ML20216C351
| ML20216C351 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 03/09/1998 |
| From: | NORTHEAST NUCLEAR ENERGY CO. |
| To: | |
| Shared Package | |
| ML20216C350 | List: |
| References | |
| NUDOCS 9803130382 | |
| Download: ML20216C351 (4) | |
Text
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Docket No. 50-423 B17000 Millstone Nuclear Power Station, Unit No. 3 Marked Up Technical Specification Page March 1998 9803130382 980309 PDR ADOCK 05000423 P
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O REACTOR COOLANT SYSTEM BASES
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DVERPRESSURE PROTECTION SYSTEMS (continued) temperature overpressure transient. Setting both valves to the values of Figure 3.4-4a and Figure 3.4-4b within the tolerance allowd for the calibration accuracy, ensures that the Reference I limits will not be exceeded for the analyzed isothermal events.
When a PORV is opened, the release of coolant will cause the pressure increase to slow and reverse. As the PORY releases coolant, the RCS pressure decreases until a reset pressu're is reached and the valve is signaled to close.
The I
pressure continues to decrease below the reset pressure as the valve closes.
RHR Suction Relief Valve Reauirements j
The isolation valves between the RCS and the RHR suction relief valves must be open to make the RHR suction relief valves OPERABLE for RCS overpressure mitigation. The RHR suction relief valves are spring loeded, bellows type water relief valves with setpoint tolerances and accumulation limits established by Section III of the American Society of Mechanical Engineers (ASME) Code (Ref. 3) for Class 2 relief valves.
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When the RHR system is operated for decay heat removal or low pressure letdown control, the isolation valves between the RCS and the RHR suction relief valves are open, and the RHR suction relief valves are exposed to the RCS and are able to relieve pressure transients in the RCS.
RCS Vent Reauirements Once the RCS is depressurized, a vent exposed to the containment atmosphere will maintain the RCS at containment ambient pressure in an RCS overpressure transient, if the relieving requirements of the transient do not exceed the capabilities of the vent. Thus, the vent path must be capable of relieving the flow resulting from the limiting mass or heat input transient, and maintaining pressure below the P/T limits for the analyzed isothermal events.
For an RCS vent to meet tha finw caoacity requirement, it requires removino a Draecurizer safety valve,S_:xte: : ^^"Y : d di::::::: it: tu;
=!r S th: )
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- iti:Q removing a Pressurizer manway, or similarly establishing a vent py opening an RCS vent valve provided that the opening meets the size requirements. The vent path must be above the level of reactor coolant, so as not to drain the RCS when open.
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MILLSTONE - UNIT 3 B 3/4 4-17 Amendment No.157 one
Docket No. 50-423 B17000 Millstone Nuclear Power Station, Unit No. 3 Retyped Technical Specification Page i
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t I
l March 1998
l l
l BASES OVERPRESSURE PROTECTION SYSTEMS (continued) l temperature overpressure transient. Setting both valves to the values of Figure 3.4-4a and Figure 3.4-4b within the tolerance allowed for the calibration accuracy, ensures that the Reference 1 limits will not be exceeded for the analyzed isothermal events.
When a PORV is opened, the release of coolant will cause the pressure increase to slow and reverse. As the PORV releases coolant, the RCS pressure decreases until a reset pressure is reached and the valve is signaled to close.
The pressure continues to decrease below the reset pressure as the valve closes.
Rh' Suction Relief Valve Reauirements The isolation valves between the RCS and the RHR suction relief valves must be open to make the RHR suction relief _ valves OPERAf>LE for RCS_ overpressure mitigation. The RHR suction relief valves are spring loaded, bellows type water l
relief valves with setpoint tolerances and accumulation lim'ts established by Section III of the American Society of Mechanical Engineers (ASME) Code (Ref. 3) for Class 2 relief valves.
When the RHR system is operated for decay heat removal or low pressure letdown control, the isolation valves between the RCS and the RHR suction relief valves l
are open, and the RHR suction relief valves are exposed to the RCS and are able to relieve pressure transients in the RCS.
I l
RCS Vent Reauirements l
Once the RCS is depressurized, a vent exposed to the containment atmosphere will l
maintain the RCS at containment ambient pressure in an RCS overpressure l
transient, if the relieving requirements of the transient do not exceed the i
capabilities of the vent. Thus, the vent path must be capable of relieving the flow resulting from the limiting mass or heat input transient, and maintaining l
pressure below the P/T limits for the analyzed isothermal events.
For an RCS vent to meet the flow capacity requirement, it requires removing a Pressurizer safety valve, removing a Pressurizer manway, or similarly l establishing a vent by opening an RCS vent valve provided that the opening meets the size requirements. The vent path must be above the level of reactor coolant, i
so as not to drain the RCS when open.
4 MILLSTONE - UNIT 3 B 3/4 9-17 Amendment No. #7, 0674