ML20098C112
| ML20098C112 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 09/29/1995 |
| From: | CENTERIOR ENERGY |
| To: | |
| Shared Package | |
| ML20098C108 | List: |
| References | |
| NUDOCS 9510060251 | |
| Download: ML20098C112 (3) | |
Text
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'Page'9 REACTOR COOLANT SYSTEM SAFETY VALVES AND PILC' OPERATED RELIEF VALVE - OPERATING-UMITINGCONDITIONFOROPERATION 3.4.3 All ressurizer code safety valves shall be OPERABLE with a lift-setting of.
2626 )sig.* When not isolated. the pressurizer pilot operated re ie@f) valve s1all have a trip setpoint of 2 2435 psig and an 4
allowable value of 22435 psig.**
' APPLICABILITY: MODES 1, 2 and 3.
ACTION:
. ith one pressurizer code safety valve inoperable, either restore the inopera-W ble valve to OPERABLE status within 15 minutes or be in HOT SHUTDOWN within 12
. hours.
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SURVEILLANCE REQUIREMENTS 4.4.3 For the pressurizer code safety valves, there are no additional Surveillance Requirements other than those required by S)ecification 4.0.5.
For the pressurizer pilot operated relief valve a CHANNE_ CALIBRATION check shall-be performed every 18 months.
The lift setting pressure shall-correspond to ambient conditions of the valve at nominal operating temperature and pressure.
Allowable value for CHANNEL CALIBRATION check.
fDAVIS-BESSE UNIT 1 3/4 4-4 Amendment No.33.60.I28.I25 9510060251 950929 PDR ADOCK 05000346 P _.
. _.,_ _ EDR.., _, _
l.dx-TS PAGE PROVIDED 3/4.4
- REACTOR COOLANT SYSTEM BASES 3/4.4.1 REACTOR COOLANT LOOPS The plant is designed to operate with both reactor coolant loops in operation, and maintain DNBR above the minimum allowable DNB ratio during all normal operations and anticipated transients. With one reactor coolant pump not in operation in one loop, THERMAL POWER is restricted by the Nuclear Overpower Based on RCS Flow and AXIAL POWER IMBALANCE, ensuring that the DNBR will be maintained above the minimum allowable DNB ratio at the maximum possible THERMAL POWER for the number of reactor coolant pumps in operation or the local quality at the point of minimum DNBR equal to the DNB correlation quality limit, whichever is more restrictive.
In MODE 3 when RCS pressure or temperature is higher than the decay heat removal system's design condition (i.e. 330 psig and 350'F), a single The reactor coolant loop provides sufficient heat removal capability.
remainder of MODE 3 as well as in MODES 4 and 5 either a single reactor coolant loop or a DHR loop will be sufficient for decay heat removal; but single failure considerations require that at least two loops be OPERABLE.
Thus, if the reactor coolant loops are not OPERABLE, this specification requires two DHR loops to be OPERABLE.
Natural circulation flow or the operation of one DHR pump provides adequate flow to ensure mixing, prevent stratification and produce gradual reactivity changes during boron concentration reductions in the Reactor The reactivity change rate associated with boron reduc-Coolant System.
tion will, therefore, be within the capacity of operator recognition and control.
3/4.4.2 and 3/4.4.3 SAFETY VALVES The pressurizer code safety valves operate to prevent the RCS from being pressurized above its Safety Limit of 2750 psig.
Each safety valve is designed to relieve 336,000 lbs per hour of saturated steam at the valve's setpoint.
The relief capacity of a single safety valve is adequate to relieve any overpressure condition which could occur during shutdown.
In the event that no safety valves are OPERABLE, an operating DHR loop, connected to the RCS, provides overpressure relief capability and will prevent RCS overpressurization. During operation, all pressurizer code s'afety valves must be OPERABLE to prevent the RCS from being pressurized above its safety limit of 2750 psig. The combined relief capacity of all of these valves is greater than the maximum surge rate resulting from any transient.
The relief capacity of the decay heat removal system relief valve is adequate to relieve any overpressure condition which could occur during shutdown.
In the event that this relief valve is not OPERABLE, reactor coolant system pressure, pressurizer level and make up water inventory is limited and the capability of the high pressure injection system to DAVIS-BESSE, UNIT 1 B 3/4 4-1 Amendment No. 33,38,57,92,728,149
LAR 94-0010 Page 11 3/4.4 REACTOR COOLANT SYSTEM BASES inject water into the reactor coolant system is disabled to ensure operation within. reactor coolant system pressure - temperature limits.
Demonstration of the safety valves' lift settings will occur only during shutdown and will be performed in accordance with the provisions of Section XI of the ASME Boiler and Pressure Code.
The pressurizer code safety valves must be set such that the peak Reactor Coolant System pressure does not exceed 110% of design system pressure (2500 psig) or, 2750 psig.
The control rod group withdrawal accident will result in the most limiting high pressure in the RCS. The analysis assumes RPS high
. pressure trip at 2355 psig and the code safety valves open at 2500 psig.
The is 30 and-it is [3% 44 for the
. tolerance on the RPS instrument accura '
us 1]
valvesegins.
l code safet
.s i
Vie ~hressurizer p1 opera re TE va ve was assume o open f5F this transient. The
~
resultin stem eak sure was calculated to be 2710 3700 gg
^fli erETore. FIecoesifefy"
~556 at < 2575 2626
@ggggpjfy3],g_@tjg{r1@g,psig)JlMh hB10E9Bff3@l$19-qqu (se toler-p@sig! which is 33j3ppesstire op}if is conserva;1ve va ve_s,e n
500 R
anceg[gm the t
,4j The pressurizer pilot operated relief valve should be set such that it will open before the code safety valves are opened. However, it should not open on any anticipated transients.
BAW-1890. September 1985 identified that the turbine trip from full power would cause the largest overpressure transient.
This report demonstrated that with a RPS high pressure trip setpoint of 2355 psig the resulting overshoot in RCS pressure would be limited to 50 psi.
Consequently, the minimum PORV setpoint needs to accommodate both the RCS pressure overshoot and the RPS instrument string error of 30 psi.
DAVIS-BESSE. UNIT 1 B 3/4 4-la Amendment No. 33.60 I28,I25