ML20055D086

Documents Deviation from Requirements of Reg Guide 1.97,per Insp on 900507-11.Based on Most Limiting Analysis,Existing Range of 0-1,200 Psi Sufficient.Deviation Consistent W/B&W Owners Group Task Force Evaluation of Reg Guide

ML20055D086
Person / Time
Site:	Three Mile Island
Issue date:	06/25/1990
From:	Hukill H GENERAL PUBLIC UTILITIES CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
RTR-REGGD-01.097, RTR-REGGD-1.097 C311-90-2077, NUDOCS 9007030192
Download: ML20055D086 (3)

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GPU Nuclear Corporation NUCIMr One Upper Pond Road Parsippany, New Jersey 07054 201-31 &7000 TELEX 136-482 Writers Direct Dial Number.

June 25,1990 C311-90-2077 U. S. Nuclear Regulatory Commission Attn Document Control Desk Washington, DC 20555 Gentlemen Three Mile Island Nuclear Generating Station, Unit 1 (TMI-1)

Operating License No. DPR-50 Docket No. 50-289 Conformance to Regulatory Guide 1.97 Steam Generator Pressure Instrumentation Range This letter documents a recently identified deviation from the requirements of

. Regulatory Guide 1.97 for steam generator pressure instrumentation range.

NRC Region I conducted an inspection from May 7 to May 11, 1990, to review the TMI-2 implementation program for Regulatory Guide 1.97 requirements. During this anspection it was identified that the steam generator pressure instramentation range provided did not fully comply with the requirements of Regulatory Guide 1.97. Regulatory Guide 1.97 specifies a Category 2 instrument with a range of 0 psig to 20% above the lowest safety valve setting for this parameter. THI-1 steam generator pressure instrumentation is Category 1 and has a range of 0-1200 peig, which is approximately 0 poig to 15% above the lowest safety valve setting. This instrument range was not identified as a deviation in the TMI-1 Evaluation of Compliance with Regulatory Guide 1.97 Requirements (GPUN letter 5211-86-2097, dated June 5, 1986).

THI-1 has an indication of main steam prresure at the turbine as well as at the outlet of the steam generators. These pressure indications are provided in the control room. The steam generator outlet pressures are typically measured over the range from 0-1200 psig. The NRC recommendation is for the range to be 20%

above the lowest safety valve settir.g. Since the lowest safety valve is set at 1040 psig, the' range would have to be on the order of 1250 psig to meet the NRC's recommendation. The following discussion is provided to justify that the existing range of 0-1200 psig is sufficient.

9007030192 900625 PDR O ADOCK 05000289 PDC 31014490 .

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! i Accident analyses performed for Midland indicate that for both the loss of external load transient and loss of all non-emergency AC power transient, the

, maximum steam pressure is 180 psi above the initial controlling steam pressure

of 885 pag. The resulting steam pressures at the steam generator outlet are typically 20-30 psi higher than at the turbine. This results in a maximum expected steam generator outlet pressure of 1085 to 1095 peig. The loss of electric load transient presented in the THI-l FSAR Chapter 14 does not analyze

, resulting steam pressures. However, the expected response is similar to the Midlaud FSAR accident analyses described above. The initial controlling steam pressure for TMI-1 is 895 psig at the turbine which results in maximum expected outlet pressures of 1095 to 1105 psig. Normal THI-1 post-trip steam pressures have been in the range of approximately 1060 psig to 1080 peig.

L The main steam lines are provided with safety relief valves, atmospheric dump

. valves (ADV) and turbine bypass valves (TBV) to prevent overpressurization of the lines, in.accordance with ASME Code Section III requirements. Operability of the main steam safety valves ensures that the secondary system pressure will  !

be limited to within code allowable pressuro during the most severe anticipated system operating transient. The highest main steam safety valve setpoint is 5%

above design. With a 3% accumulation to achieve full lift arid full flow, the maximum pressure while the main steam safety valves are relieving will be 8%

above the design pressure (1050 psig) which is less than 10% above the design pres sure, as specified by the ASME Code. This range is well within the indicated and accurate range for the THI-1 steam generator pressure instr.tmentation. THI-1 valve settings are indicated in the TMI-1 FSAR Section 10.7.4-i THI-1 has approximately 22% excess steam relief capacity when the plant is operating at ;-JO% Full Power and all main steam safety valves are operable k (without credit for the ADVs or TBVs). TMI-1 also has a main steam safety valve Technical Specification which limits the maximum allowable reactor power and thus steam flow, based on main steam safety valve operability. This will maintain that excess relief capacity.

Therefore, based on the fact that the highest safety valve setting is approximately 1092 poig, the steam relief captcity is approximately 22% above '!

the expected steam flow rate, and the me.t limiting analysis indicates a maximum steam pressure of about 1105 psig, it is concluded that the existing range of 0-1200 psig is sufficient.

In addition, the TMI-1 steam genorator pressure instrumentation is Category 1 for THI-1 and the pressure transmitters (PT-950, 951) are environmentally qualified.

The justification for this deviation from the instrument range requirements of Regulatory Guide 1.97, as described above, is consistent with the B&W Owner's Group Task Force evaluation of Regulatory Guide 1.97 variables as adopted by other B&W plants.

31014490

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HDH/DJD/py- .- . 11 Vice President and Director,~TMI-1 l

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