ML20246M138

Comments on Util Response to Generic Ltr 88-17 Re Expeditious Actions for Loss of Dhr.Response Generally Acceptable But Lacked Details for Listed Subjs

ML20246M138
Person / Time
Site:	Millstone
Issue date:	05/08/1989
From:	Vissing G Office of Nuclear Reactor Regulation
To:	Mroczka E CONNECTICUT YANKEE ATOMIC POWER CO., NORTHEAST NUCLEAR ENERGY CO.
References
GL-88-17, TAC-69754, NUDOCS 8905190054
Download: ML20246M138 (6)

Text

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4 UNITED STATES NUCLEAR REGULATORY COMMISSION -

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May 8, 1989 Docket No. 50-336 Mr. E. J. Mroczka

' Senior Vice President Northeast Nuclear Energy Company Connecticut Yankee Atomic Power Company P. O. Box 270-Hartford, Connecticut 06141-0270

SUBJECT:

COMMENTS ON THE NORTHEAST NUCLEAR ENERGY COMPANY RESPONSE TO GENERIC LETTER 88-17 WITH RESPECT TO EXPEDITIOUS ACTIONS t

FOR LOSS OF DECAY HEAT LEMOVAL FOR MILLSTONE NUCLEAR POWER l

STATION, UNIT 2 (TAC NO. 69754)

GenericLetter(GL)88-17wasissuedonOctober 17, 1988 to address the potential for loss of decay heat removal (0HR) during.nonpower operation.

In the GL, we cequested (1) a description of your efforts to implement the eight recommended 3

expeditiousactionsoftheGL,and(2)adescriptionofthe' enhancements, specific plans and a schedule for implementation of the six recommended program 3

enhancements.

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The NRC staff has reviewe'd your response to Generic Letter 88-17 on expeditious actlons dated December 23, 1983. We find that it appears to meet the staff's i

intent but lacks some of the details represented in Enclosure 2 of GL 88-17.

Your responses were, for the most part, complete but brief for some items and therefore did not allow us to fully understand your actions takeniin response.

to GL 88-17. You may wish to consider several observations in order to assure yourselves that the actions are adequately addressed:

1.

You have provided an extensive list of training reldted to reduced RCS inventory operatien, where lowered loop operations are anticipated, with licensed and unlicensed personnel of your staff.

In the GL this item was intended to include all personnel who can affect reduced inventory opera-tion, including maintenance personnel. Although you state that maintenance personnel do not receive NSSS classroom system training, you have indicated that avoidance of maintenance-related NSSS perturbation is achieved by supervisory control of maintenance activities. You have further stated that during plant outages, daily meetings are conducted among the various maintenance and operations activities. At these meetings the supervisor

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1 should inform the maintenance personnel of their possible harmful inter-action with mid-loop operation. Precautions for avoidance should be explained, including a background of past problems experienced at other l

plants and.for Millstone Unit 2, if any, i

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Mr. E. J. Nroczka 2.

You indicate that analyses are currently ongoing to clarify NSSS transient response information and that procedures and administrative controls will be revised to address containment closure requirements. Your current estimated time for containment closure of 122 minutes was calculated with input that included a decay heat rate conservatively predicted assuming a decay time of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. As noted in GL 88-17, shorter closure times may l

be necessary if there are openings in the cold 'eg totaling greater _ than 1 square inch (see Enclosure 2, Section 2.2.2 of GL 88-17). Your analyses should be careful to include consideration of such potential openings.

3.

In some plants, the quick closure of the equipment hatch is achieved by the installation of a reduced number of bolts.

If you plan to use less than the full complement of bolts for sealing the equipment hatch, then you should first verify that you can make a proper seal of the periphery mating surfaces to meet the closure criteria.

4.

In your addressing of containment closure, no information is provided regarding how you will keep track of and control the many potential openings which may have to be closed simultaneously. We assume your procedures and administrative controls will address this topic.

5.

You have identified penetrations of concern as those "providing a direct path from the containment atmosphere to the outside atmosphere...."

However, we are concerned with all containment penetrations that could cause a release (e.g., penetrations from the containment into a fuel handling or auxiliary building).

6.

In regards to temperature measurement, you have indicated that four of the eight heated and unheated pairs of thermocouple from each of the two channels (probe A and probe B) of the reactor vessel level monitoring systems (RVLMS) are in contact with the RCS inventory when drained to mid-loop conditions. Accordirig to Figure 2, these are located at four discrete locations in the core. These include heights equivalent to the centerline of the hot and cold legs to a location approximately 40 inches below. You plan to use at least one unheated thermocouple in each channel of the RVLMS to provide a representative core exit temperature. You indicate that the RVLMS readings are continuously displayed in the control room. However, you did not indicate if they also have continuous alarm capability or periodic recording if no continuous alarm. Also, the accuracy of the RVLMS thermocouple was not mentioned.

It is not clear from your presentation if crosschecks aaainst RVLMS thermocouple would be feasiblewiththeshutdowncooling(SDC)systemandcoreexitthermocouples.

7.

You have indicated that two independent, continuous RCS water level indications are to be used for the reduced inventory condition. These are a RVLMS and a temporary tygon tube system. The RVLMS level measure-ment uses a single channel of the RVLMS and provides a continuous display of reactor vessel level at eight discrete points above the core.

o Mr. E. J. Mroczka.,.

As shown on your Figure 2, three of the discrete points correspond to the top, centerifr,e and bottom of the hot leg. The lowest height that can be measured is approximately 40 inches below hot leg centerline. The accuracy of the RVLMS is not provided.

Its usefulness for mid-loop operation is limited because of the wide spread of the discrete level points. The most useful point for mid-loop operation is the one at the hot leg centerline level which would be helpful for comparison against the tygon tube reading.

You have not indicated if this system has alarm capability or if readings ard periodically recorded if no alarm.

You indicate that the tygon tube level detection system will be monitored by closed circuit TV to provide continuous level indication in the control room. This system does not appear to be capable for alams and you have not indicated the frequency of recording the readings in the control room.-

As shown in your Figure 1, the taps are located at the bottom of the hot leg and at a point in the piping interconnecting the top of reactor vessel head and the top of the pressurizer. From the diagram in your Figure 1, it cannot be determined if there are any problems related to the slopes of the vent piping. The pressure in the reference leg should approximate the pressure of the void in the hot leg or be compensated to obtain the correct value. Fron the gauge shown in Figure 1 and the span for the tygen tube reading shown in your Figure 2, it can be seen that the lower range of level reading extends only the limited amount of 15 inches below the centerline of the hot leg.

Because the tap is shown to be at the bottom of the hot leg on Figure 1, it appears that the tygon tubing lower range could be extended further, if helpful. You have not indicated what the accuracy of the system is. When two instruments are in place, another precaution is to resolve any discrepancy in level between the two measure-ment systems.

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8.

Walking the tygon tube following installation to verify lack of kinks or loop seals is necessary. Experience shows that periodic walkdowns are needed after installation. We recorrnend daily walkdowns when the tygon tube is in use, with an additional walkdown immediately prior to its being placed in use.

9.

You have indicated that your backup means for adding inventory to the RCS include using a HPSI pump and charging pumps. You state that these can be aligned for hot leg injection via auxiliary spray in the pressurizer surge line. Also, you are performing analyses to quantify the amount of makeup rate.

If you plan to use a vent in the pressurizer for the opera-tion, your calculation should include an analysis to check on the effect of countercurrent steam flow from the reactor through the hot leg into the pressurizer surge line. This steam flow could be sufficiently great to prevent any injected makeup water from downflowing from the pressurizer spray.

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Mr. Edward J. Mroczka '

Millstone Nuclear Power Station f

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0 Northeast Nuclear Energy Company Unit No~. 2

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cc:

Gerald Garfield, Esquire.

R. M. Kacich, Manager

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' Day, Berry and Howard Generation-Facilities Licensing

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-Counselors at Law Northeast Utilities Service Company City Place Post Office Box 270 Hartford, Connecticut 06103-3499 Hartford, Connecticut 06141-0270 W. D. Rosberg, Vice President D. 0. Nordquist Nuclear Operations Manager of Quality Assurance-Northeast Utilities Service Company-Northeast Nuclear. Energy Company Post Office Box 270

' Post Office Box 270 Hartford, Connecticut 06141-0270 Hartford, Connecticut 06141-0270 Kevin McCarthy, Director Regional Administrator Radiation Control Unit Region !-

Department of Environmental Protection U. S. Nuclear Regulatory Commission State Office Building 475 Allendale Road Hartford, Connecticut 06106 King of Prussia, Pennsylvania 19406 Bradford S. Chase, Under Secretary First Selectmen Energy ~ Division.

Town of Waterford.

Office of Policy _ and itanagenent Hall of Records 80 Washington Street.

200 Boston Post Road Hartford, Connecticut 06106 Waterford, Connecticut 06385 S. E. Scace, Station Superintendent W. J. Raymond, Resident Inspector' Millstone Nuclear Power Station Millstone' Nuclear Power Station Northeast Nuclear Energy Company c/o U. S. Nuclear Regulatory Commission Post Office Box 128 Post Office Box 811 Waterford, Connecticut 06385 Niantic, Connecticut 06357

'J. S. Keenan, Unit Superintendent Charles Brinkman, Manager Hillstone Unit No.~2 Washington Nuclear Operations Northeast Nuclear Energy Company C-E Power Systeir.s Post Office Box 128 Combustion Engineering, Inc.

Waterford. Connecticut 06385 12300 Twinbrook Pkwy Suite 330 Rockville, Maryland 20852 l

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l Mr. E. J. Mroczka l

10. You have not stated the use of any specific vent opening on the hot side of the P,CS to relieve RCS pressurization. The removal of a pressurizer manway or steam generator manway, for example, are means to provide RCS venting. Calculations need to be performed to verify the effectiveness of RCS openings, however, because even for relatively large hot side openings in the RCS, pressurization to several psi can still result.

For example, with removal of a pressurizer manway large steam flows in combination with flow restrictions in the surge line and lower pressurizer hardware may still lead to pressurization.

There is no need to respond to the above observations.

As you are aware, the expeditious actions you have briefly described are an interim measure to achieve an immediate reduction in risk associated with reduced inventory operation, and these will be supplemented and in some cases replaced by programmed enhancements. Ve intend to audit both your response to the expeditious actions and your programmed enhancement program. The areas where we do not fully understand your responses as indicated above may be covered in the audit of expeditious actions.

This closes out the staff review of your responses to the expeditious actions listed in the GL. The area of programmed enhancements will be addressed in a separate letter.

Sincerely, original signed by Guy S. Vissing, Project Manager Project Directorate I-4 1

Division of Reactor Projects I/II Office of Nuclear Reactor Regulation

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g Mr. E. J. Mroczka 10. You have not stated the use of any specific vent opening on the hot side of the RCS to relieve RCS pressurization. The removal of a pressurizer manway or steam generator man <ay, for example, are means to provide RC4 venting. Calculations need to be performed to verify the effectiveness of RCS openings, however, because even for relatively large hot side openings in the RCS, pressurization to several psi can still result.

For example, with removal of a pressurizer manway large cteam flows in combination with flow restrictions in the surge li:ie and lower pressurizer hardware may still lead to pressurization.'

There is no need to respnnd to the above observations.

As you.are aware, the expeditious actions you have briefly described are an interim measure to achieve an immediate reduction in risk associated with reduced inventory operation, and these will be supplemented and in some cases replaced by programmed enhancements. Ve intend to audit both your response to the expeditious actions and your programmed enhancement program. The areas where we do not fully understand your responses as indicated above may be covered in the audit of expeditious actions.

This closes out the staff review of your responses to the expeditious actions listed in the GL. The area of programmed enhancements will be addressed in a separate letter.

Sincerely, original signed by Guy S. Vissing, Project Manager Project Directorate I-4 Division of Recctor Projects I/II Office of Nuclear Reactor Regulation cc: See next page DISTRIBUTION Docket' W NRC & Local PDRs Plant File SVarga BBoger SNorris GVissing OGC EJordan BGrimes ACRS(10)

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