ML23205A222

Response to Sdaa Audit Question A-6.2-3

ML23205A222
Person / Time
Site:	99902078, 05200050
Issue date:	07/24/2023
From:	NuScale
To:	Office of Nuclear Reactor Regulation
Shared Package
ML23205A216	List: ML23205A217 ML23205A218 ML23205A219 ML23205A220 ML23205A222 ML23205A223 ML23205A224 ML23205A225 ML23205A226 ML23205A227 ML23205A228 ML23205A230 ML23205A231 ML23205A232 ML23205A233
References
LO-146777
Download: ML23205A222 (1)

Text

NuScale Nonproprietary Response to SDAA Audit Question Question Number: A-6.2-3 Receipt Date: 05/08/2023 Question:

SDAA Section 6.2.1.3.5 (Description of the Long-Term Cooling Model) states that the containment response analyses demonstrate that the CNV pressure and temperature rapidly reduce and remain at acceptably low levels following postulated mass and energy releases, including LOCA, into the containment. NuScale DSRS Section 6.2.1.1.A, Acceptance Criteria 2 states that to satisfy GDC 38 to rapidly reduce the containment pressure, the pressure should be reduced to less than 50 percent of the peak calculated pressure within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after the postulated design basis accident. SDAA Figure 6.2-7 shows that for the limiting CNV pressure DBA, the CNV internal pressure reaches its peak of 937 psia at 170 sec, and then decreases to about 690 psia (74% of the peak) around 1400 sec. The figure does not show the CNV pressure reducing to less than 50% of peak pressure (~468 psia) within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, as mandated by the Acceptance Criteria 4. Figure 6.2-7 needs to be updated to demonstrate that the GDC 38 requirement is met.

Response

Figure 6.2-7 below shows the limiting containment pressure case extended for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, with the reactor pool temperature boundary condition maintained at 140 F. The containment pressure is less than 50% of the peak pressure within a few hours after the break occurs and remains acceptably low. This figure has been updated in the SDAA.

Markups of the affected changes, as described in the response, are provided below:

NuScale Nonproprietary

NuScale US460 SDAA NuScale Final Safety Analysis Report Audit Question A-6.2-3 Figure 6.2-7: Maximum Containment Internal Pressure - Peak Containment Vessel Pressure Case



6.2-76 Draft Revision 1 Containment Systems