ML20006G205
| ML20006G205 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 02/22/1990 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML20006G202 | List: |
| References | |
| NUDOCS 9003050338 | |
| Download: ML20006G205 (2) | |
Text
e I/4.6 CONTAINMENT SYSTEMS BASES 3/4. 6.1 PRIMARY CONTAINMENT 3/4. 6.1.1 CONTAINMENT INTEGRITY Primary CONTAINMENT INTEGRITY ensures that the release of radioactive materials from the containment atmosphere will.be restricted to those leakage paths and associated leak rates assumed in the safety analyses.
This restriction, in conjunction with the leakage rate limitation, will limit the site boundary radiation doses to within the limits of 10 CFR 100 during accident conditions.
3/4. 6.1. 2 CONTAINMENT LEAKAGE The limitations on containment leakage rates ensure that the total containment leakage volume will not exceed the value assumed in the safety analyses at the peak accident pressure of 38 psig P. As an a
added conservatism, the measured overall integrated leakage rate is during perfonnance of the periodic tests further limited to < 0.75 La,dation of the containment leakage barriers to account for possTble degra between leakage tests.
The surveillance testing for measuring leakage rates are consistent l
with the requirements of 10 CFR Part 50, Appendix J with the following exemption.
The third test of each Type A testing set need not be conducted when the plant is shutdown for the 10-year plant inservice inspections.
The operational readiness of the vessel is considered proven by the ILRT, and in accordance with license requirements, when completed per the 401 10 months frequency.
The special test for the containment purge and exhaust isolation valves is intended to detect gross degradation of seals on the valve seats. The special test is performed in addition to the Appendix J requirements.
3/4.6.1.3 CONTAINMENT AIR LOCKS The limitations on closure and leak rate for the containment air lo:ks are required to meet the restrictions on CONTAINMENT INTEGRITY and containment leak rate. Surveillance testing of the air lock seals provide assurance that the overall air lock leakage will not become g-excessive due to seal damage during the intervals between air lock
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leakage tests.
DAVIS-BESSE, UNIT 1 B 3/4 6-1 Amendment No. H,146
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i CONTAINMENT SYSTEMS t
BASES I
3/4.6.1.4 INTERNAL PRESSURE i
The limitations on containment internal pressure ensure that 1) the containment structure is prevented from exceeding its design negative pressure differential with respect to the annulus atmosphere of 0.5 psi and 2) the containment peak pressure does not exceed the design pressure of 40 psig during LOCA conditions.
The maximum peak pressure obtained from a LOCA event is 37 psig.
The limit of 1 psig for initial positive containment pressure will limit the total pressure to 38 psig which is less than the design pressure and is consistent with the safety analyses.
i 3/4.6.1.5 AIR TEMPERATURE f
The limitations on containment average air temperature ensure that l
the overall containment average air temperature does not exceed the initial temperature condition assumed in the accident analysis for a LOCA.
3/4.6.1.6 CONTAINMENT VESSEL STRUCTURAL INTEGRITY s
This limitation ensures that the structural integrity of the contain-ment steel vessel will be maintained comparable to the original design standards for the life of the facility.
Structural integrity is required to ensure that the vessel will withstand the maximum pressure of 38 psig in the event of a LOCA. A visual inspection in conjunction with Type A leakage tests is sufficient to demonstrate this capability.
3/4.6.1.7 CONTAINMENT VENTILATION SYSTEM The limitation on use of the Containment Purge and Exhaust System limits the time this system may be in operation with the reactor coolant system temperature above 200*F. This restriction minimizes the time that a direct open path would exist from the containment atmosphere to the outside atmosphere and consequently reduces the probability that an accident dose would exceed 10 CFR 100 guideline values in the event of a LOCA occurring coincident with purge system operation. The use of this system is therefore restricted to non-routine usage not to exceed 90 l
i hours in any consecutive 365 day period which is equivalent to approximately 1% of the total possible yearly unit operating time.
3/4.6.2 DEPRESSURIZATION AND COOLING SYSTEMS j
3/4.6.2.1 CONTAINMENT SPRAY SYSTEM i
The OPERABILITY of the containment spray system ensures that contain-ment depressurization and cooling capability will be available in the event of a LOCA.
The pressure reduction and resultant lower containment DAVIS-BESSE, UNIT 1 B 3/4 6-2 Amendment No.135
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