ML17257A392
| ML17257A392 | |
| Person / Time | |
|---|---|
| Site: | PROJ0728 |
| Issue date: | 09/25/2017 |
| From: | Rowley J Licensing Processes Branch (DPR) |
| To: | Peters G AREVA |
| Rowley J | |
| References | |
| CAC MF6753 | |
| Download: ML17257A392 (8) | |
Text
September 25, 2017 Mr. Gary Peters, Director Licensing and Regulatory Affairs AREVA Inc.
3315 Old Forest Road Lynchburg, VA 24501
SUBJECT:
REQUEST FOR ADDITIONAL INFORMATION REGARDING AREVA INC.
TOPICAL REPORT ANP-10337P, PWR FUEL ASSEMBLY STRUCTURAL RESPONSE TO EXTERNALLY APPLIED DYNAMIC EXCITATIONS (CAC NO. MF6753)
Dear Mr. Peters:
By letter dated August 31, 2015 (Agencywide Documents Access and Management System Accession No. ML15266A250), AREVA Inc. (AREVA) submitted for U.S. Nuclear Regulatory Commission (NRC) staff review and approval Topical Report ANP-10337P, PWR [Pressurized Water Reactor] Fuel Assembly Structural Response to Externally Applied Dynamic Excitations.
Upon review of the information provided, the NRC staff has determined that additional information is needed to complete the review. On July 17, 2017, Jerald Holm, AREVA Product Licensing Manager, and I agreed that the NRC staff will receive the response to the enclosed request for additional information (RAI) questions by October 31, 2017.
If you have any questions regarding the enclosed RAI questions, please contact me at 301-415-4053.
Sincerely,
/RA/
Jonathan G. Rowley, Project Manager Licensing Processes Branch Division of Policy and Rulemaking Office of Nuclear Reactor Regulation Project No. 728
Enclosure:
RAI Questions
ML17257A392; *concurred via e-mail NRR-106 OFFICE PLPB/PM PLPB/LA* SNPB/BC PLPB/BC PLPB/PM NAME JRowley DHarrison RLukes DMorey JRowley DATE 9/14/17 9/21/17 9/8/17 9/11/17 9/25/17 REQUEST FOR ADDITIONAL INFORMATION RELATED TO TOPICAL REPORT ANP-10337P PWR FUEL ASSEMBLY STRUCTURAL RESPONSE TO EXTERNALLY APPLIED DYNAMIC EXCITATIONS AREVA INC.
RAI-1
Describe the seismic methodology for reactor cores comprised of mixed-vendor cores in a revision to the topical report (TR) (ANP-10337). This request for additional information (RAI) is requesting AREVA Inc. (AREVA) to provide change pages to the TR that will fully describe and discuss the methods, procedures, and modifications to the standard methodology that are necessary when modeling mixed-vendor cores. The changes to the TR should include differences in model damping, model finite element representation, and explain how vendor-specific test protocols affect the model construction.
RAI-2
The gaps between spacer grids and neighboring grids and baffle plates are defined precisely in Equations 5-7, 5-8, and 5-9. These equations do not include terms to update gaps according to accumulated plastic grid deformation. Justify the application of this methodology in cases where accumulated plastic deformation of spacer grids exceeds dimension tolerance. Propose and justify a grid deformation limit for this analysis methodology.
RAI-3
Hydrodynamic coupling is an important feature of the modeling methodology, but information on the topic is not consolidated in the TR to the same extent that the other modeling topics are documented. This RAI requests AREVA to enhance the discussion of hydrodynamic coupling in the TR or to respond to this RAI with a consolidated explanation of hydrodynamic coupling and how it is modeled in the methodology. Details should include definitions and procedures for defining added water mass and the implementation of hydrodynamic coupling force. If this RAI is to be addressed in the TR, provide change pages for review.
RAI-4
Provide a model sketch similar to Figure 5-7 of the TR that identifies the model parameters (i.e.,
gapped spring stiffness, gapped damper coefficient, etc.) discussed in Section 6.2.3.1.
RAI-5
NRC requested AREVA to supply high priority information to help advance the technical review prior to conducting the May 2017 audit. AREVA provided information electronically to address the following audit questions. This RAI requests AREVA to document the response to each of the following audit questions:
Enclosure
- 38. (Appendix A) Identify which version of CASAC is to be used with this methodology.
Provide the latest Validation and Verification (VnV) reports on the version of CASAC intended to be used with this methodology. Provide the VnV model input files, including CASAC input files and any ANSYS input files used to generate comparison results, on a DVD or external hard drive. This is a general request for VnV material that supports the current version of CASAC, including material that may exist but was not referenced in the TR.
- 39. (Appendix A.1.1) This section lists 15 verification problems. Provide documentation of the verification problem results. Provide the CASAC model input files on a DVD or external hard drive. If the verification problems were compared to ANSYS (as was done in BAW-10133 for CASAC Version 4.1) provide the ANSYS model input files on a DVD or external hard drive.
- 40. (Appendix A.1.2) The CASAC 4.1 Validation Report provided in BAW-10133 Addendum 1 included seven verification problems that compare CASAC results to theoretical results and ANSYS results. The current TR does not include these specific verification problems and does not mention any comparison to ANSYS. Run the seven validation cases of the CASAC 4.1 Validation Report on the version of CASAC intended to be used in this methodology and compare them to ANSYS. Provide an updated validation report for the current version of CASAC (CASAC X.X). Provide the CASAC and ANSYS model input files on a DVD or external hard drive.
- 43. (Appendix B.3) Provide electronic core plate motions for the example problem described in Appendix B, on a DVD or external hard drive. Comma delimited ASCII files
(*.CSV) of core plate motion data would be ideal.
RAI-6
Define amplitude as it is used throughout the TR. Is it consistent in the TR and all supporting data? Peak-to-peak or single-sided? How is amplitude defined in the case of a free vibration pluck test? How does amplitude compare to the maximum deflection calculated in the horizontal CASAC models?
RAI-7
Fixing the horizontal fuel assembly model stiffness to [' '''''''''' ''''''''' ''''''''' '''''''''
'''''''''''''''''' '] instead of modeling the stiffness as a [''''''''''''''' ''''''''''''''''''' ''''' '''''''''''''''' '' '''''
'''' '''''''''''''''' ''''''''' '''' '''''''''''''''''''']. The model is essentially a ['''' '''''''' '''''''''''''''''''''''''' '
''''''''''''' '' '''''''''''''' ''''' ''' '''''']. When the fuel assembly model deflects [''''''' '
''''' ''''' '''' ''''''''''''''''''''''], the error between the model prediction and the real expected behavior of the fuel assembly deflection grows. This error can be related to the elastic energy stored in the model at a given imposed deflection. Plot the elastic energy contained in the model of Appendix B ['''''''''''' ''] over a range of first mode deflections from zero to 150 percent of the maximum gap stack-up. Then [''''' ''' ''''''''' '''''' '''' '''''''] and plot the elastic energy curves over the same range of first mode deflections. It is necessary to consider 150 percent of the maximum gap stack-up to account for grid elastic compression. It is also
necessary to consider beginning-of-life (BOL) and end-of-life (EOL) conditions. Provide the energy versus deflection curves and use them to justify the [] benchmark proposed in the TR.
RAI-8
Section 6.1.1.2 of the TR states: Forced vibration tests can be used in lieu of free vibration tests for fuel assembly dynamic characterization for overlapping ranges of amplitudes. Clarify the intent of this sentence. Is the methodology proposing that free vibration tests can be replaced by forced vibration tests?
RAI-9
The sample problem provided in the TR Appendix B provides a reasonable example of the application of the methodology but the loading conditions are relatively weak compared to the guide tube stress and grid impact force. This RAI requests AREVA to create an additional sample problem that increases the lateral seismic loads to approach the limits of the guide tube stress and grid impact force. It is anticipated that the only changes to the sample problem will be a set of revised core plate motions. Document the results of this new sample problem, identify any other changes to the model documented in Appendix B, and provide the new core plate motions as digital data.
RAI-10
Section 5.3.1.1 of the TR states: The transient hydrodynamic forces are the primary driver of the fuel assembly response. In cases where the core plate motions are shown to be negligible, this modeling of the core plates can be simplified to a rigid, stationary plate.
- Clarify how core plate motions are shown to be negligible. What is to be done when they are not negligible?
- Clarify how plant specific licensing bases affect the availability of vertical motion.
- Clarify how the methodology will treat cases when vertical motion is not available.
- Confirm the methodology will adopt this limitation: If vertical motion is not available, an explanation is required on a case-by-case basis.
Revise the TR to provide the requested clarification and confirm the limitation regarding a lack of vertical core plate motion. Provide change pages.
RAI-11
The detailed procedure for defining the grid impact parameters appears to permit grid buckling below the allowable crushing load (PACL) as long as the buckling takes place outside dimension tolerances. Is this the intent of the procedure or should the procedure state: PACL is never greater than buckling load, Pcrit?
RAI-12
Regarding Section 6.2.2.1 of the TR, explain how grid slip load (a force) is related to the material modulus.
RAI-13
Regarding Section 6.1.3.2 of the TR, clarify the damping [''''''''''''''''''''''''''] proposed to be used during loss of offsite power (LOOP). Address the following points:
- [''''''''''' '' ''''''''''''''''''''''''' ''''''''''''''''''' ''''''' '''''''''''' ''' '''''''''' ''''''''''''''' '''''' '''''''''' '
'''''' ' '' '' '''' ''''' '' ''''''''''' '' '''''''''''''' '' ''''''''''' '''''''].
- ['''''''''''' ''' '''''''' ''''' ''''''' ''''''''''''' ''''''' '' ''''''''''''''''''''''''''].
- ['''''''''''' ''' '''''''''' '''''''''' ' '' ''''''''''''''''''''''''''' ' '' '''''''' ''''''''''''' '' '''''' ''''' '
''''''''''''' ''''''' ''''''''''']
- [''''' ''''''''''''' '' ''''''''' '''''''''' ''' ''''''''''''''''''''''' ''''' '' ''''''''''' ''''''''' ''''''''''''
''''''''''''' '''''''''''''''''''''''''].
- [''''''''''' ''''' '''''''''' ''''' '' ''''''''''''''''''''''''' '''''''''''''''''''''''' ''''''''' ''''''''''''''' ''''''''' '''''
''''''''''''''''''' ''''''''''''''''''' '''''' '''''' ' ''' ''''''''''''''''''''''''''].
RAI-14
Figure D-13 of the TR shows a ['''''''' '''''''''''''''''''' '''''''''''''''''''' ''''' '''' ''''''''''''' ''''''''''''''
''''''''''''''' ' ''''' '''''''''''' '''''''''''''''''''''''' '''''''''''].
RAI-15
Section 4 of the TR defines grid spacer acceptance criteria in the form of allowable plastic deformation for an operating basis earthquake and safe shutdown earthquake (SSE) plus loss-of-coolant accident (LOCA) (or LOCA alone). No maximum allowable permanent grid deformation is described for SSE-alone. Identify and justify the maximum allowable permanent grid deformation that the analysis methodology supports. Alternatively, provide a new methodology for justifying the maximum allowable permanent grid deformation under SSE-alone loads. As part of the response, describe the impact of permanent grid deformation on (1) local thermal-hydraulic conditions and departure from nucleate boiling calculations and (2) the performance of safety-related structures, systems and components to prevent or mitigate the consequences of accidents that could result in potential offsite exposures. Provide change pages to the TR.
RAI-16
AREVA typically checks the ['''''''''''''' ' '''' ''''''''' ''''' ''''' ''''''''''''''''] using the coefficient of determination, R2, but does not have an acceptance criteria. Identify and justify R2 acceptance criteria for [''''' '''''''''' ''''''''''''''''' ''''' ' '''''''''''''''''''''' ''''''''] to be modeled in the methodology.
RAI-17
Clarify the use of the ['''''''''''''''''''''' '''''''' ''''''' '''''''''''''''']. The TR suggests that rotational springs are used in all cases, but [''''''''''''''''''''''''' ' ''' '''''''' ''''''''''''''' ''' '''''''''''''']. Clarify the use of rotational springs and the ['''''''''''''''''''''''''' ''''''''' ''''''''' ''''''''''''']. Identify and justify error limits for tuning the model to the target mode frequencies.
RAI-18
Clarify the process for determining the limiting deflection case for evaluation of non-grid component stresses. Explain how ['''''''''''''''''' '''''' ''''''''''''''''' ''''' '''''''''''''''''''' '''''''' '''''''''''']
are used to find the most limiting deflection shape.
RAI-19
A number of minor error corrections and clarifications were identified at the May 2017 audit.
Provide change pages for any necessary corrections and clarifications.
RAI-20
The methodology is proposing to use new stress-based control rod insertability criteria. Guide tube stresses are calculated according to the methodology described in the TR and are compared to the insertability criteria. If the stresses meet the insertability criteria then control rod insertion is ensured. The technical basis for the insertion criteria is contained in an internal AREVA document, ['''''''''''''''''''''''''''''''''''''], which includes experimental testing and analysis related to inserting control rods into permanently deformed guide tubes.
- Provide a summary of ['''''''''''''''''''''''''''''''''].
o Include a summary of the materials and geometry of the guide tubes and control rods that were investigated with insertion testing.
o Include a summary of the set of deformation shapes that were evaluated during insertion testing.
o Include a summary of the magnitude of deformations performed in testing and relate them to American Society of Mechanical Engineers Boiler and Pressure Vessel Committee stress limits (primary membrane (Pm) and primary membrane plus bending (Pm+Pb)).
o Include a summary of the geometric constraints in the core that limit the magnitude of deformation.
o Include a summary of the relationship between guide tube deformation and control rod insertion times.
o Did the testing and analysis consider three-dimensional guide tube deformation?
- Section B.3.3.3.2 of the TR proposes different definitions for minimum strength (Sm) in non-irradiated and irradiated conditions. This indicates different guide tube deformation
levels are being proposed for non-irradiated and irradiated conditions. Explain how this was accounted for in the testing and analysis documented in ['''''''''''''''''''''''''''''''''''''''].