ML20012C477

Responds to Generic Ltr 89-19, Request for Action Re Resolution of USI A-47, 'Safety Implication of Control Sys in LWR Nuclear Power Plants,' Per 10CFR50.54(f). Current Design Adequate W/O Addl Tech Specs

ML20012C477
Person / Time
Site:	Three Mile Island
Issue date:	03/12/1990
From:	Hukill H GENERAL PUBLIC UTILITIES CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
REF-GTECI-A-47, REF-GTECI-SY, TASK-A-47, TASK-OR C311-90-2031, GL-89-19, NUDOCS 9003220026
Download: ML20012C477 (4)

Text

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=e 5' J OPU Nuclear Corporation

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.. ggIgf - Post Office Box 480 Route 441 South

> Middletown, Pennsylvania 17057 0191 '

717 944 7621' TELEX 84 2M6 Writer's Direct Dial Number:

March 12, 1990 C311-90-2031-U.'S.< Nuclear Regulatory Commission

-Attn: Document Control Desk Washington, DC 20555

Dear Sir:

Three Mile Island Nuclear Station, Unit 1 (TMI-1)

Operating License No. DPR-50 Docket No.'50-289 GPUN Response to-NRC. Generic Letter 89-19 NRC Generic Letter (GL) 89-19, " Request for. Action Related to Resolution'of. Unresolved Safety Issue A-47 ' Safety Implication of Control = Systems in LWR Nuclear Power Plants Pursuant to 110 CFR 50.54 (f)" requested: licensees to provide a statement as to

'whether certain recommendations will be implemented and if not to provide justification. The GL recommended-that licensees of B&W

-plants provide automatic steam generator overfill protection and

'that plant procedures and technical specifications include provisions to. verify periodically the operability of-the overfill.

' protection and to assure that.au'omatic overfill protection is available to mitigate main-feedwater overfeed events during power operation.

Once:Through Steam Generator (OTSG) overfill-protection for TMI-1 is provided by the Heat Sink ProtectionLSystem (HSPS). The HSPS provides automatic initiation of Emergency Feedwater (on OTSG Low

-Level,1 Loss of Both Main Feedwater (MFW) Pumps, or High Reactor Building Pressure) and MFW isolation-(on OTSG Low Pressure or OTSG High Level). Technical Specifications that apply to the HSPS do not include the OTSG high level MFW isolation feature.

< Operating procedures and surveillance tests assure adequate

. maintenance and use of the equipment including the overfill

protection feature. This letter provides GPUN's justification forethe adequacy of the current design and procedures without additional technical specifications.

Attachment 1 describes TMI-l's MFW overfill protection provided by the OTSG high level MFW isolation portion of the HSPS.

-Attachment 2 describes the surveillance test program that GPUN thas applied which will assure its reliability.

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GPU Nuclear Corporation is a subsidiary of the General Public Utilities Corporation k\ \

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3 C311-90-2031 March 12, 1990 1 GPUN believes that automatic overfill protection provided for TMI-1 resolves an economic concern rather than a safety concern and that more stringent operability requirements, if imposed, would unnecessarily increase the likelihood of Loss of Feedwater (LOFW) events without a commensurate safety benefit. s Prior to startup following the installation of the HSE's in 1987, GPUN completed a safety evaluation which examined er.1 cor.flemed the acceptability of temporarily operating with the nigh OTSG level MFW isolation signal bypassed. This evaluatiuu was  ;

reviewed and accepted by B&W and the NRC staff at that time.

GPUN has recently updated this safety evaluation to address the concerns expressed by the NRC in GL 89-19 and to address a letter from B&W dated February 5, 1990 which also recommended the addition of overfill protection systems for plants that do not have them. .GPUN's updated safety evaluation describes the analysis performed and TMI-l's operating procedures for coping with overfill events and confirms the validity of the conclusions drawn earlier. The revised safety evaluation is available at the site for NRC review.

Sincerely, H. D. Hukill Vice President and Director, TMI-1 HDH/MRK Attachments cc: J. Stolz F. Young R. Hernan TP. Martin >

Swornandsubscribegj~to /d beforeof day meYdM this/G , 1990.

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RW f-Shamn P. Brown, Pubre

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h. PommyMola Aenocueon of M

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Attachment 1-Descriotion of TMI-l's OTSG Overfill Protection System f

Once Through Steam Generator (OTSG) overfill protection for TMI-1 is provided by the Heat Sink Protection System (HSPS). The Integrated Control System (ICS) limits MFW flow during plant operation based on high OTSG level via the control action of the i

MFW control valves. .The HSPS provides separate overfill protection for each OTSG by closing all MFW control and block valves on OTSG high level.

The'HSPS monitors level in each OTSG by four channel sensors (transmitters). Level switches (bi-stables) associated with these sensors feed redundant Train A and Train B coincidence logic. Each train's coincidence logic is 2 out of 4. Each train of HSPS overfill protection closes the motor-operated block valves of one OTSG and the MFW control valves of the other OTSG.

Neither the ICS nor the HSPS trip the MFW pumps.

The HSPS is separate from the ICS in terms of power source and location. The ICS MFW control and HSPS overfill protection '

circuits are separately routed to the extent that class 1E signals are separated from non-class 1E signals.

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9 Attachment 2 TMI-1 Surveillance Proaram for the Overfill Protection System

, l The following is a list of the surveillance procedures

• that' verify the operability and calibration of the OTSG high level MFW .

isolation feature of the HSPS: )i Weekly: l l

e Surveillance Checks (1301-4.1) 1 j

Comparison check of each OTSG's four operating range levels.- 1 Quarterly:

e OTSG Level and Pressure Channel Tests (1303-11.37A-D)

One point calibration tests of the operating level loop and high level isolation bistable setpoints for each channel.

'This procedure verifies each channel from the transmitter output to the remote indicators and to the 2 out of 4 logic

-train input.

o Main Feedwater Isolation Logic Test (1303-11.38)

Checks the logic for each train to verify that 2 out of 4 high level channel isolation signals will initiate a MFW isolation signal to the MFW valve' isolation logic.

Refueling:

e OTSG Level and Pressure Channel Calibrations (1302-5.26)

Full calibration of the OTSG operating level loop from the transmitter to the indicators. This procedure verifies calibration of the-analog level loop to the bistables.

e Main Feedwater Isolation Check ~(1302-5.35)

Logic tests to verify that a MFW isolation signal from either train will shut the corresponding MFW valves.

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• These surveillance procedures were written to comply with TMI-1

l. Technical Specification (TS) Table 4.1-1, " Instrument 1 Surveillance Requirements." Item no. 51 of the table specifies L the check, test, and calibration requirements for the HSPS l .(including the MFW Isolation on OTSG Low Pressure and the four EFW automatic initiation features). The MFW Isolation on High OTSG level feature of the HSPS is included in these surveillance procedures because typically the complete instrument loop is y checked or calibrated even though some part of the loop may not be TS required.

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