ML20244D789

Comments on Util 890106 Response to Generic Ltr 88-17 Re Expeditious Actions for Loss of DHR for Plant.Expeditious Actions Re Reduction in Risk Associated W/Reduced Inventory Operation Will Be Replaced by Programmed Enhancements

ML20244D789
Person / Time
Site:	Prairie Island
Issue date:	06/12/1989
From:	Diianni D Office of Nuclear Reactor Regulation
To:	Parker T NORTHERN STATES POWER CO.
References
GL-88-17, TAC-69767, TAC-69768, NUDOCS 8906190259
Download: ML20244D789 (5)

Text

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• June 12, 1989 Docket Nos. 50-282 and 50-306 Mr. Tom Parker Manager Nuclear Support Services Northern States Power Company 414 Nicollet Mall Minneapolis, Minnesota 55401-1927

SUBJECT:

COMMENTS ON THE NORTHERN STATES POWER COMPANY RESPONSE TO GENERIC LETTER 88-17 WITH RESPECT TO EXPEDITIOUS ACTIONS FOR LOSS OF DECAY HEAT REMOVAL FOR PRAIRIE ISLAND NUCLEAR GENERATING PLANT UNITS 1 AND 2 (TAC NOS. 69767 AND 69768)

Generic Letter (GL) 88-17 was issued on October 17,.1988 to address the potential loss of decay heat removal (DHR) during nonpower operation. In the GL, we requested (1) a description of your efforts to implement the eight recommended expeditious actions of the GL and (2) a description of the enhancements, specific plans and a schedule for implementation of the six recommended program enhancements.

The NRC staff has reviewed your response to Generic Letter 88-17 on expeditious actions in the letter of January 6,1989. Your letter also had responses for programmed enhancements. However, these will be reviewed at a later time. We find that your response appears to meet the intent of the GL for expeditious actions but lacks some of the details requested in Enclosure 2 of GL 88-17.

Your response to some items is brief and ".erefore does' not allow us to fully ,

understand your actions taken in response to GL 88-17. You may wish to consider '

several obse'rvations in order to assure yourselves that the actions are adequately addressed. .

1. You mention a training packaged developed for operating crews and appro-priate personnel relating to the Diablo Canyon event, specifics of the RHR system, reactor coolant instrumentation and the Westinghouse Owner's Group (WOG) study. It is not specifically stated if maintenance personnel are

• also included in the training. The item was intended to include all >

personnel who can affect reduced inventory operation.

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2. You indicate that procedures and administrative controls are in place to <

reasonably assure that containment closure can be achieved within the l time at which core uncovery could result from a loss of DHR coupled with an inability to initiate alternate cooling or addition of water to the  !

RCS inventory. You indicate that refinements and modifications are being  !

made to reflect time periods for closure consistent with the GL and WOG '

study. You have not presented the new times for containment closure based on your plant specific analysis. In the meantime, Generic Letter 88-17 states that " containment penetrations including the equipment hatch, may remain open provided closure is reasonably issued within 2.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> of initial loss of DHR." This time will be less if there are vent areas totaling greater than one square inch in the cold leg (see Enclosure 2, Section 2.2.2 of GL 88-17). {

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3. In some plants the quick closing 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 r..eet the closure criteria.

4. You indicate that two core exit thermocouple will be provided for obtaining continuous temperature indication that is representative of core exit conditions when the RCS is in a mid-loop condition. You have stated that the core exit thermocouple use a common power supply. You indicate that a failure of the power supply will cause temperature indications to increase which is in the conservative direction for operator action.

Although, we do not necessarily agree with your statement " Inaccurate temperature indications cannot cause inappropriate operator actions as would inaccurate RCS level indications," nevertheless, we are not calling for independent power supplies, but two different sensors.

5. You indicate that two continuous RCS water level indications are provided to the control room whenever the RCS is in a reduced inventory condition.

In one system, a level transmitter sends signals to a control board level indicator and via a temporary installation, high and low RCS water level alarms are available. Trending of the RCS water level can be performed on the emergency response computer system which also receives the level signal. You have stated that the second RCS water level indication uses a tygon tube which is permanently installed with remote viewing in the control room. You indicate that the level reading is recorded hourly.

You state that if the remote viewing equipment is not operable a designated

" tube watch" operator in contact with the control room will be provided.

As noted in GL 88-17, these observations from other than in the control room should be recorded at intervals no greater than 15 minutes. You have indicated that the common sensing taps for both of the level systems are located off the RCS loop A crossover lege. Since the same commons taps are used for two level systems a common error may occur and extra precautions are needed. You have not stated what the accuracy is of each of the two systems. When two instruments are in place, care should be taken to resolve any discrepancy between the two measurement systems. Also,'the pressure in the reference leg should approximate the pressure of the void in the hot leg or be compensated to obtain the correct level value.

6. 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 recommend daily walkdowns when the tygon tube is in use, with an additional walkdown immediately prior to its being placed in use.

7. For expeditious action regarding provision of at least two available or operable means of adding inventory to the RCS that are in addition to pumps that are a part of the normal DfiR systems, you state that present procedures require the charging system to be operable and give guidance

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on injection rates. You have.not' stated the ' injection point for this system. You further. state that additions to. the procedures will be made g requiring that a safety. injection pump be made available which is' aligned-for upper plenum injection. 'As alluded to in Enclosure 2,.Section 2.'2.2-j q

of GL 88-17, if openings totaling greater than 1 square. inch exists in~ . i the cold legs, reactor coolant pumps.and' crossover. piping of-the RCS, the I core can uncover quickly when pressurized under loss of RHR conditions. l If this situation should arise, it=is generally more effective toc inject' D makeup water.into the hot leg. rather than the cold leg. j 8.

~

You have not, stated the use of any specific vent _ openings on the~ hot-side:

of the RCS to relieve RCS~ pressurization. The removal of a. pressurizer manway or steam generator manway, for example, is a means to provideLRCS.

venting. Calculat. ions ~need to' be performed to . verify the effectiveness of RCS openings, however, because even for'relatively~1arge hot side l 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 iead to pressurization.

There.is'no need to respond to the above observations.-

As you are awar,e,'the expeditious' actions you'have briefly described are an interim measure to achieve an immediate' reduction in risk associated withz reduced inventory operation, and these will be supplemented ~and in some cases replaced by programmed enhancements.. ' We' 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 completes 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,

~ .

W .

, x %: ,

l Dominic C. Dilanni, Project Manager Project. Directorate III Division of Reactor Projects:- III,~IV, V

&'Special, Projects Office of Nuclear. Reactor Regulation 1

_ - _ _ _ _ _ _ - - - _ - _ - _ _ _ _ - _ _ _ - _ - - - _ --_E-__._ -_ ____

Hr. T. M. Parker Prairie Island Nuclear Generating i

Northern States Power Company Plant cc:

Gerald Charnoff, Esq.

Shaw, Pittman, Potts and Trowbridge 2300 N Street, N.W.

Washington, DC 20037 Dr. J. W. Ferman Minnesota Pollutice. Control Agency 520 Lafayette Road St. Paul, MN 55155

' Mr. E. L. Watzl, Plant Manager Prairie Island Nuclear Generating Plant Northern States Power Company Route 2 Welch, Minnesota 55089 Joseph G. Maternowski Assistant Attorney General Environmental Protection Division Suite 200 520 Lafayette Road St. Paul, Minnesota 55155 U.S. Nuclear Regulatory Comission Resident Inspector's Office 1719 Wakonade Drive East Welch,iiinnesota 55089 l

I Regional Administrator, Region III U.S. Nuclear Regulatory Comission Office of Executive Director fu e Operations 799 Roosevelt Road Glen Ellyn, Illinois 60137 l Mr. William Miller, Auditor Lodhue County Courthouse Red Wing, Minnesota 55066 .

I l

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d-1 on injection rates. .You'have not stated the injection point:for this system. ,You further state that additions:to the procedures will be made requiring that a safety' injection pump be made available.which'is aligned for upper plenum injection. ;Ascalluded to in Enclosure 2,'Section:2.2.2 of. GL 88-17, if openings totaling greater. than 1l square inch exists in the cold legs, reactor coolant pumps'and crossover piping ofLthe RCS,tthe

core can uncover q'uickly when pressurized under loss of RHR conditions.

If this situation should arise, it is generally more effective to^ inject makeupf water into the hottleg rather than the cold. leg.

8.- You have not stated the use.of any specific' vent openings on'the' hot 1sidel of the'RCS to relieve RCS pressurization. The' removal'of a pressurizer .

manway or steam. generator.manway, for example,fis a.means to provide'RCS; venting. . Calculations'need~to be performed to. verify the effectiveness of RCS openings, however,Lbecause even for relatively large hot l 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. 1 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. 'We intend-to audit both your response _to the expeditious actions and your programmed enhancement program. The areasi where we do not fully understand your responses.as indicated above may be covered in the audit of expeditious actions.

2 This completes the staff review of your responses;to the expeditious actions l listed in the GL. The area of programmed enhancements will be addressed in.a-separate letter. 1 1

i Sincerely, I l

I

,, _Vm _ -

T ,

minic C. Dilanni, Project Manager 1

- Project Directorate III .

Division of Reactor. Projects?-LIII,.IV; V"

&'Special Projects

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L Office;of. Nuclear Reactor Regulation-PM/PD31:DRSP -

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