ML20058E637
| ML20058E637 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 10/29/1990 |
| From: | NORTHEAST NUCLEAR ENERGY CO. |
| To: | |
| Shared Package | |
| ML20058E633 | List: |
| References | |
| NUDOCS 9011070252 | |
| Download: ML20058E637 (2) | |
Text
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Docket No. 50-336 B13664 1
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-Millstone Unit No. 2 Technical Specification Bases Changes 1
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October 1990 90110~70252 901029 f,M ADoCK 0500o336 PDC
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3,7 -
4 LIMITING SAFETY SYSTEM SETTINGS a
BASES Thermal Marain/ Low Pressure (Continued)
The trip is. initiated whenever.the reactor coolant system. pressure signal
-drops below either 1850 psia or a computed value as described below, whichever-L
.is. higher..-The computed value is a function of the higher of AT power or 1
neutron power, reactor inlet temperature,.the number of reactor coolant pumps operating and the AXIAL SHAPE INDEX. The minimum value of reactor coolant J
flow rate, the' maximum AZIMUTHAL POWER TILT and the maximum CEA deviation permitted.for continuous operation are assumed in the generation of this trip
. function..In addition, CEA group sequencing in accordance with Specifications 3.1.3.5 and 3.1.3.6 is assumed.
Finally, the maximum insertion of CEA banks
.which can occur during any anticipated operational-occurrence prior to a-Power i
Level-High. trip is assumed.
Thermal: Margin / Low Pressure trip setpoints are derived from the core t
' safety limits through application of appropriate allowances for equipment l
response time measurement uncertainties-.and processing error.
A safety margin
.is provided which includes:. an allowance of 5% of RATED THERMAL POWER to compensat.e-for potential power measurement error; an allowance.of 2*F to compensate.for potential temperature measurement uncertainty; and a further allowance of'74 psi to compensate for. pressure measurement error, trip system l
processing-error, and time delay associated with providing effective termina-tion of the occurrence that exhibits the most rapid decrease in margin to the -
safety limit.' The 74. psi. allowance is made up of a 5 psi bias, a 19 psi l
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pressure measurement allowance and a 50 psi time delay allowance.
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. Loss of Turbine
- A' Loss of Turbine trip causes a direct reactor trip when operating above i
15% of RATED THERMAL. POWER.- This trip provides turbine protection, reduces the severity of the' ensuring transient and helps avoid the lifting of the main R
steam line safety valves during the ensuing transient, thus extending the service life of these values. No credit was taken in the accident analyses for operation of this trip.- Its functional capability at the specified trip setting is required to enhance the overall reliability of the Reactor Protec-tion System, i
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MILLSTONE - UNIT 2 B 2-7 Amendment No. 3, A2, 139
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