ML20150D510
| ML20150D510 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 03/18/1988 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20150D491 | List: |
| References | |
| NUDOCS 8803240310 | |
| Download: ML20150D510 (3) | |
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o UNITED STATES
}3 NUCLEAR REGULATORY COMMISSION
.t WASHINGTON, D. C. 20555 p'
ENCLOSURE 1 SAFETY EVALUATION BY THE CFFICE OF NUCLEAR REACTOR REGULATION t
GPU NUCLEAR CORPORATION j
PAIN STEAM LINE RUPTURE DETEC_TI,0N, SYSTEM l
THREE MILE ISLAND NUCLEAR STA110N Uh!T 1 DOCKET N0.,: 50-?89 10 BACKGROUND The Heat Sink Protection System (HSPS) includes the Main Steam Line Pupture Detection System (MSLRDS) as well as the Energency Feedwater System (EFWS).
i The staff issued Amendment No. 174 to the TMI-1 operating license and its final safety evaluation pertaining to the EFWS on March 9,1987, which closed FUREG-0737 item II.E.1.2 as an open issue for TMI-1.
This evaluation addresses the qualification of the MSLRDS automatic initiation signals and circuits.
The MSLRDS is designed to provide safety-grade initiation of Pain Feedwater (MFW) system isolation upon detecticn of Icw pressure in either of the Once Through Steam Generators (OTSGs). The MSLRDS is required to meet the relevant requirements of IEEE Std 279-1971. The licensee's April 29, 1985 response states that following completion of the long term modification to the Pain Steam Line Pupture Detection Circuitry portion of the EFWS, the system will be capable of withstanding a single active failure while still performing its function of initiating MFW isolation. These design modifications will also ensure that a single active failure will not inadvertently isolate the Main Feedwater (MFW) system.
2.0 DISCUSSION AND EVALUATION The initiating signals for the MSLRDS circuitry originate in the HSPS.
The HSPS is designed to initiate MFK' isolation on low pressure in either OTSG main steam line supply to the turbine PSLPDS is a two-out-of-four (2/4) generator.
The HSPS logic circuitry for the taken twice logic schete. There are fcur redundant instrufrentation channels for each OTSG that provide the HSPS logic with signals indicating low pressure in the OTSG steam lines. Two pressure measurement channels are connected to each of the two steam lines from each OTSG. The pressure transmitters are located such that two channel pressure transmitters for each OTSG are located in the Peactor Ruilding and the other two channel pressura transmitters for each OTSG are located in the Intermediate Building; this provides diversity of location. The actuation portion of the HSPS consists of two 2/4 logic traine for OTSG-A and two 2/4 logic trains for OTSG-B. The HSPS electronics will cause automatic isolation of the MFW to OTSG-A in the event of low pressure in the steam lines from OTSG-A and will l
8803240310 880318 PDR ADOCK 05000289 p
2 cause automatic isolation of the NFW to OTSG-E in the event of low pressure in j
the steam lines from OTSG-R unless the operator has bypassed one or both trains of the HSPS for the MSLPDS in accordarce with ncrtral sFutdewn procedures, in which case the MFW isolation by the HSPS will be bypassed.
The automatic initiation circuitry from the sensors to the HSPS circuitry for the MSLRDS and frem the HSPS to the Feedwater Isolation Valves was reviewed to deterrrine con.pliance with the single failure criterion of IEEE Std 279-1971.
It is concluded the automatic initiation circuitry complies with the single failure criterion of IEEE Std 279-1971.
The licensee has docuuented that the FSLRDS initiating circuitry and controls arr de.tigned with channel independence and redundency and that qualified istlatien devices have been incorporated into the design that will provide the required isolation for shared comon components of interfacing systems and non-IE equipment. Review of the EFWS design confimed that the criteria of charnel independence and of control and protection system interaction of IEEE Std 279-1971 have been met.
The licensee stated in a Farch 14, 1986 response that all devices in the MSLRDS automatic initiation circuitry can be tested at power. However, the pressure transmitters will only be tested at refueling intervals. All testing of the HSPS including the MSLRDS autorratic initiation circuitry, scnsors, and other associated equiptrent will be perfomed in accordance with technical specification requirerrents.
The criteria of paragraph 4.9 of IEEE Std 279-1971 require that means shall be provided for checking the operational availability of each system input senscr with a high degree of confidence during reactor operation.
In a telephone conversation on April 8,1987 to clarify how the licensee's design confoms to the criteria of Paragraph 4.0 and 4.10, the licensee stated that confomance to the criteria of Paragraph 4.9 is accortplished by cross-checking between channels that bear a known relationship to each other and have readouts available.
The licensee verified that the capability for calibrating channels and the devices used to derive the final system output signal from the various channel signals is included in the design.
The requirement to perform cross channel checks and calibration and the calibration frequency are included in the technical specificctions.
Prccedules to perform these checks and calibrations are in place. We concluded that the criteria of Paragraph 4.9 and 4.10 of IEEE Std 279-1971 have been met, i
The licensee has documented that the channel bypass capability requirements of paragraph 4.13 of IEEE Std 279-1971 have been incorporated into the design of the HSPS for automatic initieticr. of the emergency feedwater (EFW).
This capability permits any single operable channel to be maintained or tested at power with a single active failure in another channel. The PSPS contains an i
cperating bypass associated with the PSLRDS circuitry. This bypass is autorrati-cally removed when the steam line pressure increases above 750 psig and cannot be initiated whenever steam line pressure is greater than 750 psig.
Paragraph 4.13 of IEEE Std 279-1971 states that if the protecthe action of some part of the system has been bypassed or deliberately rendered inoperative for any purpose, this fact should be continuously ir.dicated in the centrol room.
i Section 3.3 of GPU's April 29, 1985 submittal states that when bypass occurs, l
an indicating light entitled "SLB ENABLED" will turn off indicating the PSLRDS has been bypassed.
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3 The criteria of paragraph 4.17 of IEEE Std 279-1971 specify that the protection system shall include means for marual initiation of each protective j
action at the system level.
In the April 8, 1987 telephone conversation, the licensee stated that the nanual initiation for NFW isolation is perfonned by four pushbuttons which cause valve closure when activated. The pushbuttens actuate closure of the rotor-operated valves and as a backup, the valve i
centroller units can be actuaied to assure isolaticn. This is acceptable.
As noted above, the TMI-1 design uses a bypass indicating light labeled "SLB ENABLED" which, when not lit, indicates that the NSLiiDS has been bypassed, i
The licensee's Human Factors Group has reviewed this light and has found it acceptable; however, they stated that requirir.g this light to be lit to indicate bypass status would be an enhancement.
By letter dated October 27, i
1987, the licensee has consnitted to provide positive indication for both bypass and enabled for each steam generator.
This will be accomplished by installing a tacklit pushbutton for (ach bypass and enable. The licensee comitted to nake these changes by the end of the cycle 8 refueling (approxi-mately January 1990) as part of n. ore extensive HSPS changes.
The staff finds j
these conr:itments an acceptable resolution, l
i Eased on the review of the TMI-1 MSLRDS, the staff concludes that the 1
automatic initiation circuitry complies with IEEE Std 279-1971. Specifically, the single failure criterion, calibration, channel independence and control and i
protection system interaction have been satisfied.
The staff finds the design of the MSLP.DS to be acceptable.
)
Cated:
Principal Contributor:
J. Stewart l
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