach to addressing issues. In

. addition, we reiterate our desire to formally expand this program to Millstone Unit Nos. 2 and 3. In this vein, we would be glad to meet with you to further discuss the ISAP.

Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY k/Afr E. T.oczka //

d Senior Vice President cc: W. T. Russell, Region 1 Administrator M. l.. Boyle, NRC Project Manager, Millstone Unit No.1 T. Rebelowski, Resident inspector, Millstone Unit Nos. I and 2 D. H. Jaffe, NRC Project Manager, Millstone Unit No. 2 R. L. Ferguson, NRC Project Manager, Millstone Unit No. 3 W. 3. Raymond, Resident Inspector, Millstone Unit No. 3 l

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Attachment A B12529/Page1 Attachment A Comments on NRC Staff's Topic Evaluations Topic 1.01 - Gas Turbine Generator Start Logic Modifications ISAP Topic No.1.01 concerns the protective trips utilized on the emergency gas turbine generator (GTG). NNECO's evaluation of this topic focused on bypassing the GTG protective trips that are not presently bypassed during emergency operation. These trips are: a) the light-off speed and generator excitation trips; b) the high lube oil temperature trip; and c) five GTG output breaker protective trips. The high lube oil temperature trip is now bypassed during emergency operation.

NNECO's ISAP assessment of this topic resulted in a cumulative high priority ranking. This ranking was based predominately on the relatively low cost of implementing the project. The NRC rated the importance of the five GTG start logic modifications as low and the light-off speed and generator e>. citation trips as medium.

The general issue of GTG reliability is important to resolution of the station blackout issue. However, NNECO believes the issue of GTG reliability should be addressed in its entirety, rather than on a piecemeal basis. NNECO is currently actively pursuing resoluthn of the station blackout issue through industry groups.

In addition, NNECO has been evaluating the performance of the GTG and has instituted a preventive maintenance program for the GTG. Finally, NNECO has recently completed a reliability model for the GTG, intended to predict potential problem areas within the GTG system. Based on this model, NNECO expects to determine positive changes for existing GTG procedures and programs.

Accordingly, as one aspect of NNECO's efforts to address station blackout and other longer-term GTG reliability issues, NNECO has scheduled the modifications as discussed above in the 115 to be completed by the end of the Cycle 12 refueling outage. Any further modifications will be factored into the 11S as identified.

Topic 1.02 - Tornado Missile Protection ISAP Topic 1.02 addresses the need to provide a missile protected source of make-up water to the Isolation Condenser (IC). The project under consideration proposes a design change to provide a portable engine-driven pump and a tornado missile protected offsite water supply to provide make-up to the IC following a loss of normal power (LNP) event caused by a tornado.

NNECO's initialISAP assessment of this topic resulted in a high priority ranking.

However, NNECO's ISAP assessment assumed no backfeed capability from Millstone Unit No. 2 to Millstone Unit No.1. Implementation of the backfeed (ISAP Topic 1.16.1) significantly reduces the marginal benefit of providing a missile protected source of make-up water to the IC because power through the backfeed will be available to provide make-up to the IC. In addition, modifications of the control rod drive (CRD) pumps (ISAP Topic 1.16.2) are being made to allow for CRD pump operation without an external source of cooling wa ter. The IIS reflects that Topics 1.16.1 and 1.16.2 will be completed by the end of the 1987 refueling outage.

Attachment A

-B12529/Page 2 It is noted that the potential increase in public safety as determined in the initial ISAP evaluation was the .only factor driving implementation of this project.

Personnel safety and economic performance were not affected and NNECO

> estimated a decrease in personnel productivity due to increased maintenance and surveillance. However, due to the potential public safety benefits and the integration of this topic with topics 1.16.1 and 1.16.2, NNECO plans to further study this issue to assure that all tornado missile concerns are adecuately

. addressed. Accordingly, NNECO has scheduled in the IIS, a study of this topic which will be completed by June 1988.

Topic 1.03 - Containment Isolation - Appendix A Modifications Under this topic, NNECO evaluated a specific proposed project to relocate the cooling return line tie-in to the low pressure coolant injection (LPCI) suction line from upstream to downstream of pump suction valves 1-LP-2A and 2B.

NNECO's ISAP. assessment of this topic resulted in a low priority ranking.

' NNECO did not find any benefits to public safety (no impact on core melt frequency), economic performance, personael safety, or personnel productivity from implementation of this project. The NRC in the draf t ISAR also found the priority ranking to be low.

Based on the above, the expected personnel exposure related to the installation of this project (5 man-rem), and an estimated cost of approximately $250,000, NNECO sees no benefit in implementing this project and plans 'to drop this

. project from further consideration.

- Topic 1.04 - RWCU Pressure Interlock ISAP Topic 1.04 addresses a project to install a second independent pressure

' interlock for the in-board suction isolation valve. This interlock is intended to ensure system isolation in the event that the pressure regulating valve fails in

' the wide-open position.

NNECO's ISAP assessment of this topic resulted in a low priority for implementation. The analysis found only a very small increase in public safety (there would be a very small change in small break LOCA frequency and a ;

change in core melt frequency on the order of 10-8/ year). Even this small i benefit was offset by a decrease in personnel safety due to increased occupational exposure. In~ draft NUREG-il84 (the ISAR), the NRC also j concluded that the disadvantages of this project outweighed any benefits and, 1 therefore, that an independent pressure interlock is not warranted.

j As such, NNECO plans to drop this topic from further consideration.

- Topic 1.05 - Ventilation System Modifications ISAP Topic 1.05 addresses the following two issues: I

a. Modification of the electrical supplies for the feedwater/FWCl area coolers so that all six area coolers are automatically sequenced onto q

a gas turbine-powered bus following an LNP. 4

Attachment A B12529/Page 3

b. Modification to the power supply for the intake structure exhaust fans to allow automatic sequencing of one fan onto a gas turbine bus and the other fan onto a diesel generator bus.

NNECO's ISAP assessment of these issues resulted in a high implementation priority for modifications to the electrical supplies for the feedwater/FWCI area coolers and a low implementation priority for the modification of the powet supply for the intake structure exhaust fans.

The high ranking for the feedwater/FWCI area cooler electrical supplies

,, modifications was based on the potential for accelerated aging of the condensate and condensate booster pumps due to a loss of cooling in the area. This could lead to these pumps failing, leading to c total failure of the feedwater/FWCI system.

The low ranking for the modification to the power supply for the intake structure exhaust fans was based on the fact that the intake structure exhaust fans would not affect operation of emergency service water even if thev failed. !

No other attribute benefits were found for either issue evaluated under this topic. Consistent with the ISAP findings and rankings, NNuCO has scheduled the project to provide emergency power to the FWCI space coolers in the IIS to be completed by the end of the 1987 refueling outage. NNECO plans to drop proposed modifications to the intake structure ventilation system, which were determined to be of no benefit.

Topic 1.06 - Seismic Qualification of Safety-Related Piping ISAP Topic 1.06 addresses concerns related to the ability of plant structures and equipment to function following an earthquake. NNECO's ISAP assessment of this topic resulted in a low priority ranking. This ranking was based on a marginal increase in public safety which was offset by a decrease in personnel safety and personnel productivity.

At the present time, there are approximately 300 out of the original 1,100 modifications remaining to be implemented. During the 1987 outage, NNECO will complete up to one-half of the remaining hangers, depending on the availability of craf t personnel and outage duration. Following these current ,

outage activities, NNECO will have spent approximately 51 million dollars and significant man-rem in installation doses on this topic. NNECO will have completed over 900 of the hanger modifications. The remaining modifications offer only marginal additional benefit in public safety and are estimated to cost another 7 million dollars (engineering and construction) and additional installation exposures. Based on the marginal value of the modifications that will remain after the Cycle 11 outage, the high " costs" associated with seismic upgrades as indicated above, and the magnitude of NNECO's efforts already completed on this project, NNECO plans to reevaluate this issue to determine whether the remaining effort is warranted. This reevaluation is expected to be completed by March,1988.

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' Attachment A j B12529/Page 4 1 Topic No.1.07 - Control Room Design Review ISAP Topic 1.07 addresses the Control Room Design Review (CRDR) for Millstone Unit No.1. NNECO's ISAP assessment of this study resulted in a medium implementation priority for the study.

As noted in the ISAR, NNECO submitted a program plan and schedule for the CRDR 'on March 2,1987.(l) This submittal is currently under Staff review.

NNECO has scheduled the CRDR study in the IIS in accordance with the schedule proposed in NNECO's earlier submittal. (NNECO has proposed to submit the CRDR Summary Report by February 28, 1989.) Any proposed modifications that result from the CRDR will be evaluated in the ISAP and will be factored into the l IIS at a later date.

Topic No.1.08 - Safety Parameter Display System ISAP Topic ~1.08 addresses the installation of a Safety Parameter Display System (SPDS) at Millstone Unit No.1. In its ISAP evaluation, NNECO ranked this '

project as a medium priority. In the ISAR, the NRC Staff concluded that, given the . fact that the plant process computer and associated equipment is already being upgraded (ISAP Topic 2.03), the priority for this project should be higher.

Although NNECO does not believe its project ranking to be inappropriate, for implementation purposes SPDS is a logical follow-on project to the process computer replacement. NNECO has scheduled this topic in the 115 to be completed within six months following start of Cycle 12 or by February 15, 1988, whichever is later.

Topic No.1.09 - Regulatory Guide 1.97 - Instrumentation ISAP Topic 1.09 addresses nine potential instrumentation modifications to bring Millstone Unit No.1 into conformance with Regulatory Guide 1.97. The nine areas addressed were:

a. RPV Pressure

b. RPV Water Level

c. Neutron Flux

d. Drywell Temperature

e. Drywell Spray Flow

f. IC Shell-Side Water I.evel

g. IC System Valve Position

h. Ventilation Damper Position

i. Primary Containment Isolation Valve Position NNECO's analyues showed that only the proposed modification to the drywell temperature indication would provide any significant benefit. NNECO has scheduled this project (which is the same as the resolution of Topic 2.02/2.25) in the 115 to be completed by the end of the 1987 refueling outage. The drywell temperature indication modification will cost NNECO almost twe million dollars and significant estimated (22 man-rem) exposure.

Instrumentation related to reactor pressure vessel water level was evaluated under ISAP Topic 1.13 and is addressed further under that topic. Similarly, ventilation damper position was addressed under ISAP Topic 1.12.

Attachment A j B12529/Page 5 The remaining issues under this topic were found in the integrated assessment to

, have little or no significance from a safety or operational standpoint. Moreover, l NNECO considers the value of these instruments to be further diminished by the fact that Millstone Unit No. I has symptom-oriented emergency operating procedures (EOPs). Symptom-oriented EOPs are not system-oriented. Hence, these provide guidance to operators based on global core and containment conditions.

Specifically, RPV pressure was found to provide no reduction in core melt frequency or public risk. The range instrumentation which is proposed would not affect operator actions during an accident scenario. Loss of indication would not inhibit any transient mitigation efforts. '

Additional environmentally qualified neutron flux indication also would not reduce public risk. Based on existing operating procedures, loss of neutron flux monitoring would not prevent the operator from bringing the plant to safe shutdown.

Redundant and environmentally qualified drywell spray flow instrumentation also is unwarranted at this time. Use of drywell sprays is not credited in the current design basis analyses. Furthermore, under the existing EOPs, very restrictive conditions exist for which the drywell sprays could be utilized post-accident. As such, improved drywell spray flow indication would not result in an increase in public safety. NNECO believes no immediate modifications in this area are warranted and this issue should be evaluated in conjunction with the resolution of severe accident issues.

IC condenser shell-side water level, primary containment isolation valve position, and IC system valve position instrumentation modifications were all found to provide insignificant reductions to the core melt frequency at the plant.

Loss of the instrumentation would not h!nder the operator's ability to mitigate the consequences of an accident.

The overall . costs of implementing hardware modifications toadowss these concerns would be high both in terms of capital-budget dollars and occupational I exposures. It is estimated that the costs would run into the hundreds of thousands of dollars with an average exposure on the order of several man-rem per modification. This estimate is supported by the costs discussed above related to installation of the drywell temperature indication.

In summary, drywell temperature indication, despite significant costs, will be completed during the Cycle 11 refueling outage because it allows EOP execution based upon environmentally qualified indication and offers positive benefits with respect to the containment purge and vent issue. Based on the low benefit of the other proposed modifications, and the potentially high installation costs and man-rem exposure, NNECO plans to drop those projects from further consideration.

Topic 1.10 - Emergency Response Facilities Instrumentation ISAP Topic 1.10 addresses the criteria of Generic Letter 32-33 related to Emergency Response Facilities information. This topic was ranked as a low priority by the NRC. NNECO's ISAP assessment of this topic resulted in a

l- Attachment A I B12529/Page 6 medium implementation priority. This.was based on the conclusion that some additional means of providing real time data to personnel in the Technical Support Center, Emergency Operating Facility and the Corporate Emergency Operations Center would be beneficial. As this project can be implemented while the plant-is on line, NNECO has scheduled this topic in the 115 to be completed by the end of the second quarter of 1988.

Topic 1.11 - Post-Accident Hydrogen Monitor In response to the post-accident monitor criteria of the TMI Action Plan, NNECO installed a single channel hydrogen monitoring system at Millstone Unit No. 1. In addition, the existing post-accident sampling system (PASS) can provide information on containment atmosphere hydrogen concentration. ISAP Topic 1.11 addresses the need for a redundant hydrogen monitor at Millstone-Unit No.1.

NNECO's ISAP evaluation of this topic resulted in a low priority ranking. The frequency 'of a LOCA occurring during the time the containment is deinerted accompanied by a failure of the two existing hydrogen monitoring methods is extremely small. In a letter. dated July 31, 1986, NNECO provided additional information supporting its conclusion that the hydrogen monitoring system-presently installed at Millstone Unit No.1, in conjunction with the existing PASS, is acceptable and that addition of a redundant hydrogen monitoring system 'would have a negligible impact on public safety. As noted in the ISAR, this information is still under review by the Staff. No activities are currently scheduled in the 115.

(Note: Additional technical information on this topic is provided in Attachment B.)

Topic 1.12 - Control Room Habitability ISAP Topic 1.12 addresses the protection of control room operators against the effects of an accidental release of toxic or radioactive gases such that the plant can be safely shut down under design basis accident conditions.

NNECO's ISAP assessment of this topic resulted in a low implementation priority. The result was based on the fact that the safety benefit of the project was greatly reduced by the implementation of ISAP Topic 2.07, which removed the remaining chlorine tank cars from the Millstone siu. In addition, the analyses showed any further reduction in core melt frequenc< at Millstone Unit No. I from implementation of this project to be minimal.

Furthermore, from a personnel safety and personnel productivity standpoint, this project had a large negative impact. Occupational exposure is expected to increase due to increased surveillance and maintenance activities related to the installation of coolers, dampers, charcoal filters, etc. This would also affect productivity as the additional equipment would require surveillance and maintenance activities beyond that which is required for the current system.

Another factor NNECO has considered is the costs involved in implementing this project. Although equipment for this project has been purchased, the remaining costs for engineering and installation of the system are over 5 million dollars. In

Attachment A B12529/Page 7-addition, as this project requires major modifications in the control room, it is expected to add significantly to the length of future outages.

As such, the costs of implementing this project far outweigh any benefits that could be achieved. NNECO plans to drop this project from further consideration.

Topic 1.13 - BWR Vessel Water Level Instrumentation ISAP Topic 1.13 addresses proposed modifications to assure accurate indication of vessel water level. Specifically, in the integrated assessment, NNECO evaluated the impact of a study to address a concern that the operator be able to recognize reference leg flashing. NNECO's ISAP assessment of this topic resulted in a high ranking among the studies considered in the ISAP.

Subsequent to the ISAP evaluation, NNECO has further studied this issue in light of the resolutions of other ISAP topics. NNECO has concluded that, in conjunction with the existing feedwater system, NNECO's commitment to install the SPDS (Topic 1.08) satisfactorily addresses this issue. The SPDS will include indication that would alert operators to reference leg flashing. This will significantly lower the probability that operators would misinterpret vessel water level readings by not realizing that the reference legs wmc flashing. The drywell temperature upgrade (ISAP Topic 2.25) will also imprwe the operator's knowledge of reference leg flashing.

Moreover, reference leg flashing occurs when the drywell heats up to the saturation temperature of the water in the reactor vessel. In the event of a small break LOCA, which was found to be the dominant LOCA contributor to core melt relative to operator error in water level interpretation, successful feedwater operation will keep the RPV from reaching saturated conditions. In the original ISAP evaluation, the Millstone Unit No. I feedwater system was not credited in preventing flashing.

As such, if both SPDS and the feedwater system are considered in a new ISAP evaluation, potential further modifications to address this issue would receive an ISAP public safety score of less than 0.1. Based on these assessments, NNECO plans to drop Topic 1.13 from further consideration and considers this issue to be resolved. This topic again illustrates the benefits of an integrated review of related topics.

Topic 1.14 - Appendix 3 Modifications This topic encompasses NNECO's effort to identify any remaining areas of noncompliance with 10CFR50, Appendix 3 and the proposed modifications to resolve such open issues. In the ISAP evaluation, NNECO concluded that the specific proposed projects were a low priority.

On November 19, 1986,(2) NNECO supplemented the ISAP final report on this topic, presented the status of the issue, and identified the exemptions from 10CFR50, Appendix 3 that it would seek. Based on further evaluation, NNECO now intends to evaluate cartain, selected penetrations using the ISAP Public l Safety Impact Assessment methodology. The purpose of the evaluation is to I

determine if modifications to permit Appendix 3 testing are warranted for those selected penetrations. NNECO is currently preparing exemption requests for the

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. Attachment A B12529/Page 8 remaining penetrations identifie.d in the November,1986 Jetter. Accordingly, NNECO has scheduled in the IIS, final resolution of this issue by December 15, 1987.

Topic 1.15 - FSAR Update ISAP Topic 1.15 addresses NNECO's efforts to update the Millstone Unit No.1 Final Safety Analysis Report (FSAR). In the ISAR, the NRC Staff noted that, by letters dated December 17, 1986 and March 27, 1987, NNECO submitted the updated Millstone Unit No.1 FSAR. NNECO concurs with the Staff's conclusion that this topic is resolved.

Topic 1.16 - 10CFR50, Appendix R This topic includes 12 items to address 10CFR50, Appendix R (ISAP Topics 1.16.1

- 1.16.12). All except several aspects of Topic 1.16.6 have either been completed or are scheduled in the IIS to be completed by the end of the 1987 refueling outage. This scheduling has been based more upon external impacts than upon the ISAP ranking. NNECO has addressed these matters essentially at the request of the NRC staff.

Remaining aspects of Topic 1.16.6 involve installation of a water curtain, protecting the turbi:.e building floor supports, and protecting the structural steel in the mezzanine area. NNECO has addressed this topic as a routine licensing matter, concluding that J necessary to comply with Appendix R.\gese proposed In total, modifications NNECO believes thisare nothas been topic adequately addressed. IndividuC topics should be closed as the scheduled modifications are implemented.

Topic 1.17 - Replacement of Motor-Operated Valves ISAP Topic 1.17 addresses the qualification and/or exemption of 11 motor-operated valves (MOVs) that have not yet been qualified to achieve total compliance with 10CFR50.49. NNECO's ISAP assessment of this topic resulted in a probabilistic evaluation of medium priority ranking. Moreover, as noted by the Staff in the ISAR, NNECO requested an exemption for the 11 valves by letter dated January 17, 1986. NNECO subsequently withdrew the request for exemption for two valves (Valves 1-RR-2A and B) by letter dated March 12, 1987. NNECO will qualify these two valves by the end of the 1987 refueling outage. Also, following discussions with the NRC Staff in which the Staff indicated that an exemption would not be granted for Valve 1-IC-2, NNECO i subsequently agreed to qualify Valve I-IC-2 during the 1987 outage. '

The Staff issued its safety evaluation report on the remaining eight exemption requests on June 8,1987. The Staff, in the SER, granted the requested exemptions for seven of the valves and concluded that the eighth is outside the scope of equipment required to be environmentally qualified. NNECO concludes that it is now unnecessary to schedule any further modifications to resolve this topic in the IIS. Following the 1987 outage and qualification of the three valves identified above, this topic should be closed.

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Attachment A B12529/Page 9' Topic 1.18 - ATWS This ISAP Topic addresses Millstone Unit No. I's compliance to the requirements

. of 10CFR50.62 related to the Standby Liquid Control System (SLCS). As noted in the ISAR, NNECO has committed to resolve this issue by using enriched boron (BIO)in the SLCS to achieve control capacity equivalent to 86 gpm of 13 weight percent sodium pentaborate solution. NNECO previously committed to perform this modification at the earliest outage consistent with delivery of the enriched boron. This topic has now been scheduled in the 115 to be completed by the end of the 1987 refueling outage.

Topic 1.19 -Integrated Structural Analysis This ISAP topic addresses several remaining SEP concerns related to the structural integrity of Millstone Unit N 1. The topic was' not evaluated by NNECO and has been handled as a routine ucensing issue.

As noted by the Staff in the ISAR, there is only one remaining open item under this topic. NNECO has submitted information necessary to resolve this issue, which concerns the. adequacy of NNECO's assumptions on plant materials.and backfill amounts. No activities are currently scheduled in the IIS, pending Staff review of the recently submitted information.

Topic 1.20 - MOV Interlocks ISAP Topic l.20 concerns thermal overload protection for motors of motor-operated valves. As noted by the Staff in the ISAR, this issue is resolved.

' Topic 1.21 - Fault Transfers This ISAP topic addresses the design of seven automatic bus transfer (ABT)

- devices and the possible need for interlocks on three load centers that are manually transferred between redundant sources.

NNECO's ISAP assessment of this topic concluded that proposed modification of six ABT devices would result in either no significant impact on pub!!c risk or an actual slight increase in public risk. NNECO therefore concluded that this project should be closed. (The seventh ABT has been disarmed and thus was not evaluated. Also, as stated in the ISAP final report, the need for interlocks on the three load centers is no longer an issue.)

In the ISAR, the Staff refined the scope of the topic. The Staff concluded that if the ABTs 'at issue are removed from the LPCI system, the reliability of the l system will be reduced. However, the Staff concluded that this will not result in a significant increase in core melt frequency. Moreover, the Staff suggested that if the LPCI system is modified to provide redundancy when the system is in the alternate shutdown cooling mode, the topic could have a greater impact on public risk. The. Staff rated implementation of this project as a medium priority.

Preliminary reassessments of the LPCI system show that a fully redundant system would not produce a significant reduction in core melt frequency. In addition, the likelihood of fault transfers between buses is extremely low due to the various levels of electrical protection (e.g., circuit breakers). Consequently, NNECO believes this project should be closed.

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Based on the above, and upon its ISAP assessment of this topic, which resulted in a low pr.wity ranking (number 10 of 10 among studies), NNECO does not plan L any further consideration of this topic. If the Staff requests additional analyses on a' refined scope related to. this topic, NNECO believes the Staff should present this additional request for topic review in the form of a new ISAP topic.

Topic 1.22 - Electrical Isolation This ISAP topic encompasses a review of electrical isolation provisions at Millstone' Unit No. I against the criteria of 10CFR50.55a(h) and IEEE Std. 279-1971. These criteria ensure that safety signals are isolated from nonsafety signals and that no credible failure at the output of an isolation device can prevent the associated protection system channel from meeting the minimum performance requirements. This topic at present involves a study rather than specific plant modifications.

As noted in the ISAR, NNECO has provided the Staff with information to resolve this issue. The information is currently under Staff review. Any additional information required by the Staff will be submitted at a later date. At such time as a specific further study or specific plant modification is identified, NNECO will schedule the topic in the 115.

Topic 1.23 - Grid Separation Procedures Topic 1.25 - Degraded Grid Voltage Procedures These two ISAP topics encompasses a review and evaluation of the plant power supply system against the criteria of GDC-17 with regard to the ability of the plant to cope with a degraded grid voltage condition. The specific safety concern is the potential for equipment damage to occur if the grid voltage were to degrade and become low enough so that the voltage at the Class IE equipment is less than the qualified operating voltage.

As noted in the ISAR, NNECO previously committed to complete final degraded grid voltage modifications to resolve this issue r.'uring the 1987 refueling outage.

NNECO's commitment to complete these modifications during the 1987 outage (deferred from the 1985 outa6e) was based on a PSS evaluation that concluded that the planned modifications would increase the probability of a station blackout and that, prior to the 1987 outage. t% modifications could be further refined.

NNECO presently has dropped implementation of the redesign of the degraded grid voltage protection system from the 1987 refueling outage schedule. Based on its latest evaluations of this issue utilizing the Millstone Unit No. I plant-specific simulator, NNECO has concluded at this time that the disadvantages of various proposed modifications offset any possible benefits.(4)

In a letter dated June 9, 1987, the NRC concurred on the delay of implementation of this project and stated that modifications to address this issue should be implemented during the 1989 refueling outage. NNECO is currently evaluating potential modifications to address this issue and has scheduled any necessary modifications in the IIS to be completed by the end of the 1989 (Cycle 12) refueling outage.

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Attachment A l B12529/Page 11 Topic No.1.24 - Emergency Power ISAP Topic 1.24 encompasses a review of the Millstone Unit No. I gas turbine generator (GTG) maintenance program.

As stated in the ISAP final report, NNECO believes that this issue is resolved.

NNECO has provided the NRC Staff with a summary of NNECO's thorough review of the preventive maintenance program for the GTG, and the improvements and corrective actions that have been identified and implemented.

The Staff, in its March 3,1986 review of the scope of ISAP topics, also concluded that this topic is closed. (See also Table 2.2 of the ISAR.)

Nevertheless, in the ISAR, the Staff concluded that "to better address the issue of station blackout at Millstone Unit No.1, the Staff has expanded the scope of this topic." The Staff recommended four specific actions to further bolster its program for maintaining and monitoring the GTG. The Staff rated these recommendations as a medium priority for implementation.

NNECO has not yet evaluated these recommendations or scheduled them for implementation. NNECO continues to believe that this ISAP topic is resolved.

Any further measures addressing GTG reliability, such as those suggested by the Staff in the ISAR, should be addressed in the context of the broader station 1 blackout and GTG performance issues. See the write-up on ISAP Topic 1.01 for further details of NNECO's efforts related to the gas turbine generator.

Topic 1.26 - Equipment Classification / Vendor Interface (GL 83-28, item 2.1)

As noted in the ISAR, the Staff has issued an SER resolving part of this topic and requesting additional information to resolve the remaining portion. NNECO submitted this additional information to the NRC and is addressing this topic as a routine licensing matter. Pending NRC review, no IIS implementation schedule is necessary.

Topic 1.27 - Port-Maintenance Testing (GL 83-28, items 3.1.1 and 3.1.2)