ML19095B767
| ML19095B767 | |
| Person / Time | |
|---|---|
| Site: | PROJ0728, 99902041 |
| Issue date: | 10/24/2017 |
| From: | Rowley J NRC/NRR/DLP/PLPB |
| To: | Peters G Framatome |
| Rowley J, NRR/DLP, 415-4053 | |
| Shared Package | |
| ML19095B761 -Pkg. | List: |
| References | |
| ANP-10332P, Rev. 0, CAC MF3829 | |
| Download: ML19095B767 (37) | |
Text
REQUEST FOR ADDITIONAL INFORMATION RELATED TO TOPICAL REPORT ANP-10332P, REVISION 0, AURORA-B: AN EVALUATION MODEL FOR BOILING WATER REACTORS; APPLICATION TO LOSS OF COOLANT ACCIDENT SCENARIOS AREVA INC.
RAI-1
Please clarify the following statement on Page 4-3 of Topical Report (TR) ANP-10332P:
Provided that the licensing basis of the plant does not significantly depart from the SRP
[Standard Review Plan bases, the AURORA-B LOCA [loss-of-coolant accident] EM
[evaluation model] supports the licensing basis of each plant to which it is applied by analyzing the plant-specific scenarios, consistent with the criteria defined in the licensing basis documents for the plant.
How would AREVA determine if a licensing basis has significantly departed from the SRP bases? What if a departure occurs? Provide relevant examples.
RAI-2
On Page 6-21 of ANP-10332P, Table 6-1 ['''''''''''''''''' '''''''''' ''''''''''' ''''''''''' '''''''''''''''' '''''''
'''''''''''''''''''']. Please confirm this information is beyond the intended scope of the TRs application or justify its inclusion.
RAI-3
How do the predictions of the proposed AURORA-B LOCA EM compare to those of the existing approved EM for the spectrum of BWR loss-of-coolant accidents (LOCAs)? Please provide comparison cases using similar initial conditions for a large- and a small-break LOCA scenario.
RAI-4
Please correct the apparently misstated sentence on Page 4-8 or justify that it is correct:
[''''''''''''''''''''' ' '''' ''''' '''''''''' ''''''''''''''' '' '''''''''' ''''''''''''''''' '''' ''''''''''''''''''''' '''''' '''''''''''''
'''''''''' '''''' ''' ''''''''' '''''].
Enclosure
Clarify whether the intended meaning is:
['''''''''''''''''''' ' '' ''''' '''''''''' '''''''''''''' '' ''''''''' ''''''''''''''' '''' '' ''''' ''''''' ''''''''''
'''''''''''' ''''' ''''''''''''' '''''''''' ''''''''' ''' ''''''''' ''''''''''''' ''''' ''' ''''''''' ''''].
RAI-5
ANP-10332P presents a single phenomenon identification and ranking table (PIRT) for the spectrum of postulated LOCA events. The PIRT and accompanying textual descriptions appear to focus [''''''''''' '''''' ''''''''''''''''' ''''''''''''''' ' '''''' '''''''''''''''''''''' '''' ''''''']. Whereas, the importance of PIRT phenomena may vary substantially depending upon the location and size of the piping rupture, as well as the plant type. Furthermore, [''' '''''''''''''''''''''''''''''' '''''''''''''''''
'''''''''' ''''''' ' ''''''''''''' ''' ''''''''''' '''''''''''''''''' '' ''''''' ''''''' '''''''']. In light of the discussion above, please provide the following information supporting development of the PIRT in ANP-10332P:
- a. Please clarify how AREVAs PIRT process considered the full range of possible LOCA break locations and sizes, such that confidence exists that all applicable phenomena have been captured and appropriately ranked. If ['''''''''''''' ''''''''' ' '''''''''''''''' ''''''''
''''''''' ''''' '''''''''''''' '''''''''' '' ''''''''' '''''''''''''''' '''''''' ''''''''' '''''''''''''''''''''''' '''''''''']
were used to develop the PIRT in Table 4-1 of ANP-10332P, then please provide these documents.
- b. Please provide an analogous discussion to part a. regarding how the full range of BWR plant types was considered in the PIRT.
- c. What method is used to determine overall ranking in cases of disagreement between phenomenon rankings for LOCAs of different break location, break size, or plant type?
RAI-6
Section 6.3.3 of ANP-10332P states that the primary thermal-hydraulic, thermal conduction, and neutron kinetics processes and closure relations for modeling highly ranked PIRT phenomena are summarized in Table 6-3 of the TR. However, the [''''''''''''''''' '''''''''''''''' ''' '''''' ''''''''' '
'''''''' '''' ''''' '''' '''''''''''''''''''''''' '''''''''''''''''''' '''''''' ''''] is unclear and should be documented such that the NRC staff can be confident that AREVA has fully accounted for all important physical phenomena and processes associated with the spectrum of postulated BWR LOCA events. If all highly ranked PIRT items in ['''''''' ''' '' '' ''''''' '''''''''''''' '''' '''
''''''' ' ''''''''''''' '' ' ''''] of ANP-10332P, then please provide justification.
RAI-7
Please clarify the following issues concerning items in the PIRT:
- a. Explain the meaning of PIRT item [''''''''''''''''''''''''' '''''''''''''''''''''' '''' ''''''''''''''' '''''''''
'''''' ''''''''''''''''' '''''''''''']. Please further explain why this item is ranked low for refill and reflood. [ '' ''''''' ''''''''' '''''''''' ''''''' ' '''''''' ''''''' '''' ''''' '''' ''''''''''' ''''''
''''''''''''''''''''' '''' '''''''' '''''' '''''''' '''''' ''''''''''''''''''''' ' '' '''' ''''' ''''''''''' ''''''''''''].
- b. Explain specifically the flowpath or flowpaths referred to by PIRT item [''''''''''''''
''''''''''''''''''''' ''''''''']
- c. The ranking for ['''''''''''''''''''''''''' ' '''''''''' '''' ''''''' ''''''''' ' ''''], but the rationale for importance states [''''' '''''' ' ''''''''''''''''''' '' '' '''''''''''''''''' '''''''''' ''''''
'''''''''''''''''''''''''''' ''''' ''''''''''''''' ''''''''''']. Please clarify this apparent contradiction.
- d. Explain why [''''''''' ''''' ' '''''''' ''''''''''''' ' ''''''''''' '''''' '' '' ''''' '''' ''''''''''''
''''' '''''' ' ' ''''''''''' ''''''''''''']?
- e. Provide justification for [''''''''''' ' ''''''''' ''''''''''''''''''''''''''''' ' '''''' ''''''''''' '''''''' '''''
''''''''''''''''''' ''''''''''''''''''''' '''' ''''''''''''''''''''''].
- f. Although Section 5.4.6 of ANP-10332P discusses ['''''''''' ''''''''''''''''' ''''''''' '''''''''
''''''''''''''''''''''''''''''''''' '''''''''''].
RAI-8
Please clarify whether it is necessary to validate and assess any ['''''''''''''''''''''''''''' '''''''''''''''''''''
''''' ''''''''''''''''''''''''' ' '''''''''''''''''''''''''''''''''' '''''''''''''''''''''' '''' '' ''''''''''''' ' '' '''''''''''''' ''''''].
RAI-9
How is the pressure drop associated with recirculation pumps modeled in AURORA-B for both forward and reverse flow, and what is the technical basis? Furthermore, regarding Item II.3 in Appendix K, please clarify whether sensitivity analyses have been performed that are sufficient to determine a generically limiting condition with respect to whether a recirculation pump that has coasted down should be assumed to freespin or become locked in place?
RAI-10
During an audit held on May 16-18, 2017, AREVA stated its intention [ '''''''''''' ''' '''''
''''' '''' ''''''' ''''''''''''' '''''' '''''''' '' '' '' ''' '' ''''''''''''''''''''''' ''''''''''' ''''].
RAI-11
Please describe the modeling of fuel pellet thermal conductivity in RODEX4 as a function of exposure and summarize the basis for concluding that the concerns raised in Information Notice 2009-23 have been adequately addressed.
RAI-12
In light of the facts that (1) the S-RELAP5 code contains a kernel taken from the RODEX4 code,
[' ''''''''' ' ''''''''''''''''' ''''''' '''''''''''' ''' ''''''''' ''''' ''' '' '''''''''''''''''' '''''''' ' ''
'''''''''''''''''''' ''''''''''''''''''''' '''''' ''' '''''''''''''''''''''' ''''''''' ''']. If AREVA does not agree to such a commitment, please provide an alternative approach with adequate justification.
RAI-13
The AURORA-B LOCA EM incorporates a kernel of routines from the RODEX4 code (Reference 9 of ANP-10332P) into S-RELAP5 to calculate ['''''''''''''' ''''''''''''''''''''''''''''''''''''''''' ''''
'''''] The following questions seek to clarify the coupling between the RODEX4 kernel and the master code, S-RELAP5.
- a. Explain the guidance and justification [' '' ''''''''''''''''''''''''''''' '''''' ''''''''''' ''''''''''''''' ''
'''''''''''''''''''].
- b. How does RODEX4 account for the effect of cladding and fuel dimensional changes (e.g., thermal expansion, creep, cladding swelling/rupture, etc.) in the calculation of gap conductance?
- c. In calculating an [''''''''''''''' ''''' ''''''''''''''''''''''''''''], how does RODEX4 account for the non-uniformity of the fuel-cladding gap size in the axial and azimuthal directions?
- d. Fuel pellet ['''''''''''''' ''''''''''''''''''''' ' '''''''''''''' ''''''''''' ''''''''''''''''''''' '''''''''''''''''''' '''''''''''''''''
''''''''''' ''''''''''''''' ''''''' '''' ''''' ' ''''''' '' '''' ''''''''''''''' '''''''''''''''''']. Explain the impact of the timing of this change in fuel thermal conductivity on the conservative prediction of peak cladding temperature (PCT) for time-in-life LOCA analyses of different break sizes.
RAI-14
The NRC staff has previously reviewed a number of aspects of the AURORA-B LOCA EM for other applications.
- a. Please highlight and, as necessary, either cite or provide justification for [''''''' '''''''''''''''''
'''''''''''''''''''''''' '''''''''''''''''''''' ''''' '''''''''''''''''''].
- b. Please identify and justify the [''''''' ''''''''''''''' ''''''''' '''''''''''''''''' '' '''''''''''''''''''' ''''''
'''''''''''''''''''''' '''''''''''''''''''''].
- c. Please identify and justify any major changes between the RODEX4 kernel and the approved methodology described in BAW-10247PA, Revision 0, and approved supplements thereto. Please further describe whether AURORA-B test problems exist that verifies that the RODEX kernel in AURORA-B predicts behavior equivalent to the stand-alone code for transient conditions.
RAI-15
During an audit on May 16-18, 2017, AREVA stated that it seeks the NRC staffs review and approval of AURORA-B [''''' '''' ''''''''''''''''''' '''''''''''' ''''''''''''''''''' '''''''''''' '' '''''''''''''''''
''''''''''' ' '''''''' ''''''''''''''''''''''''' '''''''''''''' ' ''''''''']. In light of this voluntarily implemented change in S-RELAP5 code version, additional information is necessary to describe the changes in the new code version, as well as its impact on the validation and demonstration analyses in ANP-10332P:
- a. Please provide description, at a level of detail commensurate with a TR, of any changes to the AURORA-B LOCA EM resulting from the change in S-RELAP5 code version and provide justification for the acceptability of the changes.
- b. Please provide an updated version of the validation and assessment analyses demonstrating that the AURORA-B code systems validation and assessment results using the [''''''''''''''''''] version of S-RELAP5 are acceptable. Please confirm that the discussion and conclusions expressed in ANP-10332P regarding the validation and
assessment results remain accurate, or provide an updated discussion and conclusions.
- c. Please provide updated demonstration case (i.e., BWR plant analysis) results that illustrate how the AURORA-B code system with the ['''''''''''''''''' ''''''''''''' ''''''''''''''''''''
'''''''''''''' '''''''' '''''''''' ''' '''' '' ''''''''''' '''''''''' ''''' '''''''''''''''''''''''' '''''''''' ''''''''''''].
Please confirm that the discussion and conclusions expressed in ANP-10332P regarding the demonstration case results remain accurate, or provide an updated discussion and conclusions.
RAI-16
The AURORA-B LOCA EM chose to use the Groeneveld 2006 CHF look-up table (LUT) over other steady-state correlations deemed acceptable in Appendix K to 10 CFR Part 50. The following questions seek clarification of the implementation of the CHF LUT in the EM.
- a. Section 6.4.10 of ANP-10332P states that eight rod-bundle correction factors may be applied to the Groeneveld CHF LUT used in AURORA-B. These correction factors appear to contain fuel-design-specific aspects. To illustrate AREVAs use of these factors, please provide a table that identifies the values of these correction factors for the ATRIUM 10 fuel design.
- b. According to Section 6.4.10 of ANP-10332P, applying only the hydraulic diameter factor to the CHF LUT results in an underprediction of the critical power for the ATRIUM 10 fuel bundle. However, [' '''''''''''''''''''''''''' '' '''''''''''''' ''''''''''''''''''' '''''''''''''''''' ''
'''''''''''''''''''''''''''''''''''''''] Please further (1) explain quantitatively the impact of the other
['''''''''' ''''''''''''''''''''' ''''''''''''''''''''' '''''''''''''' ''''''''''''''''''''''''''' '''' ''''' '' ''
''''''''''''''''''''''' ''' ''''''' ''''' '' '' '''''''''''''' '''''' ''''''''' ' ''''''''''''''''''' '' ' ''''], and (2) provide justification that implementation of the method used for the AURORA-B LOCA EM would result in an overall conservative prediction.
- c. Section 6.4.10 of ANP-10332P states that ['''''''''' '' '''''''''''''''''''' '''''''' '''''''''
''''''''''''''''''''' ''''' '''''' '''''' '''''' '''''' ''''''''''']. How does the determination of the [''''''
'''''''''''''''' '''''''''' ''' ''''''''' '''''''''''''''''''' ''''''''''''''''] account conservatively for the uncertainty of the fuel-specific CHF/CPR correlations? Furthermore, which method does the EM use to determine the CHF value during transient and the value of the [''''''''''''''''
''' ''' ''''''''''''' '''' '''''']?
- d. The functional forms of the eight rod-bundle correction factors for the CHF LUT are summarized in ['''''''''''''' '''''''' '''''''''''''''''' ' '''''''''''''''''''''''''' '''''''''''''''''''''''''''
''''''' ''''''']. Explain the rationale for the selection of [''''''' '''''''''''''''''' ''''''' '''''''
'''' '''''''''' '''''''''''''''''''' ''''''''''''' '' ''''''''''''''' '''''' ' ''''''' '''''''''''''' '''].
RAI-17
ANP-10332P proposes that [''''''''''''''''''''' ''''' '''''''''''''''''''''''''' ''''' ''''''''''''''''''''''''''''' ''''
'''''''''' ''''''''''''' ''''''''''' ''''''''''''''''''']. Please clarify the following regarding this approach:
- a. Under what circumstances does ['' ''''''''''''''''''''' '''''' '''' ''' '''''''''''''''''''''''''''' '
' ''' '''''''''''' ''''''''''''' '''''''''' ''''''''''''''''' ''''''''''''''' '' '''''''' '''''''''''''''' ''''''''''''''''''''''''']
- b. AREVA explained in ANP-10332P that the ['''''''''' ''''''''''''''''' '''''''''' '''''''''''''''''''' '''''''''''''
'''''''']. However,
- i. ['''' '''''''' '' ''''''''''''''''' ''''' '''''''''''''''' ''' ''''''''' ''''''''''''''''''''' '' '''
''''''''''''' ' '''''''''''''''''' ''''' ''''''''''''''''''' ']
ii. ['''' '''''''''''''''''''''''' ' '' ''''''''''''''''' '''''''''''''''' '''''''''''''''' ''''''''''''' ''''''' ''
'''''''''''''''' '''' '''''''' '' ''''''''' '''''''''''''''''']
iii. The Opinion of the Commission on the 10 CFR 50.46 rulemaking, dated December 28, 1973, on Page 1116 appears to [''''''''''''' ''''''' '''''''''' ' ''''
''''''''''''''''''' ''''''''' ' '''''''''''''''''''' ''''''''''''''' '''''''''''''''''''''''']. In particular, the Opinion stated disagreement with a proposal that critical heat flux exceedances on the order of milliseconds may be neglected. In light of the Commissions Opinion, please justify that the proposed approach is compliant with Appendix K or revise it to be compliant.
- c. In light of the large, well-curated database associated with the Groeneveld 2006 CHF LUT and ['' '''''''''''''''''' ''''''''' ' '''''''''''''' ''''''''''' ''''' ''' '''''''''''''''''''''''' '''''' '''''''
''''''''''''''''' '''''''''''''''''''''''''' ''''''']. In doing so, please discuss the qualification data for the [''''''''' '''''''''''''''''''''] and justify that the model and its qualification database are applicable to the spectrum of BWR LOCA events, particularly around [''' '''''''''''''''
''''''''''''''' ''''''''' ''''''''''''''']. Please discuss in particular whether, prior to reaching
[''''''''''' '''''''''''''''''' '''''''' '''''''''''''''''''' ''''''''''''''''''''''' ' '''''''' ''' ''''''''''''''''''' '''''''''
''''' ''' ''''''' ''''']. Justification should be provided if the ['''''''' ''''''''''''''''''''''] is being applied under such conditions, since it is not clear that it is applicable.
RAI-18
Appendix K states that After CHF is first predicted at an axial fuel rod location during blowdown, the calculation shall not use nucleate boiling heat transfer correlations at that location subsequently during the blowdown even if the calculated local fluid and surface conditions would apparently justify the reestablishment of nucleate boiling. Heat transfer assumptions characteristic of return to nucleate boiling (rewetting) shall be permitted when justified by the calculated local fluid and surface conditions during the reflood portion of a LOCA.
and Transition boiling heat transfer shall not be reapplied for the remainder of the LOCA blowdown, even if the clad superheat returns below 300 °F, except for the reflood portion of the LOCA when justified by the calculated local fluid and surface conditions.
Although in both cases Appendix K explicitly speaks of implementing these heat transfer lockouts during the blowdown phase and releasing them during the reflood phase, [''''''''''''
''''''''' ''''''''''''''''''''''''''''' ' ''''''''''''''' ' ''' ''''''''''''' ' '' '''''' ''''''''']. Therefore, [''''''''''''''''
'''''''' ' ''''''''''''''''''' ''''''''' '''''''''''''''''''' ''' '''' '' ''''''''''''''''' '''''''''] is not clear and requires justification:
- a. Please provide a more detailed description regarding the [''''''''''''''' ''' '''''''' ''''
'''''''''''' '''''''''] as used in the AURORA-B LOCA EM. In addition, for one small- and one large-break demonstration case audited by the NRC staff, please identify the times in the calculation that correspond to the [''''''''''''' ''''''''''''''''' '''''''''' '''''''''''''''' ''
'''''''''''''''''''''' ''''''' ''''' '''''''''''' ''''''''''''''].
- d. Please describe the expected [''''''''''''' ' ''''''''''''''''''' ''' '''''' ''''''''''''' '''''''''''''''' ''
'''''''''''''''' ' '''''''''''''' '' ''''''''''''''''''' ''''''''''' ''''''''''''' '' '''''' '' '''''' '''''''''']
- c. Please either revise ANP-10332P to comply with the requirements of Appendix K or justify that the current approach is compliant with Appendix K.
RAI-19
ANP-10332P states that the Groeneveld-Stewart correlation is less conservative than the Appendix K criterion for minimum film boiling temperature (i.e., Tmin) below approximately 0.26 MPa (~ 38 pounds per square inch absolute (psia)). Please discuss the relevance of this observation relative to the pressure range associated with BWR LOCA scenarios for large and small breaks for Mark I, II, and III containment designs and justify that the Groeneveld-Stewart correlation is appropriate. Please explicitly address the observation that, ['''''''' ' ''''''''''''''''''
'' ''''''''''''''''''' ''''''''].
RAI-20
Regarding the information presented in Figure 6-20 of ANP-10332P:
- a. Please provide an additional, zoomed-in plot to supplement the information in Figure 6-20 that better resolves the ['''''''''''''''''''''''''''''''''''''''''' '''''''''''''''''''''''' '''''''''''''''''''''''''
'''''''''''''' '''' ''''''''''' ' ''''''''' ''''''''''''''' ''''''''' '''''''''''''''''''''''''''' ''''' ''''''] (this range is of significant interest for BWR LOCA events post-blowdown).
- b. Please explain the ['''''''' ' '' ''''''''''''''''''' ''''''''''''''''''' ' ''''''' '''''''''''''''' '''''''''''''''''
''''''''''''''''' ''''''''''''''''''''''' ''''''' ''''''''' ''''''''''' '''''''''''''''''''''''''''']
- c. Please further explain ['' '''''''''''''''''''''''''' ' '''''''' '''' '' '''''''''''''''''' '''''''''''''''''' ''
''''''''''''''''''''' ''''' '''''''''''''''''' ''''''''''''''''']. Which of these conditions is most applicable for the spectrum of BWR LOCA events, as predicted by the AURORA-B LOCA methodology? In responding, please reference one of the demonstration cases audited by the NRC staff, since, as noted above, it is not clear ['''' '''''''' ''''''''''''''''''''''''
''''''''''''''''''' '''''''' '' ''' '''''''' '' '' '''']
RAI-21
Please provide adequate basis that ['''''''''''''''''''''''''''''''' '''' ''''''''''''''''' '''''''''''' ''''''''''''''''''''''' '''' '
'''''''''''''''''''''''].
RAI-22
Regarding the CCFL testing in the mini-loop described in Section 5.4.8 of TR, please clarify how the testing was scaled geometrically so as to represent the actual plant condition. In particular, the flow area distribution along the upper tie plate surface is not uniform, and it is not clear how the scaling was done to ensure applicability to the full-size condition.
RAI-23
ANP-10332P states in Section 6.2.5 that The suitable calculation for gamma energy deposited in the fuel is AREVAs BWR fuel management reactor physics code used for reload licensing analysis. [ '''' '' '''''''''''''''''''''''''' '''''' ''''''''''' ''' '''''''' ''''' '''''''''''''''''' ''' ''''''''''''''
''''''''''' ]. Please either (1) confirm that the generic methodology in ANP-10332P will ['''
''''''''''''''''''''''' ' ''''''''''''''''''' '' '''''''''''''' ''''''''''''' '''''''''''''''''' ''''''''''''''''''''], including:
- a. Identification of the current BWR fuel management reactor physics code and the extent to which this code been reviewed by the NRC staff for ['''''''''''''''''' '''''''''''''' '''''''''''''
''''''''''''''''''''' '''''''' ''''''''''''''' ''''''''''''''''].
- b. Description of the [''''''''''' '''''''''' '''''''''''''''''' '''''''''' ''''' ''''''''''''''''' ' ' '''''''''''''
''''''''''''''''''''' '''''''''''].
- c. Discussion of the ['''''''''''''''' ' '' ''''''''''''' '''''''''''' ''''''''''''''''' '''''''''' '''''''''''''''''''''' ''''''''
'''''''' '''''''''' ''''''''''''''''''''].
RAI-24
Appendix K to 10 CFR Part 50 states that if the results indicate that the maximum clad temperature for the LOCA is to be found at an even lower value of the discharge coefficient than 0.6, then the lower range shall be extended until the maximum clad temperature has been achieved. Please provide the following information to justify the statement in ANP-10332P that
[''''''''''''''''' ''''''''''''''''''' '''''''''' '' '' ''' ' '''''''''''''''''' '''' '''''''''''''''''''' '''''''''''''''''''''''''']:
- a. Clarify why [ ''''''''''''''''''' '''''''''''''''''' '''''''' ''' ' '''''''''''''''''' ''''''''''''''''''' ' '''''' ' '''
'''''''''' ' '''''''''''''''''''''''''']?
- b. The TR states that [ '''''''''''''''' ''''''''''''''''''''' '' ' '''''''''''''''' '' ' '''''''''''''''''' '''''''''
'' ''''''''''' '' '''''''''''''''''' ''''''''''''''''''''' '' ' '''''''' ''''''''''' '''' '''''''''''''' '''''''].
RAI-25
ANP-10332P indicates that the Moody model ['''' '' ''''''''''' ''''''' ''''''''''''' ' ''' ''''''
''''' ''''''''''' '' ''''''''''''' '''''''''''' ''''''' ''' '''''' ' '''''''''''' '''''''''']
RAI-26
Please describe how ['''''''''''''' '''''] is modeled in the AURORA-B LOCA EM for the primary system safety/relief valves (SRVs), which may be opened in some LOCA scenarios at high pressure when the automatic depressurization system is activated. Please include a description of the [''''''''''''' '''''''''''''' '''''' ''' '''''''''''''''''''''''' '''''''''' '''' ' '''''' ''''' ' '''' ' '''''
''''''''''''''''''' ' '''''''' '''''' ''''''''''''''''''' ''''''''''''''''''' '''''''' ''''''' ''''''''' '''''''].
RAI-27
ANP-10332P does not define which [''''''' ''''''''''''''''' ''''''''''' '''''''' ' '''''''''''''''' '' '''''''''''''''''''''''
'''''''''' ''''''''''''''''''' ']. Therefore, please provide the following information:
- a. Identify the ['' '' '''''''''''''''''''' '''''''' '''''''''''''' ''''' ''''''''''''''''' '''''''''''''' '''''''''''''''''''
''''''''''''''''''''''' '''''''''' '''' ''''''''''''''''''''''' ''''''''''' '''] in conformance with Appendix K.
- b. Either (1) confirm that the ['' '' ' '''''' ''''''''''' ''''' '''''''''''''''''' '''''''''''''''''' '''''''''''''''
'''''''''''''' '''''''''''''''''''''' ''''''''''''''''''''''' ' ''''''''''' ''' '''''''''''''''''''''''''' ''''''''' '''] were used when performing each of the analyses included in ANP-10332P (e.g., those used for code assessment and validation, demonstration cases, etc.), (2) provide additional simulations with the [''''''''''''''' '' '''''' '''''''''' '''' '''''''''''''''''' ''''''''''''''' ''''
'''''''''''''''''], or (3) identify [''' '''''''''''' '''''''''''' '''' '''''''''''''''''' ''''''''''''''''' ''''' '''''''' ''
''''''''''''''''' '''''' '''''''''''' ''''' ''''''''''''''' '''''''''''''''' ' '' '''''''''''''''''].
- c. When performing [''''''''''''''''''''''''''] analyses in accordance with the methodology described in ANP-10332P, please explain ['''''' '' ''''''''''''''''' ''' ''''''' ''''''''''' '''''
''''''''''''''''' '''''''''''''''' ''''''''''''''''' '''''''''''''''''''''''' '''' ''''''''''''''''''''''''' ''''''''''''''] will be implemented and verified in a way that minimizes the potential for human error and unintended variation. For example, having a ['''''''''' '''''''''''' '''''''''''''''''''''''''' '''' ''''
''''''''''''''''''''''' '''''''''' ''''''''''''''''' '']
RAI-28
Chapter 15 of the SRP and Regulatory Guide 1.203 both specify that an analytical EM submitted for NRC review should be frozen (i.e., placed in a controlled, unchangeable state).
These guidance documents further indicate that the code assessment and validation process should be performed with the frozen version of the EM that has been submitted for review. The NRC staff likewise expects that the demonstration analyses submitted in the TR should be performed with this same frozen version to demonstrate expected performance of the EM under review. However, ['''''''''''''''''''''''' ' ''' '''''''' '''''''' ''''''''''''' '' '''''''''''''''''''''' '''''''''''''''' '''''''''''''
' '' ''''''''''''''' ' '''''''''''''''''''''''''' '''' '''''''''''''''''''''''''' ''' '''''''''''''''''''' ''''' ' ''''''''' '''''' ''''''''''''].
Therefore, please provide the following information:
- b. Identify the code version that AREVA has used to perform the assessment and validation simulations in the TR . Either (1) confirm it is the same as the frozen code version associated with the AURORA-B LOCA EM, (2) provide additional simulations with the appropriate frozen code version, or (3) provide justification that additional simulations with the frozen code version are not necessary.
- c. Identify the code version that AREVA has used to perform the demonstration case simulations in the TR. Either (1) confirm it is the same as the frozen code version associated with the AURORA-B LOCA EM, (2) provide additional simulations with the
appropriate frozen code version, or (3) provide justification that additional simulations with the frozen code version are not necessary.
RAI-29
ANP-10332P primarily focuses upon concerns associated with code development and validation. A number of relevant aspects of the broader EM are not treated. Therefore, please discuss the following aspects of the framework for applying the AURORA-B LOCA EM to plant-specific analysis and provide justification. For each item, specify whether plant-specific determinations must be made, or whether a generic basis exists to disposition the item in the present review.
- a. Which break locations on which systems must be considered in the LOCA analysis, and how are the analyzed breaks selected? ['''''''' ' ''''''''''''''' ''''' '''''''''''''''''''''''''''' '''''''' ''
'''''''''''''''''' '''''''' ''''''''''''' '''''''''''''''''''''' ''''''' ''''''''''''' ''''''''''''' '''''''''''''']
- b. What are the required extent and resolution of the break spectrum for selection of the limiting break and single failure combination? In responding, please provide adequate justification for (1) the resolution used for intermediate breaks [''''''''' '''' '
''''''''''''''''' ' '''' ''''''''''''''''''' ''''''''''''' '''''''''''''''''''''' '''''''''] and (2) the selection of the minimum analyzed break size in the small-break range ['''''''' '''''' ''''''''''' '
'''''''' ' ''''''''''''' ' '''''''' ''''''''''']
- c. For split breaks, [ ''''''''''''''''''''' ''''''''''''''''' '''''''''''' ''''''''' ''''''''''''''''' '''' '''''''''
''''''''''''''''''''''''' '''''''''''' ' ''''''''''''' '' '''''''''''''''''''' '''''''' ''''''''''''''']? In responding, please consider conditions during blowdown where the break flow is choked, as well as conditions later in the event after the break has unchoked.
- d. Should a split break occur on the recirculation discharge piping for the BWR/3-4 design, low-pressure coolant injection flow pumped into the broken recirculation discharge piping may have the potential to enter the reactor vessel. Please clarify if credit is taken for safety injection flow to the broken loop in the case of a split break. If credit is taken, then please describe the governing phenomena, the applicable modeling practices (including modeling of break azimuth) in AURORA-B, and the validation basis for the associated AURORA-B models. As applicable, please also clarify the impacts of loop-select logic (including the possibility for this logic to experience a single-failure and the minimum break size for which it is effective).
- e. Can a single simulation simultaneously achieve limiting conditions for peak cladding temperature, maximum local oxidation, and core-wide oxidation, or are separate analysis cases, potentially with different initial conditions, different break locations, and single failures, necessary to achieve the limiting results for each of the relevant criteria from
10 CFR 50.46? Please clarify in particular, how the limiting oxidation results ['''''' '
'''''''' ''''''''''''''' '''''''''''''''''''''''''].
- f. How is the most-limiting single failure for each analysis determined? Does the method recognize that the limiting single failure is generally scenario dependent?
- g. What key initial conditions will be specified in each analysis ['''''''' ''''''''''' ''''''''
''''''' ''''''''''''''''''' '''''' '''''' '''''''''' '''''''''' '''''' '''''''''''''''' ''''''''''''' ''''']? In each case, please identify whether nominal conditions will be used or whether a conservative assumption will be used, and provide a technical basis. If a single set of initial conditions is insufficient to ensure that limiting results are calculated for each of the relevant criteria from 10 CFR 50.46 (e.g., if multiple points on the power-flow map must be considered),
then please provide information for all relevant cases that would need to be simulated.
- h. Discuss assumptions regarding the availability of offsite power, the response of non-safety-related equipment, and operator actions.
- i. Please clarify whether ['''''''''' '''' '''''' ' '''''''''''''''' '''''' ''''''''' ''''''''''' '''''''''''''''
''''''' ''''''''''''' '''' '' ''''''''''''''' '''''' ''' ''''''''''''''' '' '''''''''''''''''''].
- j. In large-break LOCA scenarios, [''''''''' ''''''''''''''' ''''' '' ''''''''''''''''' ' '''' '''''''''''
'''''''''' ''''' '''' '''''''' ' ''''''''''''''''].
- k. How is the limiting [''''' '''''''''' ''''''''' '''''' '' '''' '' '''''''''''''''''''' ''''''''''''''''' ''''''''
'''''''' '''''''''''''''''''''''']? In particular, because of the potential for bottom-up and top-down quench fronts in the BWR design, [ ' '' ''''''''''''' ''''' '''''''''' '''''' '''''''''' '''''''''''
''''''''''''''' '''' ''''''''''''''' '' '''''''''' '''''''''' '''''' '''' ' ''''''''''''''''' ''''''''' ''''''''''''''''''''']
Therefore, please provide adequate justification for the adequacy of the existing method or commit to performing a plant-specific ['''''''''''''''''''' '''''''''''''' '' '' ''''''''''''' ''''''' ''''''''
'''''''''']. Please further ensure that the response considers the requirements for
['''''''''''''''' '''''''''''' '''''''''''' '''''' ''''''' '''''''''''''''''' ' ''''' ' ''''''' '''''''' ''''''''''''''''''' ''''
'''''''''''''''''' '''' ''''''''''''''''''''''' ' ''''''''' '''''''''''''''' ' '' '''''''''''''''' '''''''''''''''''''''''''''].
- l. Please discuss the modeling of the linear heat generation rate, decay heat, and stored energy for ['''''' '' '''' '''''''''''' '' '''''''''''''''''''''''' ''''''], and explain how AREVA has conservatively modeled these parameters in an overall sense for [''''' ''' '''''''' ''
'''''''' ''''''''].
RAI-30
In Section 3.3 of ANP-10332P, AREVA indicates ['''' '''''''' '' ''''''''''''' ''''''''' ''''' ' '''
''''''''''''' ''''''' ''''''''' '''''''''''' ''''''''' ''' '''''''' ' ''''''''''''' ''''''''''''''''''''' ''''''''''''''''']
RAI-31
In Section 3.3 of ANP-10332P, AREVA states [''''' ' '''''''''''''''' '''''' ' ''''''''''''''''''''' ''''''''' ''
''''''''' '''''''' ''''' ''''''''''''''''''''' '' ''''''''''' ''''''''''''''''''' '''''''''''''''''''''''' ' ''' '''''''''' ''''''''''''']
RAI-32
ANP-10332P did ['' '''''''''''' ''''''''''''''' '''''''''''''''''''''' ''' ''''''''''''''''''''''' '''' '''''''''''''''''''' '''''''''''''''''''''
'' ''''''' ''''''''''' '''' ''''''''''' ' ''' ''''''''''''' '''''''''''' '''''''''''' ''''''''']. Therefore, please address the following requests:
- a. Page 6-37 of ANP-10332P states that [''''''''''''''''''''''' ''''''''''' ''''''''''''' ''''''''' '' ''''''
'''''''''''' ''''''''''' '' '''''' ''''''''''''' ' ' ''''''''''''' '''''''''''''''']
- b. From a simulation perspective, [''' ''''''''' ' ''' ''''''''''''''''''' ''''''''''' '''''''''''''''''''''
''''''''' '''''' ''''''''''''''''''''''''' '''''''''''' '' ''''''''''''''' ''''''''''''''''''' '''''''''']. The basis for these predictions, as well as other similar examples in Tables 7-62 through 7-65, is not obvious, nor is it explained in ANP-10332P.
- i. Please provide an explanation for the ['''''''''''''' ''''''''''''''''''' '' ''''' '''''''''''' '
'' ''''''''''''''' '''''''''' ''''''''''''''''' '''''''''''].
ii. Please clarify and provide justification for AREVAs position regarding ['''''''''''''' ''
'''''''' ' '''''''''''' '' '''''' ' '''''''''''''''''''''''' '''''''''''''''''' '' ''']
- c. The [''''''''''''' ''''''''''''''''''''] proposed in ANP-10332P for plant analysis ['' '''''''''''''''
''''''''''''''''''''''''''''''' '''''''''''''''''' '''''''''''''' '' ''' ']. In light of the discussion above, please clarify whether sensitivity studies have been performed to demonstrate that significant changes in the prediction of (1) [''''''''''''' ''''' ''''''''''''''] and (2) the figures of merit from 10 CFR 50.46 for the full-size plant application would not occur if
- i. ['''''''''''''' ''''''''' ''''''''' '''''' '''''' ''''''''''''''''''''''' '' ''''''' '''''' '' ''''''''''''''''''
''''''''''' '''''''''''' ''''''''' '''''''''''' ''''''''''''''''']
ii. [' '''''''''''''''''''' '' ''''' ''''''''''' ''''''''''''''''''' ''''''' '''''''''''''''']
- d. Please clarify whether AREVA has performed ['''''''' ''''''''''''''' '''''''''''''''' '''''''''''''''''
''''''''''''' ' ' ''''''''''''''''''''''''''''' '''''''']
- e. Discuss assumptions for [''''' ''''''''' ''''''''''''''''''' ''''' '''''''''''''''' '''''''' '' '''''''''''''''' ''''''
''''''''''''' '' '''''''''''''''' '''''''']. Have sensitivity studies been performed to show the effects of variations in these factors and their impact on whether [ ''' '''''''''''''''' ''''''''
' ''''' ''''' ''''''''''''''''''' '''''''''' ''''''''']?
- f. Upper plenum conditions ['''''' '''''''''''''''' '''''''' ''''''''''''''''''''''' '''''''' ''''''''''''''''''' '''' '''''
''''''''' ''' '''''''''' ''''''''''''''''''' '''''''''' '''''''''''''''''' ''''''''''''''''''''''']
- i. Please discuss how inaccuracy in predicting ['''''''''''''''''''' ''''' '''' '''''''''
''''''''''''''''''' ''''''].
ii. Please discuss how inaccuracy in predicting ['''''''''''''''''''''' ' '' '''''''' ''''''''''''''''
''''''''''''''''''''' '''' '''''''''''''''' '''''''' '''''''''''' '''''''''''''''''''' '''''''''''''''''''].
iii. Please discuss the basis for limiting ['''''''''''''''''''''''' ' '''' ''''' '' ''''''''''''''''
'''''''''''].
- g. Discuss the intent and significance of [''' ''''''''''''''''''' '''' ''''''''''''' ' ''''' ''' ''''''
''''''''''''''''''''''''''' ''''''''''''''' ''' ''''''''''''' '' '''''''''''''' ''''' ''''''''''''''''' ' ''''''' ''''''].
- i. Which of the ['''''''''''''''''' ''''''''''' '' '''''''''''''''''''''''''''' ''' '''''''''' ''''' ''''''''''
'''' ''''''''''''''']?
ii. Provide justification if [''''''' ' ''' '''''''''''''''''' ''' '''''''''''''' ''''''' '''' ''''''''''''
''''''''''' '''''' ''''''''' ''''''' ].
iii. ANP-10332P states that it is anticipated that only ['''' ''' '''''''''''''' ' ''''''''''''
''''''''''''''''''' ''''''''''']
- h. Please identify whether any of the demonstration cases ['''''''''''''' ' '' ''''''''''''''' '
''''''''' ''''''''''''''' ''''''''''''''' ''''''''''''''''''''''''''' '''''''''''''''''' ''''''''''''' ''''''''''''' '''' ''''''''''''''''].
- i. Please confirm that the [''''''''''''''''''' ' ''''' '''''''' '''' ''' '''''''''''''''''' ''''' ''''' ''''''''''''
''' '''''''''''' '' ' '''''''' ' '' '''''''''''''''''''''''''''''''' ''''''''' '''' '''''''' ''''''''''''''''''''''''].
RAI-33
Bypass leakage flowpaths are important in determining BWR LOCA behavior. Please provide the following information regarding bypass leakage paths:
- a. Which specific bypass leakage paths (e.g., between bypass region, fuel bundle, lower plenum, guide tubes) are explicitly modeled in the AURORA-B LOCA EM?
- b. What are the characteristics of these flowpaths? Which are the most significant (i.e., in terms of flow area or flow rate under nominal design conditions)? Please further clarify the method used to determine the characteristics for all leakage paths (e.g., measurements, calculations), especially for the fit-up gaps, which are more difficult to determine analytically in an accurate manner.
- c. Clarify language on Page 6-37 of ANP-10332P. Reference is made to four leakage paths, [''' '''''' ''''''''' '''''''''' ' ' ''''''']:
There are four leakage paths for which reverse flow (also called backflow) is important in the LOCA evaluation. These leakage paths are included as junctions in the LOCA modeling of the reactor. These leakage paths are between the bypass and core regions, the bypass and lower plenum, and the control rod guide tubes and lower plenum.
- d. Discuss whether any significant bypass leakage paths are neglected in the AURORA-B LOCA EM, and, as applicable, the resulting impacts on the output of the EM.
- e. Please show the bypass leakage paths discussed above on an illustrative diagram (e.g., Figure 6-13 of Lahey and Moody, The Thermal-Hydraulics of a Boiling Water Nuclear Reactor, Second Edition).
- f. Describe how hot wall effects are modeled, and provide a basis for the models used.
RAI-34
['''' '''''''''' '''''''''''' ''''''''''' ''''''''''], could the reactor pressure be temporarily reduced below the containment pressure (e.g., due to the spraying of cold water in the upper plenum), [such
'''''' ''''''''''''''''''''''''' ''''''' ' '''''''''''''''''' ''''''''''''''''''''''''''''' ''''''' ''''''''''''']? In addressing this question, please provide the following information:
- a. Describe the modeling of the [''''''''' '''''''''''''''''''''' ' '''''''''''''''''''''''' '''' '''''''''''''''' ' '
''' '''''''''''''' '''''].
- b. If AREVA concludes that [''''''''''''''''''''''''''''''''''' '''' '''''''''''''' '''''''' ''''''''' ''' '''''''''' '
'''''''''''''''' '''''''''' '''''''' ''''''''''''''''''''''''' ''''''''''''''''''''''].
- c. If AREVA concludes that [''''''''''''''''''''''''''''''' ''''' ''''''''''''' '''''''' '' ''''''' '' '''''''''''' '
'' '''''''''' ''''''''''' ''''''''''''' ''''''''].
RAI-35
Section 6.3.7 of ANP-10332P provides nodalization diagrams ['' '' ''''''''''''' '''''''''' '''''
''''''''''''''' '''''''''''''''''''' ' '' '''''''''']. If additional systems will be explicitly simulated in the AURORA-B EM, then please provide applicable nodalization diagrams and justify that the credit taken for these systems is appropriate.
RAI-36
Heat structure modeling for the recirculation system [' '' '''''''''''''''' ''''''''' ''''
''''''''' '''''''''''' '' '''''''''''''''''''''''' '''''''''''''''' ''''''''' ''''] is accurate for the recirculation system and other systems such as the feedwater system.
RAI-37
Page 6-29 of ANP-10332P states that the vessel nodalization scheme for AURORA-B is similar to the 3-region TRAC model used in the U.S. NRC sponsored SSTF assessment of Reference 64 (J.A. Findlay, "BWR Refill-Reflood Program Task 4.4 - CCFL / Refill System Effects Tests (30° Sector), Evaluation of Parallel Channel Phenomena," NUREG/CR-2566, GEAP-22044, EPRI NP-2373, Nov. 1982.) However, the NRC staff could not find the cited TRAC model in Reference 64. Please clarify.
RAI-38
In the AURORA-B EM, AREVA has [''''''''''''''' '''''''''''''''''' ''' '' '''''''''''''''''' ''''' '''''' ''
'''''''' '''''''''''''' '''''''''''''''''''''''']
RAI-39
Please clarify AREVAs modeling practices for the fuel bundle represented by the hot channel in Section 6.3.8 and Figure 6-10 of ANP-10332P.
- a. In the [''''''''''''''' ''''' '''''''' '''''''' ''''''''''''''''' '' ''''''' '''''''' ''' ''''' '' ''''''
''''''' ''''']?
- b. Please provide a more-detailed diagram for an [''''''''''' ''' ''''''''' '''''''' '''''''''''''' '''
''' ''''''''''''' '''''''''''''' '''''''' '''' '''''''' '''''''''''''''].
- c. If AREVAs modeling practices would allow the ['' '' ''''''' ' '''''' ''''''''''
'''''''' ''''''''''''''''' '''''' '''''''''''' ''''''''''''' ''''''''''''''''''''''''].
RAI-40
Please justify the alternative to the [''' '''''''''''''' '''''''''' '''''''''''''''''''' ' ''''''''''' '''''''''' ''''''''''''''
''''''''''''''' '''''''''' '''''''''' ' ''''''' ''''''''' ''' ''''''''''''' ''''''''''''']. It is not clear to the NRC staff whether sufficient benchmarking and validation has been performed for this case. Please provide adequate justification that the alternative model has been conservatively compared to an adequate quantity of experimental data, or commit to providing such justification for plant-specific applications.
RAI-41
Section I.C.1.d of Appendix K requires that the nodalization in the vicinity of and including the broken or split sections of pipe and the points of ECCS injection shall be chosen to permit a reliable analysis of the thermodynamic history in these regions during blowdown.
Section 6.2.13 of ANP-10332P [''''' '''''''''''''''''' '' ''''''''''''''''' ''' '''''''''''''''''' '''''''''''''''' '''''
'' ''''''''''''''''' ''''''''''''''''' ' ''''''''''''' '' '''''''''''''''''''''''''''] address the specific requirement of I.C.1.d of Appendix K. Provide evidence demonstrating compliance of the EM with this Appendix K requirement.
RAI-42
Describe the process for determining [''''''''''''''''''' '''''''''''''''' '''''''''' ''''' ''''''''''' '''''''''''''' '''
'''''''''''''' '''''''''''''''''''''''' ''''''''''''''''' '''''''''''''''''']
RAI-43
Discuss the process and criteria for the determination of [''''''''''''''''''''' ''''''''''''''''''''''''''' '''''''
''''''''''''''''' ''' '''' '''''''''''''' ''''''' ''''''''''']
RAI-44
ANP-10332P states on Page 1-3 that the AURORA-B LOCA EM will use a point kinetics model with input or modeling parameters based on an appropriate core simulator code; for example, MICROBURN-B2.
- a. How does AREVA determine whether a core simulator is appropriate for use with the AURORA-B LOCA EM, and that the point kinetics inputs will be conservative? Is prior NRC approval of the core simulator code required?
- b. Please describe the specific inputs from MICROBURN-B2 to the AURORA-B LOCA EM or reference where they have been described.
- c. ANP-10332P states that inputs from XCOBRA may be used for determining steady-state flow distributions, in lieu of MICROBURN-B2. [''''''''''' '''''''' '' ''''' ''''''''''''''''' ''
''''''''''''''''''''']. In the case that XCOBRA is used, how are the point kinetics inputs to AURORA-B determined?
RAI-45
It is noted in Section 6.2.3 of ANP-10332P that AREVA will use [' ''''''''''''''''''' ''''''''' ''''' ''' '
'''''''''''' ''' '''''''''''''''''''']
RAI-46
Please describe the process of performing calculations [' '''''''''''''' '''''''' ''''' ' '' '''''
''''' ' ''''''' ''''''''''' '''''''''' '''''' '''''''''''''''''''''''''' '''''''].
RAI-47
After a PIRT has been generated, the EM development and assessment process calls for a validation matrix that lists separate effects tests (SETs) and integral effect tests (IETs) for validating each [''''''''''''''''''''''' ''''' ''''''''''''''''''''''''''''''''''' '''''''''''''''''''''''' ''''' ''''''' ''''''''' ''''''''''
'''''''' ''''''''''''''' ''''' ' ''''''' ''''''''' ''''''' '''''''''''''''' ''''' ''''''''''''''''''''' '''''''''''''''''''''' '''''''' ''''''''''''].
The validation descriptions, while listing the phenomena that are considered by AREVA to be validated by each individual test/facility, do not provide any evidence or discussion of how the validation [ '' '''''''''''''''''''''' ''''' ''''''''''''''''''''''''''''''''' ''''''''''''''''''''' ''''''''''''''''''' ' '''''' ''''' ''''
'''''''''''''''''''']. Therefore, additional information is needed to complete the validation description and conclusions for ['''''''''''''''''''''''' ''''' '''''''''''''''''''''''''''''''' ''''''''''''''''''''''' '''' ''''''''''''''' ''''' ''''
''''''''''''''''' ''''''''''' '''''''''].
RAI-48
A significant proportion of the tests and test facilities ['''''''''''''''''' '' '''''''''''''''''''' ''''''''''' ''''
''''''''''''''' '' '''''''''''''''''''''''' '''''''''' ''''']
RAI-49
A number of the models incorporated into the AURORA-B LOCA EM are required or acceptable features, as defined in Appendix K. ['''''''''''''''' '''''' ''''''''''' ''''''''''''' ''' '''''''''''''' ''''''''''''''
''''''''''' ''''' '''''''' '''''''''''' ''''''''''''''''''' ' ' '''''''''''''''''''''' ''''' ''' ''''''''''''''']. Appendix K states that, to the extent practicable, predictions of the EM, or portions thereof, shall be compared with applicable experimental information.
- a. Please explain how the assessment and validation performed for the AURORA-B LOCA EM is compliant with Appendix K to 10 CFR Part 50, which requires (under Part I) a comparison with experimental data for certain phenomena and further stipulates (under Part II) that, to the extent practicable, predictions of the EM, or portions thereof, shall be compared with applicable experimental information.
- b. In making valid comparisons against experimental data, consideration of experimental uncertainty and scaling may be important in assessing conclusions regarding the applicability of the tests and the level of agreement between the code and the data. In this regard, the brief summary discussion in Section 5.6 of TR is not sufficiently clear.
Please explain in more detail how experimental uncertainty is handled ['' ''''''''''' '''''
'' '' '''''''''''''''' ''''''''''''''''''''' '''''''''''''''' '' ''''''''''' ''''''''''''''' '] and provide examples.
RAI-50
[''''''''''' '''''''''''' ''''''''''' ''''' ''''''''''''''''''''''''''''] during the refill phase are important phenomena that [''''' ''''' '' '''''''''''''''''''''''''' ''' ''''' ''''''''''' '''''']. The introduction of cold liquid from the ECCS (particularly for BWRs where LPCI injects into the recirculation discharge line) into a
['''''''' ''''''''''''' '''''' ''''' '''''''' ''''''''''''''''''' '''''''''''''' '' '''''''''''' '''''''''''''' '''''''''''''''''''''''''''''' '''''
'''''''''''''''''''''''''' '''''''''''''''''''''''' '''''''''''''''''' ''''''''' '''''''''''' ''''''''''''''''''''''] Therefore, please either provide a specific comparison of the AURORA-B models prediction of these phenomena in the
[''''''' ''''''''''''''], or provide more detailed justification that the existing integral effects comparisons demonstrate an acceptably accurate prediction.
RAI-51
The NRC staffs audit review of the ['''''''' ''''''''''''''''''''''' '''''''''''''''''' '''' '''''''''''''''''''''' ''''''''' '
'' '''''''''''''''' '''''''''''''''''' '' ''' '''''''''''''''' '''''''''''' '' '' ''''''''''''''' ''''''''''''''''''''''], as well as (2) AREVAs rationale for implementing this change, are not clear. Please provide this additional information.
RAI-52
Discuss the practice of [''''''''''' '''''''''''''''''' ''''''''''''''''''' ' '''''''''''''''' ''''''''''''''''''''''''''''''''''' '''''''''''
'''''''''''''''' ''''''''''''''''''''], and further clarify the impact that this practice has on gauging the overall assessment of EM accuracy.
RAI-53
Please address the AURORA-B ['''''''''''''''''''''''''''''] prediction of FIST Test 6SB2C in Section 7.7.3.2 of ANP-10332P, and [''''''''' '''' '' '''''''''''''''''''''''''''''''''' '' '''''''''''''''''''' ''''''
''''''''''' '''''''''''''''''''']. The NRC staff made several observations concerning the AURORA-B
['''''''''''''''''''''''''''''''] prediction of this test:
- The predicted heatup rate appeared to be approximately ['''''''''''''''''''''''''''''' ''' ''''''''''''''''''''
' '''' '''''].
- The predicted heatup time appeared to be approximately ['''''''''''''''''''''''''' ''''' ''''''''''''''''''''
' '''' ''''].
- The predicted bundle mass is ['''''''''''''''''''''''' '''''''''' ''''''' '''''''''''''''''''' ' '' ''''' '''''''' ''
'''''''''' ''''''''''' '' '''' ''''''''''' ''''''' '].
- The experimental data showed [ '''''''''''''''''''' ''''''''''''''''' '' '''''''''' '''' ''''' ''''''''
'''''''''''''' ''''' '''''''''''''''' ' '''''' '''''' ''''''''''''''''''']
Although Section 7.9.2.2 of ANP-10332P contains an [''''''''''''''''''' '''''''''''''''''' '' ''''''''''''''
''''''''''''''''''''''''''''''''' ''''''''''''''''' '''''' ''''' ''''''''''' ''''''''''''' '' '''''''''''''' '''''''''''''''''' '' ]
RAI-54
Results for split breaks have been calculated in ANP-10332P up to a size [ '''' ''
''''''''''''''' ''''' '''' ]. Please explain the differences in behavior and clarify that the modeling of critical flow in each case is being performed in an acceptable manner.
RAI-55
Please clarify why [' ''''''''''''''''' ''''''''''' ''' '''''''''''''''''''' ' ''''''' '''''''' ''' ''''''''''''''''''''''''''''''
'''' ''''''' ' ''' '''''''''' '''''''''''''''''''' '''''''' ''''''''''''' '''' '''''''' '' ''''''''''' ' ''''''' ''''''''']
RAI-56
Demonstration cases for the BWR/6 ECCS configuration with a [''''''''''''''''''''''' ''''''''' ''''''''''
''''' ''''''''''' ' ''''''''''''''''']
RAI-57
On Page 7-340, ANP-10332P states that the ['''''''''''''''' '''''''''''''''''''''''''''''''''' ''' ''''''''''''''''''
''''''''''''''''''''''']
RAI-58
For limiting small-break and large-break demonstration cases, please provide a calculation to illustrate the impact of the conservatism imposed by the Appendix K EM by [''''''''''''' ''''''''''''''''''''
''''''''''''''''''''''' ''''''''''''''''' '''''''''']
RAI-59
Please explain the [''''''''''''''''''''] behavior observed during the audit in the ['''''''' ''''''''''''''''' '
''''''''''''''''''''''''''' ''''' ''''''''' ''''''''''''' '''''''' '''''''''']
RAI-60
The NRC staff audited S-RELAP5 output for the case [''''''''' ' ''''''' ''''' ''''''''''''''''''''''''''''
' ''''''''''''''' ''''''''''''''' ' ' ''''''''''''''''' '''''''''''' '' '''''''''''''''''''''''' '''']
RAI-61
Table 7-54 of ANP-10332P reports a value of ['''''''' ' ' ''' ''''' ' ''' ''''''''''''''' '''''' '''''
''''''''''''' ''''''' ''''''''' ''''' '' ''''''''''' '' '''''' '''''''''''''''''''''''''''' '''''''' ''''']
- a. Please clarify whether the results [''''''''''''''''' ' '''''''' ''''' ' ''' '' '''' ''''''''''''' ''''
'''''''''' ''' '''''''''''''' ''''''''''''''''''''''' '''''''''''''''''' '' '''''' '''''].
- b. Please describe how AREVA determines ['' ''''''''''' '''''''''' ''' ''''''' '''' '''''''
'''''''''''''''''''''''''' ''''''' '' ''''''''''''''']
1 According to AREVAs nodalization of the reactor core, two heat structure nodes representing a fuel rod are connected to a single hydraulic volume; this has resulted in each pair of axial heat structure nodes discussed together (e.g., 27 and 28) having essentially identical temperatures in this case.
RAI-62
Please describe how detailed component [''''''''''''''' ''''''''''''''''''''' '' ''' '''''''''''''''''''''' '''''''''' '''
''''''' ''''''''''' '' '''''' ''''''']
RAI-63
The AURORA-B code system is used in a [''''''''''' ''''''''''''' '''''''''''''''' ''''''''''''''''''''''''']. When the computer codes constituting AURORA-B (i.e., S-RELAP5, RODEX4, MB2-K) are further taken into account, the [' ''''''''''''''' '''''''''''''''''''''''''' ' ''''''''' '''' '''''''''''''''' '' ''''''''''
'''''''''''''''' ''''''''''''''''''' '''''' '''''''], it is possible that changes to AURORA-B or its subsidiary codes in support of ['''' ''''''''''''''' ''''''''''''''''''''''''''' '''''''' ''''''' ''''''''''''''''''''''''' ''''''''''''' ''''''''''' ''
'''''' '''''''''''''' '''''''''''''''''''''''''''''''''].
- a. How does AREVAs quality assurance program for AURORA-B and its constituent codes provide reasonable assurance that adverse impacts from changes in [''''' '''''''''''''''
''''''' ''''''''''''''''''' '''''''''''''''' ''''''''''''''' ' ''''''''''' ''''''''' ''' ''''' '' '''''''' ''''''']
- b. Have criteria been established to confirm that, when there is no impact expected from a change on [''' '''''''''''''''' '''''''''''''' '' '''''' ''''''''''''''' '''''''''''''''' ''''''' ' ''''''''''' '
''''''''''''''''' '''''''''' ' '''''''' '''''''''''''''' '''''''''''''']?
- c. Describe how quality assurance is performed on the [''''''''''''''''''''' ''''''''''''''''''
'''''''''''''''''''''''''] calculations to ensure that errors are not introduced, and that if errors are introduced, they can be identified and corrected.
- d. What is the full suite of validation problems that must be reanalyzed when updates are made to the AURORA-B code system? Does the validation suite contain suitable analyses for [' '''''''''''''''''''''''' '''' '''''''''''''''''''''' ''''' '''''' '' ''''''''''' ' ''' '''''''''''''''''''''
''''''''''''''''''''']?
RAI-64
According to Chapter 15.0.2 of the SRP, required input settings should be hardwired into the input processor so that the code stops with an error message when the required input is not provided or the input is not within an acceptable range, or administrative controls should be established to accomplish the same purpose. Further guidance is provided therein that all models should be assessed over the entire range of conditions encountered in the event scenario.
If required input is missing or in an unacceptable range, is the code automatically halted, or have administrative controls been established which serve the same purpose?
- b. If, during code execution, parameters passed to a given model or correlation are outside of its qualified and validated range of applicability, are error messages generated by the code? Is code execution halted, or does the code continue to execute, producing potentially non-physical or otherwise unacceptable results?
RAI-65
The use of revised analysis methods in lieu of those described in an approved TR is viewed by the NRC staff as a change to an EM that may, in general, require additional NRC staff review to ensure acceptability. For example, revised analysis methods may affect validation and assessment comparisons, code stability, and the results of demonstration analyses. In its present review of ANP-10332P, the NRC staff does not intend to authorize such changes absent future specific reviews. Therefore, please provide adequate justification for any conditions under which AREVA believes it has the authority to revise the AURORA-B LOCA EM, as described in ANP-10332P [''''''' '''''''''''''''''' ''''''''''''''''' ''''''''''''''''''''''''' ''''''], and continue to apply the revised EM as a generically approved method.