ML022560434
| ML022560434 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 09/05/2002 |
| From: | Stephen Monarque NRC/NRR/DLPM/LPD2 |
| To: | Christian D Virginia Electric & Power Co (VEPCO) |
| References | |
| TAC MB3530, TAC MB3531 | |
| Download: ML022560434 (4) | |
Text
Contai nment 3.6 CONTAINMENT SYSTEMS 3.6.4 Containment Pressure LCO
3.6.4 APPLICABILITY
Containment air partial pressure shall be within the acceptable operation range shown on Figure 3.6.4-1.
MODES 1, 2, 3, and 4.
ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME A.
Containment air A.1 Restore containment 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> partial pressure not air partial pressure within limits, to within limits.
B.
Required Action and B.1 Be in MODE 3.
6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> associated Completion Time not met.
AND B.2 Be in MODE 5.
36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> SURVEILLANCE REQUIREMENTS SURVE ILLANCEFRQEC SR 3.6.4.1 Verify containment air partial pressure is 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> within limits.
Amendment Nos.
232/214 North Anna Units 1 and 2 Dressure 3.6.4 3.6.4-1
Containment Pressure 3.6.4 Ranges*
Containment Temperature 86-120"F RWST Temperature < 50"F I( ).e a, i 1
- 1.
35 40 45 50 55 60 65 70 75 80 85 90 95 100 Service Water Temperature (F)
Figure 3.6.4-1 (page 1 of 1)
Containment Air Partial Pressure Versus Service Water Temperature Amendment Nos.
232/214 North Anna Units 1 and 2 120 11.5
"*, 110 U, 105 S100
- 0.
S95 E
90 90 0
U 8.5 80 3.6.4-2
Conta1 nmen APPLICABLE SAFETY ANALYSES (continued)
The maximum design internal pressure for the containment is 45.0 psig. The LOCA analyses estaolish the limits for the containment air partial pressure operating range. The initial conditions used in the containment design basis LOCA analyses were an air partial pressure of 11.7 psia and an air temperature of 1200F. This resulted in a maximum peak containment internal pressure of 44.1 psig, which is less than the maximum design internal pressure for the containment.
The containment was also designed for an external pressure load of 9.2 psid (i.e., a design minimum pressure of 5.5 psia). The inadvertent actuation of the QS System was analyzed to determine the reduction in containment pressure (Ref.
1). The initial conditions used in the analysis were 8.43 psia and 1207F. This resulted in a minimum pressure inside containment of 7.07 psia, which is considerably above the design minimum of 5.5 psia.
For certain aspects of transient accident analyses, maximizing the calculated containment pressure is not conservative. In particular, the cooling effectiveness of the Emergency Core Cooling System during the core reflood phase of a LOCA analysis increases with increasing containment backpressure. For the reflood phase calculations, the containment backpressure is calculated in a manner designed to conservatively minimize, rather than maximize, the containmentpressure response in accordance with 10 CFR 50, Appendix K (Ref.
2).
Containment pressure satisfies Criterion 2 of 10 CFR 50.36(c) (2) (01).
LCO Maintaining containment pressure within the limits shown in Figure 3.6.4-1 of the LCO ensures that in the event of a DBA the resultant peak containment accident pressure will be maintained below the containment design pressure. These limits also prevent the containment pressure from exceeding the containment design negative pressure differential with respect to the outside atmosphere in the event of inadvertent actuation of the QS System. The LCO limits also ensure the return to subatmospheric conditions within 60 minutes following a DBA.
Amendment Nos.
232/214 North Anna Units 1 and 2 BASES P-essure B 3.6.4 I
B 3.6.4-2
RS System B 3.6.7 BASES BACKGROUND cooling tank. The casing cooling pumps are considered part (continued) of the outside RS subsystems. Each casing cooling pump is powered from a separate ESF bus.
The RS System provides a spray of subcooled water into the upper regions of containment to reduce the containment pressure and temperature during a DBA.
Upon receipt of a High-High containment pressure signal, the two casing cooling pumps start, the casing cooling discharge valves open, and the RS pump suction and discharge valves receive an open signal to assure the valves are open. After a 400+/-5 second time delay, the inside RS pumps start, and after a 210+/-5 second time delay, the outside RS pumps start.
The RS pumps take suction from the containment sump and discharge through their respective spray coolers to the spray headers and into the containment atmosphere. Heat is transferred from the containment sump water to service water in the spray coolers.
The Chemical Addition System supplies a sodium hydroxide (NaOH) solution to the RWST water supplied to the suction of the QS System pumps.
The NaOH added to the QS System spray ensures an alkaline pH for the solution recirculated in the containment sump. The resulting alkaline pH of the RS spray (pumped from the sump) enhances the ability of the spray to scavenge iodine fission products from the containment atmosphere. The alkaline pH of the containment sump water minimizes the evolution of iodine and minimizes the occurrence of chloride and caustic stress corrosion on mechanical systems and components exposed to the fluid.
The RS System is a containment ESF system. It is designed to ensure that the heat removal capability required during the post accident period can be attained. Operation of the QS and RS systems provides the required heat removal capability to limit post accident conditions to less than the containment design values and depressurize the containment structure to subatmospheric pressure in < 60 minutes following a DBA.
The RS System limits the temperature and pressure that could be expected following a DBA and ensures that containment leakage is maintained consistent with the accident analysis.
North Anna Units 1 and 2 Amendment Nos.
232/214 B 3.6.7-2