ML20238A211
| ML20238A211 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 08/31/1987 |
| From: | NORTHEAST NUCLEAR ENERGY CO. |
| To: | |
| Shared Package | |
| ML20238A122 | List: |
| References | |
| NUDOCS 8708200402 | |
| Download: ML20238A211 (4) | |
Text
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Docket No. 50-245 t
B12535 l
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i Millstonc Nuclear Power Station, Unit No. I Proposed Revision to Technical Specifications Reactor Protection System Trip Level Setting Changes l
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August 1987 8700200402 870817 PDR ADOCK 05000245 P
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' SAFETY LIMITS
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2.1.1 FUEL CLADDING INTEGRITY j
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When the reactor pressure is less than or equal to 800 psia or reactor-t flow is less than 10% of design, the reactor thermal power transferred to the coolant shall not exceed 25% of rated.
C.
1.
To assure that the Limiting Safety System Settings established in Specifications 2.1.2A and 2.1.2B'are not exceeded, each required scram shall be initiated by its primary source signal. The Safety l
Limit shall be assumed to be exceeded when scram is accomplished by a means other than the Primary Source Signal.
2.
When the process computer is out of service, this' safety limit shall i
be assumed to be exceeded if the neutron flux exceeds the scram setting established by Specification 2.1.2A and a control rod scram j
does not occur.
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D.
Whenever the reactor is in the cold shutdown condition with irradiated fuel in the reactor vessel, the. water level shall not be less than that corresponding to 12' inches above the top of the active fuel when it is seated in the core. This level shall be continuously monitored.
LTMITING SAFETY SYSTEM SETTINGS 2.1.2.A.1.a.
where:
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S=
Setting in percent of rated thermal power (2011 MWt)'
W=
Total recirculation flow in percent of.' design. See Note (1)
The trip setting shall not exceed 90 percent of rated power during generator load rejections from an initial reactor thermal' power greater than 50% of rated. The APRM scram setdown shall 1
be 90% of' rated within 30 seconds after initiation of full load rejection.
b.
In the event of operation with a maximum fraction of limiting power density (MFLPD) greater than the fraction of rated power (FRP), the setting shall be modified as follows:
- where,
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FRP = fraction of rated thermal power (2011 MWt)
Note (1) Design flog to'be defined as the recirculation flow (not to exceed 33.48 x 10 lbs/hr.) needed to achieve 100% core flow.
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Millstone Unit 1 2-3 1
j 2.1.2 FUEL CLADDING INTEGRITY
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BASES The design of the ECCS components to meet the above criteria was dependent on three previously set parameters:
the maximum break size, the low water 4
level scram setpoint, and the ECCS initiation setpoint. To lower the setpoint for initiation of the ECC5 would prevent the ECCS components from meeting their design criteria.
To raise the ECCS initiation setpoint would be in a safe direction, but it would reduce the margin established to prevent actuation of the ECCS during normal operation or during normally expected transients.
E.
Turbine Stop Valve Scram The turbine stop valve scram, like the load rejection scram, anticipates I
the pressure, neutron flux, and heat flux increase caused by the rapid closure of the turbine stop valves and failure of the bypass. With a scram setting of < 10% of valve closure, the resultant increase in surface heat flux is limited such that MCPR remains above 1.07 even during
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the worst case transient that assumes the turbine bypass is closed. This scram is bypassed when reactor thermal power is less than 50% of rated.
I F.
Turbine Control Valve Fast Closure The turbine control valve fast closure scram is provided to anticipate the rapid increase in pressure and neutron flux resulting from fast closure of the turbine control valves due to a load rejection and subsequent failure of the bypass; i.e., it prevents MCPR from becoming less than 1.07 for this transient. For the load rejection from 100% power, the heat flux increases to only 106.5% of its rated power value, which results in only a i
small decrease in MCPR. This trip is bypassed below a reactor thermal power of 50% of rated because, below this power level, the MCPR is greater than 1.07 throughout the transient without the scram.
In order to accommodate the full load rejection capability, this scram trip must be bypassed because it would be actuated and would scram the reactor during load rejections. This trip is automatically bypassed for a maximum of 280 millisec following initiation of load rejection.
After j
280 millisec, the trip is bypassed providing the bypass valves have opened.
If the bypass valves have not opened after 280 millisec, the bypass is removed and the trip is returned to the active condition. This j
bypass does not adversely affect plant safety because the primary system pressure is within limits during the worst transient even if the trip fails. There are many other trip functions which protect the system during such transients.
G.
Main Steam Line Isolation Valve Closure Scram f
i The low pressure isolation of the main steam lines at 825 psig was provided to give protection against rapid reactor depressurization and the resulting rapid ecoldown of the vessel.
Advantage was taken of the scram feature which occurs when the main steam line isolation valves are closed, Millstone Unit 1 B 2-8 n
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