TXX-6852, Interim Deficiency Rept CP-87-104 Re Possible Errors in Protection Actuation Setpoints Calculations.Initially Reported on 870914.Effect of Actual Measuring Test Equipment Inaccuracies to Be Determined.Next Rept by 880118
| ML20236H801 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 10/14/1987 |
| From: | Counsil W TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| CP-87-104, TXX-6852, NUDOCS 8711040358 | |
| Download: ML20236H801 (2) | |
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Ref 0 10CFR50.55(e) l h
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October 14, 1987 x
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l U. S. Nudlear Regulatory Commission
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1 Attn: Document Control Desk-Washington, D. C. '20555-
SUBJECT:
COMANCHE PEAK STEAM EtECTRIC STATION (CPSES)
DOCKET N05. 50-445 AND 50-446 SAFETY SYSTEM SETPOINT CALCULATION ERROR SDAR: CP-87-104 (INTERIM REPORT) m)
LGentlemen:-
i On September 14,L 1987, we verbally notified your Mr. H. S. Phillips of.a deficiency' involving possible errors ~in protection actuation setpoint calculations for NSSS systems.
This is an interim r'e
. reportable item under the provisions of 10CFR50.55(e) port of a potentially t
' Specifically,'during the preparation of the protection actuation setpoint calculations for the NSSS Systems, no allowance for calibration inaccuracies was included in the calculations. These conditions were apparently due to an assumption made by the equipment supplier (Westinghouse) that the accuracy of the measuring and test equi) ment (M & TE) would be greater than the accuracy of the equipment being cali) rated by a factor of ten.
This assumption was j
based on SAMA Standard PMC-20-1-1973 entitled " Process Management and Control Tenninology. " Section 4.2 of the SAMA standard states that if the accuracy of the M & TE is ten times greater than the equipment being calibrated, l
inaccuracies of M & TE do not need to be considered.
Unless the " ten times" accuracy factor for M & TE is followed or an allowance for.M & TE inaccuracies is included in the calculations, a reduction in'the Limiting Safety System setpoint margin could result This condition would-affect the following setpoints:
1.
Containment Pressure Hi-1, Hi-2, Hi-3 2.
Pressurizer Pressure Low SI 3.
RWST Low Level 4.
N-16 Overtemperature j
The M & TE utilized during the actual calibration had an occuracy equal to or greater than the equipment being calibrated.
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In order to evaluate the safety significance of this condition, the ef fect of
~ the actual M & TE inaccuracies on the calculated safety niargin of these setpoints will be determined.
i Our next report on this issue will be submitted no later than January 18, 1988.
Very truly yours,
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f9 7to W. G. Counsil i
1 VIP /grr 1
c - Mr. R. D. Martin, Region IV i
Resident Inspectors, CPSES (3)
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