ML24215A135
| ML24215A135 | |
| Person / Time | |
|---|---|
| Site: | 05200050 |
| Issue date: | 08/02/2024 |
| From: | NuScale |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML24215A000 | List:
|
| References | |
| LO-169995 | |
| Download: ML24215A135 (1) | |
Text
{{#Wiki_filter:Response to NuScale Technical Report Audit Question Question Number: A-5.PTLR-14 Receipt Date: 10/20/2023 Question: NuScale provided EC-107452 R1 in response to audit Questions A-5.PTLR-2, 3, 4, and 5. Based on the information provided in EC-107452 R1: Page 102: 3.5.1.3 - Please provide a high-level description of the overall analytical approach. Specifically, please confirm or correct the following description of the analytical approach: (1) The 2-Dimensional (2D) 1000 psi calculation was just to identify limiting locations, and a different pressure could have been chosen. (2) the 3-Dimensional (3D) 1 psi model is to calculate stress-intensity factor (SIF) coefficients and then scale up as function of actual applied stress via linear superposition. A follow-up question was received on December 5, 2023:
The response did not clarify how the Kim value would be scaled proportionally. Follow-up question received on January 19, 2024:
The response about not needing to scale KIm/p is acceptable. However, the staff disagrees that the equation KImp=MmxRit is equivalent to the equation KIm=MmxRit. Specifically, these two equations are only equivalent at one point: p=1psi. The equivalence cannot be generalized. The equation should be written as: KImpp=1psi=MmxRit, which means KImp=1psi=MmxRit So, the inequality in the response to PTLR-14 should be corrected to NuScale Nonproprietary NuScale Nonproprietary
p<KIc-KIt2KImp=1psi Equations 3-14, 3-15, and 3-16 in the SDAA should be corrected such that KIm is replaced by (KIm)p=1psi
Response
Original Response: The basis for determining allowable pressure is specified in ASME Section XI Non-mandatory Appendix G, Paragraph G-2215. The requirement to be satisfied shall be: 2+ < The above criteria is rearranged using substitution to solve for allowable pressure as follows.
Noting
=
= Constant at a given location and flaw orientation. This is a linear equation whereby the output divided by the input is constant. Requirement of ASME Section XI Non-mandatory Appendix G, Paragraph G-2215 then becomes. 2
+ <
2
2
In this specific analysis, is determined using a pressure of 1 psig. Therefore, the basis criteria as it applies to the methodology outlined by TR-130877 can be rewritten as: NuScale Nonproprietary NuScale Nonproprietary
2 =1 The following outlines the high level approach on how the above parameters are obtained to determine the allowable pressure.
- 1) Section 3.3.2 of TR-130877-P identifies critical regions of the RPV as the most limiting regions for both thermal and pressure stress locations. The two-dimensional (2D) model uses the thermal transients to identify the critical time point and global locations for thermal stresses. The 2D model uses an internal pressure of 1000 psi to identify both global and local critical locations for pressure stresses.
- 2) For the critical locations identified in item 1, the 2D thermal transient analysis:
a) determines the temperature at the crack tip required for calculating the critical stress intensity factory (SIF) measuring fracture toughness (KIC), as described in Section 3.3.3.3 and Equation 3-1 of TR-130877-P. b) determines the 3rd order polynomial coefficients (c0, c1, c2, c3,) for calculation of SIFs due to thermal stress (KIT), as described in Section 3.3.3.4.2 and Equation 3-7 of TR-130877-P.
- 3) For the critical locations identified in item 1, the three-dimensional (3D) pressure (1-psig) application model:
a) singularly simulates critical location flaws with no other flaws present. b) calculates the maximum SIF (KIm) due to internal pressure for one loadstep in the analysis (p = 1 psi), as discussed in Section 3.3.3.4.1 and Equation 3-2 and Equation 3-5 of TR-130877-P. KIm/psi in this analysis is a constant equal to Mm x Ri/T. I does not require scaling to determine allowable pressure. c) calculates the SIFs due to transient thermal stresses (KIt_c0, KIt_c1, KIt_c2, KIt_c3) by superposition, as discussed in Section 3.3.3.4.2 and Equation 3-10 of TR-130877-P.
- 4) NuScale uses the results of items 1 through 3 above to calculate the following parameters:
a) the maximum SIF (KIT) for any axial or circumferential surface crack inside or outside the RPV b) the RPV allowable pressures for preservice hydrostatic testing, normal heatup and cooldown transients, and inservice leak and hydrostatic testing conditions, as Section 3.3.3.5 of TR-130877-P describes. Revision 2 of EC-107452 is in the electronic reading room (eRR) in response to audit question A-5.PTLR-18. NuScale Nonproprietary NuScale Nonproprietary
Response to NRC Follow-up Question received on December 4, 2023: NuScale and the NRC discussed the follow-up question on December 11, 2023. The NRC noted that there should be a p term in Equation 3-13 of TR-130877-P. NuScale noted that p is equal to 1 psi, so Equation 3-13 did not include the pressure term. The markups to TR-130877-P attached to this response add the pressure term to Equation 3-13 in TR-130877-P and include a clarification that p = 1 psi. Response to NRC Follow-up Question received on January 19, 2024: The inequality in the original response to audit question A-5.PTLR-14, 2 has been revised to:
2 =1 Equations 3-13 through 3-16 in TR-130877-P, Pressure and Temperature Limits Methodology, have been revised to replace Klm/1 psi with (Klm/p)p = 1 psi. Markups of the affected changes, as described in the response, are provided below: NuScale Nonproprietary NuScale Nonproprietary
Pressure and Temperature Limits Methodology TR-130877-NP Draft Revision 1 © Copyright 2024 by NuScale Power, LLC 27 Audit Question A-5.PTLR-14, Audit Question A-5.PTLR-17 The allowable pressure associated with a specified temperature along a P-T limits curve is: Eq. 3-13 The appropriate and values used for various conditions are:
For preservice hydrostatic tests, a steady-state condition ( ) is applied, and the required structural factor Audit Question A-5.PTLR-14, Audit Question A-5.PTLR-17 Eq. 3-14 Performance of the allowable pressure calculation occurs for the crack with highest that bounds other cracks. The basis for the preservice limiting pressure is NUREG-0800, Section 5.3.2 (Reference 6.1.4). For the heat up and cooldown transients, the thermal SIF calculation occurs at selected time points, and the required structural factor Audit Question A-5.PTLR-14, Audit Question A-5.PTLR-17 Eq. 3-15 For ISLH, the SIF from heat up and cooldown transients conservatively apply to the most limiting crack, and the required structural factor Audit Question A-5.PTLR-14, Audit Question A-5.PTLR-17 Eq. 3-16 3.3.4.6 10 CFR 50, Appendix G, Pressure and Temperature Limits Appendix G of Reference 6.1.3 requires that the P-T limits are at least as conservative as limits obtained by following the Appendix G of Reference 6.1.5, methods presented in Section 3.3.4.5. Additionally, Table 1 of Appendix G of Reference 6.1.3 requires further limitations (Table 3-3). P KIC KIT ( )t SF Mm Ri
KIC KIT SF KIm p
( )p 1 = psi
= = KIT SF KIT 0 = SF 1 = P KICt Mm Ri
KIC KIm p
( )p 1 = psi = = Mm KIT SF 2 = P KIC KIT ( )t 2Mm Ri
KIC KIT 2 KIm p
( )p 1 = psi = = KIT SF 1.5 = P KIC KIT ( )t 1.5Mm Ri
KIC KIT 1.5 KIm p
( )p 1 = psi = =}}