ML20153D356
| ML20153D356 | |
| Person / Time | |
|---|---|
| Issue date: | 04/02/1996 |
| From: | Charemagne Grimes, Wermiel J NRC (Affiliation Not Assigned) |
| To: | Burrows F NRC (Affiliation Not Assigned) |
| Shared Package | |
| ML20153D328 | List: |
| References | |
| NUDOCS 9809250037 | |
| Download: ML20153D356 (4) | |
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1 / UNITED STATES j
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NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 2056H001
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April 2. 1996 MEMORANDUM FOR:- Fr3derick H. Burrows 1
Electrical Engineering Branch Division of Engineering FROM: Christopher I. Grimes, Chief '
Technical Specifications Branch Associate Director for Projects ,._
Jared S. Wermiel, Chief Instrumentation and Controls Branch M I 6td Division of Reactor Controls and Human Factors
SUBJECT:
TECHNICAL SPECIFICATION REQUIREMENTS FOR INSTRUMENTATION AND CONTROL SYSTEMS i
In a memorandum dated March 6, 1996 you expressed concerns that your comments were not fully understood by those attending the meeting with the Westinghouse Owners Group on March 1, 1996, regarding the technical specifications (TS) practices for instrumentation and control (I&C) systems requirements. Your memorandum elaborated several related comments and attached a detailed discussion of the historical evolution of I&C requirements in TS.
Your concerns appear to arise from continued efforts to improve and simplify TS practices for I&C systems, which you believe have undermined earlier efforts (circa 1982) to satisfy the requirements of 10 CFR 50.36. These concerns are evident from your comments regarding the Vogtle and Beaver Valley Unit 2 five column format I&C TS, which you believe are representative of a thorough and technically complete approach to relate plarit TS, setpoint methodology, and the FSAR Chapter 15 analysis. Your comments also concluded that, while the use of instrument allowable values to determine past operability is acceptable, you indicate that channel trip setpoints must be reset within an acceptable band about the nominal trip setpoint, in order to ensure. future instrumentation TS operability. On this basis, you appear to conclude that the improved STS are technically deficient because of a lack of setpoint methodology detail.
You expressed particular concern that the use of allowable values for the loss of power diesel generator instrumentation is inadequate for Watts Bar TS (memorandum dated June 28, 1995 from B. W. Sheron to B. K. Grimes) and should be rewritten to clearly define trip setpoints and allowable values based on the guidance of Regulatory Guide 1.105 and ISA S67.04. However, we concluded that the allowable values in the Watts Bar TS, in conjunction with the staff's acceptance of the associated setpoint methodology, are adequate and satisfy the requirements of $50.36.
i We believe that the requirements for Limiting Conditions for Operation (LCO),
8 Safety Limits, Limiting Safety System Settings (LSSS), and Limiting Control 9809250037 900915 PDR TOPRP EMYWEST h C PM ,
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F. H. Burrows April 2. 1996 I
4 Settings in 10 CFR 50.36 may be satisfied with even less detail than is
, currently reflected in the improved standard technical specifications (STS).
- NUREG-1431, " Standard Technical Specificatf ons, Westinghouse Plants," contain
! only the allowable value and trip setpoint columns from the previous five j column format of the LC0 from prior versions of the Westinghouse STS.
We believe that the form of the requirements in NUREG-1431 establish a simpler
- approach that relates plant TS, setpoint methodology and the FSAR Chapter 15 analysis. The Bases in NUREG-1431 for reactor trip system instrumentation state that the trip setpoints are based on the analytical limits stated in the FSAR. A detailed description of the methodology used to calculate the trip setpoints is referenced in the STS Bases as the "RTS/ESFAS Setpoint
- Methodology Study." The Bases state that if the measured setpoint does not j- exceed the allowable value, the bistable is considered operable. The Bases further discuss that setpoints in accordance with the allowable value ensure
- that safety limits are not violated during off normal or accident conditions, providing the unit is operated from within the LCOs at the onset of these transients and the equipment functions, as designed.
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The NUREG-1431 trip setpoints are presented as limits, but can be used in
- conjunction with an appropriate setpoint methodology with nominal values at i which the bistables are set. Any bistable is considered to be properly
- adjusted when the "as left" value is within the band for channel calibration accuracy. The actual nominal trip setpoint is more conservative than that specified by the allowable value. Although the Bases in NUREG-1431 specify that the trip setpoints are the limiting safety system settings required by
$50.36, that designation was characterized as the licensing basis for 3- Westinghouse plants using Westinghouse setpoint methodology, but does not i reflect a consistent licensing basis for all plants.
i i The inconsistencies in the existing licens:ng basis for the I&C TS
- requirements in many plants, as is reflected partially in the detailed j historical description accompanying your memorandum as well as different opinions we have received from others, provide adequate reason to take this opportunity to clarify and simplify the TS requirements for I&C systems so i that they can be clearly understood by plant operators. The allowable values, i or some combination of allowable values and nominal setpoints, can readily j- satisfy the requirements of 150.36, although the Regulatory Guide and ISA
) Standards may need conforming changes to clarify the re htionship between the j Safety Limits, LSSS, LCSS. and the surveillance interv ; in TS. During the development of the improved STS, we were unable to obtain greater standardization in the I&C TS requirements because many licensees believed
]' that the NRC staff would require that their I&C procedures be backfit to a contenporary setpoint methodology. However, we believe that the existing j setpoint methodologies at all plants are not substantially different, and the
- procedures can be readily revised to use consistent definitions for the TS
) terms, if we could achieve consensus on those definitions.
The concerns in your memorandum are important considerations for ensuring that 1
I&C setpoint methodologies and related maintenance practices will achieve a I -, -- ~~ - - . . - . . _ - , - . - - _ -
. F. H. Burrows April 2. 1996 reliable safety function with adequate margin for the uncertainties associated with those practices. However, it is not clear that you have raised a particular technical concern or policy concern regarding the appropriate means to reflect those processes in TS requirements. If you have more specific concerns regarding the expression of setpoint methodologies in TS, or a particular-differing view regarding the course of action described above, we request that you document those concerns promptly so that they can be addressed before we attempt a revision to the Regulatory Guide and further improvements to the STS.
cc w/ incoming-R. Zimmerman B. Boger B. Sheron S. Varga J. Roe D. Crutchfield B. Grimes J. Calvo F. Hebdon
' TSB Staff HICB Staff 1
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. F. H. Burrows April 2, 1996 )
, reliable safety function with adequate margin for the uncertainties associated l with those practices. However, it is not clear that you have raised a particular technical concern or policy concern regarding the appropriate means to reflect those processes in TS requirements. If you have more specific concerns regarding the expression of setpoint methodologies in TS, or a particular differing view regarding the course of action described above, we request that you document those concerns promptly so that they can be addressed before we attempt a revision to the Regulatory Guide and further improvements to the STS.
cc w/ incoming R. Zimmerman B. Boger B. Sheron S. Varga l J. Roe D. Crutchfield i l B. Grimes l l J. Calvo l F. Hebdon TSB Staff l HICB Staff i DISTRIBUTION:
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