BSEP 18-0027, ANP-3655NP, Revision 0, Brunswick Mellla+ CRDA Assessment with Draft Criteria.

ANP-3655NP, Revision 0, Brunswick Mellla+ CRDA Assessment with Draft Criteria.

ML18075A331
Person / Time
Site:	Brunswick
Issue date:	02/28/2018
From:	Duke Energy Progress, Framatome
To:	Office of Nuclear Reactor Regulation
References
BSEP 18-0027, CAC MF8864, CAC MF8865 ANP-3655NP, Rev 0
Download: ML18075A331 (36)

Text

BSEP 18-0027 Enclosure 2 Framatome Report ANP-3655NP, Revision 0, Brunswick MELLLA+ CRDA Assessment with Draft Criteria (Non-Proprietary)

For Information Only 0414-12-F04 (Rev. 002, 01/15/2018) framatome ANP-3655NP Brunswick MELLLA+ CRDA Revision 0 Assessment with Draft Criteria February 2018 Framatome Inc.

(c) 2018 Framatome Inc.

For Information Only ANP-3655NP Revision 0 Copyright © 2018 Framatome Inc.

All Rights Reserved

For Information Only Framatome Inc. ANP-3655NP Revision 0 Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pae i Nature of Changes Section(s)

Item or Page(s) Description and Justification 1 All Initial Issue

For Information Only Framatome Inc. ANP-3655NP Revision 0 Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa e ii Contents Page

1.0 INTRODUCTION

............................................................................................... 1-1 2.0 DRAFT FUEL CRITERIA FOR REACTIVITY INITIATED ACCIDENT ........................................................................................................ 2-1 2.1 Regulatory Acceptance Criteria .............................................................. 2-2 2.1.1 Current Licensing Basis Criteria ................................................... 2-2 2.1.2 Draft NRC Criteria ........................................................................ 2-2 2.1.3 System Pressure and CPR .......................................................... 2-7 2.2 Core Coolability ...................................................................................... 2-8 2.3 CRDA Fuel Rod Failure Evaluation ...................................................... 2-11 2.3.1 PCMI Cladding Failure Criteria ................................................... 2-11 2.3.2 High Temperature Failure Threshold ......................................... 2-15 2.3.3 Release Fraction Scaling ........................................................... 2-17 2.4 Rod Failure Assessment.. ..................................................................... 2-23 2.5 Summary of Inherent Conservatisms .................................................... 2-25 2.6 Conclusion ............................................................................................ 2-26

3.0 REFERENCES

.................................................................................................. 3-1 This document contains a total of 35 pages.

For Information Only Framatome Inc. ANP-3655NP Revision 0 Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa eiii List of Tables Table 2-1 Summary of CRDA Results with Current Methodology ............................... 2-2 Table 2-2 Summary of Draft RIA Acceptance Criteria ................................................. 2-3 Table 2-3 Summary of Pressure and CPR criteria for CRDA Evaluation .................... 2-7 Table 2-4 Summary of Sample Plant CRDA Results with XN-NF-80-19 Methodology ............................................................................................ 2-12 Table 2-5 Highest Dropped Rod Worth Comparison ................................................. 2-12 Table 2-6 Total Deposited Enthalpy for Peak and Average Rod ............................... 2-15 Table 2-7 Actual TFGR Fraction versus [ ] Basis .................... 2-19 Table 2-8 Enthalpy and Exposure Dependent RFI Factors ....................................... 2-23 Table 2-9 Revised Rod Failure Count ....................................................................... 2-23 Table 2-10 Enthalpy and Exposure Dependent Total Release Fractions .................. 2-24

. Table 2-11 BSEP CRDA Radiological Consequences .............................................. 2-24

For lnforn1ation Only Framatome Inc. ANP-3655NP Revision 0 Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa eiv List of Figures Figure 2-1 PCMI Failure Threshold for SRA Cladding Low Temperature .................... 2-4 Figure 2-2 PCMI Failure Threshold for SRA Cladding High Temperature ... ;............... 2-5 Figure 2-3 High Temperature Cladding Failure Threshold .......................................... 2-6 Figure 2-4 Maximum Radial Prompt Average Enthalpy versus Rod Exposure ........... 2-9 Figure 2-5 Radial and Exposure Dependence of the Pellet Temperature Distribution .............................................................................................. 2-10 Figure 2-6 Prompt Enthalpy Rise versus Cladding Hydrogen Content with AURORA-8 Methodology ........................................................................ 2-14 Figure 2-7 Total Enthalpy versus High Temperature Failure Threshold (SRP4.2 AppB) ........................................................................................ 2-16 Figure 2-8 Total Enthalpy versus High Temperature Failure Threshold (DG-1327) ............................................................................................... 2-16 Figure 2-9 Axial Enthalpy Profile for Eight Representative Rod Drops ...................... 2-20 Figure 2-10 Nodal Transient Fission Gas Release Fractions .................................... 2-20

For Information Only Framatome Inc. ANP-3655NP Revision 0 Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa ev Nomenclature Acronym Definition

~H deposited enthalpy AST alternative source* term BOC beginning of cycle BSEP Brunswick Steam Electric Plant BWR boiling water reactor cal/g calories per gram CRDA control rod drop accident CWSR cold work stress relieved EOC end-of-cycle FGR fission gas release GWd/MTU Giga-Watt days per metric ton of uranium HEX excess clad hydrogen LAR license amendment request MELLLA+ maximum extended load line limit analysis plus MPa Mega-Pascal MWt Mega-Watts thermal NRC Nuclear Regulatory Commission PCMI pellet clad mechanical interaction PHEX peak hot excess ppm parts per million RAI request for additional information RFI rod failure increase RG regulatory guide RIA reactivity initiated accident RPF radial peaking factor SRA stress relieved and annealed (aka CWSR)

SRP standard review plan SSRF steady state release fraction TFGR transient fission gas release TOTR total release fraction (SSRF + TFGR)

UFSAR Updated Final Safety Analysis Report wppm parts per million weight percent

For Information Only Framatome Inc. ANP-3655NP Revision 0 Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa e 1-1

1.0 INTRODUCTION

This report has been prepared in response to NRC RAI SNPB-RAl-2 for the Brunswick license amendment request (LAR) maximum extended load line limit analysis plus (MELLLA+). The Brunswick MELLLA+ LAR requests an extension in the minimum core flow to 85% of rated from the current power flow map at rated conditions, currently licensed at 2923 MWt.

The issue being addressed in this report is draft NRC criteria for the BWR Control Rod Drop Accident. SRP4.2 Appendix B (Reference 1) provided interim criteria for new plants in 2007.

New draft criteria are provided in Draft Regulatory Guide DG-1327(Reference 3). This item is not part of the current licensing basis for BSEP. However, since the issue represents potential changes fo regulatory guidance, the NRC staff Requested Additional Information with respect to the potential impact of the draft criteria for the CRDA. At the time of the RAI, the revised criteria is not finalized nor has the NRC approved a Framatome method to evaluate the CRDA with the revised criteria.

The approach taken in responding to the RAI is to utilize a combination of approved methodologies as well as components of methods that are not yet part of the Framatome NRC approved methodologies.

The content of this report is a response to NRC SNPB-RAl-2 with respect to the potential impact of criteria similar to that provided in SRP4.2 and given in DG-1327. This assessment does not

~ ~ ., ~

support or propose any changes to the Brunswick plant CRDA licensing basis.

The RAI being answered is not specific to MELLLA+ but this response demonstrates that the new draft criteria can be met for the CRDA analysis for BSEP Units 1 and 2 if the criteria* were to be issued.

• It is anticipated that minor changes will occur in the criteria in response to public comment on DG-1327. No significant changes are anticipated that would alter the conclusion of this response.

For Information Only Framatome Inc. ANP-3655NP Revision 0 Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa e 2-1 2.0 DRAFT FUEL CRITERIA FOR REACTIVITY INITIATED ACCIDENT Reactivity Initiated Accidents (RIAs) are postulated accidents involving the sudden and rapid insertion of positive reactivity. For Boiling Water Reactors (BWR), the limiting RIA scenario is the Control Rod Drop Accident (CRDA). In support of the BSEP MELLLA+ LAR, evaluations of the BWR CRDA have been performed to address the current BSEP licensing basis using Framatome NRC approved methodology, as summarized in Section 2.1.1.

Draft guidance (Reference 3) for the RIA was published in November, 2016. The draft guidance addressed in this document is described in Section 2.1.2 and the evaluations are subdivided into two primary areas: 1) Fuel Melt, and 2) Fuel Failures.

The potential for cladding failure from fuel melt in the startup range is precluded in this evaluation by demonstrating that the incipient fuel melt temperature is not reached. The evaluation for fuel melt is addressed in Section 2.2 of this report, including impact on core coolability criterion 1 and 2.

Fuel failure assessment against the draft acceptance criteria is the subject of Section 2.3. The fuel failure subsections address various evaluations needed to support the overall fuel failure assessment as summarized below:

• Section 2.3.1: PCMI Cladding Failure Criteria - Addresses failures due to pellet clad mechanical interaction.

• Section 2.3.2: High Temperature Failure Threshold - Addresses potential for high temperature failures, including impact of internal rod pressure.

• Section 2.3.3: Release Fraction Scaling - Addresses the impact of including the transient fission gas release into the isotopic release fractions. This can impact the existing dose assessment. A method of adjusting the number of calculated rod failures is provided to compensate and maintain the current dose assessment basis.

• Section 2.4: Rod Failure Assessment - Combines the results of the previous subsections into a total number of fuel failures using the draft criteria.

This evaluation utilizes a combination of methodologies and analyses to comparatively address the impact of the draft regulatory acceptance criteria for CRDA for BSEP. In addition, significant conservatisms have been included as summarized in Section 2.5 of this report.

The draft criteria differ from that of SRP4.2 Appendix B. In the tabulation of results, the failure criteria of both SRP4.2 and DG-1327 are included.

For information Only Framatome Inc. ANP-3655NP Revision 0 Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa e 2-2 2.1 Regulatory Acceptance Criteria 2.1.1 Current Licensing Basis Criteria The current Regulatory Guide (RG) 1.77 RIA criterion is that the peak enthalpy must remain below a value of 280 cal/g. As described in Section 15.4.6 of the Updated Final Safety Analysis Report (UFSAR), analyses are performed for each reload cycle to ensure that a peak enthalpy of 280 cal/g is not exceeded. Furthermore, any rods that exceed a value of 170 cal/g are assumed to fail. The number of failed rods for ATRIUM 10XM supported by the Alternative Source Term (AST) CRDA dose assessment for BSEP is 986.

Analyses have been performed using Framatome's NRC approved methodology to support the MELLLA+ LAR and the results from the reload analysis report (Reference 2) are summarized in Table 2-1.

Table 2-1 Summary of CRDA Results with Current Methodology Representative Criteria Cycle Peak Fuel Enthalpy (cal/g) 180.9 < 280 cal/g*

s 986 (Number of rods Number of Failed Rods 182 exceeding 170 cal/g) 2.1.2 Draft NRC Criteria Reference 3 is a NRC Draft Regulatory Guide intended to replace current regulatory criteria as well as the interim criteria of SRP Section 4.2 (Reference 1). The draft criteria from Reference 3 are summarized Table 2-2. For the PCMI cladding failure criteria, only the low temperature criteria are used in the evaluation. The low temperature PCMI criteria are conservative relative to the high temperature PCMI cladding failure criteria.

• The current regulatory guidance is to limit the peak fuel enthalpy to < 280 cal/g. For the licensing analyses submitted as part of the MELLLA+ LAR, a 230 cal/g limit has been utilized due to the emerging changes to RIA acceptance criteria. The use of the lower enthalpy limit is conservative with respect to the current licensing basis.

For Information Only Framatome Inc. ANP-3655NP Revision 0 Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa e 2-3 Table 2-2 Summary of Draft RIA Acceptance Criteria Figure 2-1 Excess Clad Peak Radial Ave Hydrogen, HEX Enthalpy (cal/g)

(wppm)

~ 117 150

> 117 406 - 53.8 ln(HEX)

Pellet Clad Mechanical Figure 2-2 Interaction (PCMI)

Excess Clad Peak Radial Ave Hydrogen, HEX Enthalpy (cal/g)

(wppm)

Fuel ~ 165 150 Cladding > 165 424 - 53.8 ln(HEX)

Failure Figure 2-3 Clad Differential Peak Radial Ave Pressure (Mpa) Enthalpy (cal/g)

High Cladding Temperature Failure l\P ~ 1.0 170 1.0 >l\P < 4.5 170-(l\P-1.0)*20 l\P ~ 4.5 100 Rod Failure Assumed if fuel temperature Fuel Melt anywhere in the pellet exceeds incipient fuel melting conditions.

1. Peak radial average fuel enthalpy < 230 cal/g.

2. A limited amount of fuel melt is acceptable Core provided it is restricted to: (1) fuel centerline Coolability region, and (2) less than 10% of pellet volume. For the outer 90% of the pellet volume, peak fuel temperature must remain below incipient fuel melting conditions.

For Information nly Framatome Inc. ANP-3655NP Revision 0 Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa e 2-4 200 oo

~ 175 u

g (0,150}

~,

(117,15 ))

-~ 150 c:: Clad ~ing Failure C.

] 125

....C w

(aHfa il=406 - 5 3.81n[Hex )

ai

I 100 u.

C1J I~ ~

-i"----

Ill)

~ 75 Claddin ~ Intact i ,,__

l"CI

al"CI c::

so 7iiC1J 25 c..

0 0 100 200 300 400 500 600 700 800 Excess Cladding Hydrogen (wppm)

Figure 2-1 PCMI Failure Threshold for SRA Cladding Low Temperature

Information Only Framatome Inc. ANP-3655NP Revision 0 Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa e 2-5 200 175

~ (0,150) Clad ~ing Failun 111 u (165,l 50)

S 150 w

~

ii:

.E- 125

"" ~

111

....C

.c

(/.\I- fail=424- 53.Sln[He x])

w

] 100 u.

w ~

tll)

~

1 -- .,.,____

111

~

75 Claddinf Intact "t:I

~ so

.it:

111 w

a.

25 0

0 100 200 300 400 500 600 700 800 Excess Cladding Hydrogen (wppm)

Figure 2-2 PCMI Failure Threshold for SRA Cladding High Temperature

r Information Only Framatome Inc. ANP-3655NP Revision 0 Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa e 2-6 200 "iio 175 iii

~

~ 150 (0,170} (1.0.170\

~ Claddin1 Failure

~ .......

ii:

C.

] 125

....C w ~

] 100

~

LL QJ b.O ra {4.5,100}

cii 75 Jt iii Cladding Intact

ara so a::

ra

~ 25 0

0 1 2 3 4 5 6 Cladding Pressure Differential (MPa)

Figure 2-3 High Temperature Cladding Failure Threshold

For Information Only Framatome Inc. ANP-3655NP Revision 0 Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa e 2-7 2.1.3 System Pressure and CPR The draft regulatory guidance (Reference *3) as well as SRP4.2 (Reference 1) maintain the acceptance criteria for the CRDA with respect to system pressure and CPR. These criteria for the CRDA are summarized in Table 2-3.

Table 2-3 Summary of Pressure and CPR criteria for CRDA Evaluation System pressure The maximum reactor coolant system pressure should be limited to the value that will cause stresses to not exceed Emergency Condition (Service Level C), as defined in Section Ill of the ASME Boiler and Pressure Vessel code

.:: 5% power Rod failure when heat flux exceeds thermal design limits (critical power ratio)

The impact on system pressure was evaluated in Section 7.8 of Reference 8. The evaluation concluded that there is a local pressure increase in a few assemblies, however there is little change in the core system pressure in either the startup range or the power range. Therefore, the CRDA would not result in a reactor pressure which would cause increased stress to exceed the "Service Level C" ASME Boiler and Pressure Vessel Code.

The CPR response was evaluated in Section 7.7 of Reference 8 at various power levels to demonstrate that the potential number of rod failures would be [

] The Reference 8 evalLJation was performed on a BWR-4 liQensed at EPU conditions. This analysis was supplemented in the response to RAl-7 in Reference 10 to address [

] (Reference 11 ).

For information Only Framatome Inc. ANP-3655NP Revision 0 Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa e 2-8 2.2 Core Coo/ability This section addresses the core coolability criteria 1 and 2 of Table 2-2.

Core coolability criterion 1 is addressed by limiting the peak radial enthalpy to 230 cal/g. The results provided in Table 2-1 demonstrate that this criterion is met for the Brunswick ATRIUM 10XM core.

To address core coolablity criterion 2, a fuel melt curve was established utilizing the R0DEX4 methodology (Reference 6). The R0DEX4 code was used to establish the steady state pellet radial power profile as a function of exposure. [

]

(Definition of prompt pulse is consistent with SRP Section 4.2 (Reference 1) Appendix B, and is the radial average fuel enthalpy rise at the time corresponding to one pulse width after the peak of the prompt pulse).

[

]

As a consequence of the buildup of fissile plutonium isotopes due to the resonance capture of epithermal neutrons by U238 at the pellet surface, the pellet radial power profile becomes increasingly peaked at relatively high exposures. The temperature versus enthalpy relationship for U02 is defined in the R0DEX4 methodology. Given this relationship, a fuel melt enthalpy is determined. [

] The resulting fuel melt threshold is provided in Figure 2-4.

For Information Only Framatome Inc. ANP-3655NP Revision 0 Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa e 2-9 Figure 2-4 Maximum Radial Prompt Average Enthalpy versus Rod Exposure The current Framatome CRDA methodology (Reference 4) is based on adiabatic conditions. It is well understood that the pellet heats up in a nearly adiabatic condition during the power .

deposition; therefore variations in the gap thermal conductivity do not have a significant impact on the peak pellet temperature. [

] The pellet radial temperature profile peaked at the R0DEX4 melting temperature is shown in Figure 2-5.

For Information Only Framatome Inc. ANP-3655NP Revision 0 Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa e 2-10 Figure 2-5 Radial and Exposure Dependence of the Pellet Temperature Distribution

[

]

The Framatome COTRANSA2 (Reference 7) simulated startup range rod drops with ATRIUM 10XM fuel were evaluated. The enthalpy at the time corresponding to one pulse width after the peak of the prompt pulse was compared to the COTRANSA2 final enthalpy [

]

For Information Only Framatome Inc. ANP-3655NP Revision 0 Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa e 2-11

[

]

2.3 CRDA Fuel Rod Failure Evaluation As discussed in the previous section, maintaining a radial average enthalpy less than [

] The draft RIA criteria evaluated in this report includes rod failure thresholds for pellet clad mechanical interaction and high temperature. The following subsections address these criteria as well as adjustments to the number of calculated rod failures to address the impact of including transient fission gas release within the Brunswick licensing basis.

2.3.1 PCMI Cladding Failure Criteria The approved methodology for the current licensing basis at Brunswick (Reference 4) is based on a two-dimensional (r-z) geometry in which the core is divided into three zones. The currently approved methodology (XN-NF-80-19) parametrized rod drops such that the deposited enthalpy is a look up function based on static rod worth and peaking factors. Framatome has developed and submitted a new methodology (Reference 8 ) which is based on the AURORA-B methods which includes a 3D kinetics solution for the rod drop. (The terms XN-NF-80-19 and AURORA-B will be used to identify the methodologies.) The results of the evaluation with the XN-NF-80-19 methodology are provided in Table 2-4 which indicates fuel failures. The AURORA-B results for the same cycle are illustrated in Figure 2-6. (The PCMI failure threshold of Reference 3 was added to the results from the AURORA-B LTR.)

A direct one to one comparison is not straight forward. However, the maximum deposited enthalpy with the XN-NF-80-19 methodology is similar between Brunswick and the sample plant used in the AURORA-B LTR (Reference 8). The results in Figure 2-6 indicate an approximate margin of [ ] is maintained to the PCMI failure thresholds.

For Information Only Framatome Inc. ANP-3655NP Revision 0 Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa e 2-12 Additional comparisons were made between the sample plant core and the Brunswick Unit 1 Cycle 19 core.

Table 2-4 Summary of Sample Plant CRDA Results with XN-NF-80-19

• Methodology

• Criteria Peak Fuel Enthalpy (cal/g) 187.0 < 280 cal/g

< 2000 (Number of Number of Failed Rods 364 rods exceeding 170 cal/g)

• Dropped rod worth:

The MICROBURN-B2 simulator (Reference 5) was used to determine dropped rod worths. A comparison of dropped rod worths at 68F was made between the Brunswick Unit 1 Cycle 19 Core and the Sample Plant. The five highest rod worths above [ ] are provided as a function of time in cycle in Table 2-5 .

Table 2-5 Highest Dropped Rod Worth Comparison The Brunswick cycle has higher dropped rod worths at BOC and PHEX reactivity than the Sample plant. However the Sample plant has a significantly higher EOC rod worths. As the core exposure increases the values of the delayed neutron fraction (13) decreases such that the amount of reactivity insertion to reach prompt criticality decreases. [

]

• The number of rod failures was conservatively assigned to be all rods in each assembly with a rod that exceeded 170 cal/g.

For Information Only Framatome Inc. ANP-3655NP Revision 0 Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa e 2-13

[

] With consideration of 13, the sample plant has a higher insertion of reactivity relative to prompt critical.

Cladding Hydrogen Content:

The high worth BOC rod drops for BRK1-19 occur in interior locations with a combination of fresh and once burned fuel. The approved hydrogen model of Reference 9 was used in the process of establishing the PCMI failure thresholds. The minimum hydrogen dependent failure threshold [

] of each assembly. For the rod drops at peak, the minimum hydrogen dependent failure threshold is [

] away from the dropped rod.

Given that the maximum deposited enthalpy values with the XN-NF-80-19 methodology are similar between the Brunswick cycle and the sample plant, the dropped rod worth's between the plants are similar, and hydrogen dependent cladding failure thresholds are similar it is reasonable to conclude that the Brunswick cycle would not exceed the PCMI failure threshold or that it would only be exceeded by a small amount.

Based on the qualitative comparison of the BSEP analysis to that for the sample plant of Reference 8 it is concluded that for BRK1-19 demonstration cycle [

]

For Information Only Framatome Inc. ANP-3655NP Revision 0 Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa e 2-14 Figure 2-6 Prompt Enthalpy Rise versus Cladding Hydrogen Content with AURORA-8 Methodology

For Information Only Framatome Inc. ANP-3655NP Revision O Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa e 2-15 2.3.2 High Temperature Failure Threshold The current approved methodology does not provide a direct method for addressing this failure.

The high temperature failure criteria were evaluated in Reference 8 against SRP 4.2 Appendix B criteria and the results are provided in Figure 2-7. No high temperature failures were identified against the SRP 4.2 criteria. An evaluation against the high temperature threshold of DG-1327 was included in Reference 1O and is provided in Figure 2-8. Figure 2-8 provides the maximum enthalpy in the [ ]

The maximum total enthalpy for the drops is slightly more than [ ] cal/g (Table 2-6).

A conservative assumption would be that four assemblies had total enthalpy of [

] The conservatism of this assumption is supported since the average total enthalpy is less than [ ] cal/g and the results presented in Figure 2-8 indicate no failures.

Table 2-6 Total Deposited Enthalpy for Peak and Average Rod

[

l

For Information Only Framatome Inc. ANP-3655NP Revision 0 Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa e 2-16 Figure 2-7 Total Enthalpy versus High Temperature Failure Threshold (SRP4.2 AppB)

Figure 2-8 Total Enthalpy versus High Temperature Failure Threshold (DG-1327)

For Information Only Framatome Inc. ANP-3655NP Revision 0 Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa e 2-17 2.3.3 Release Fraction Scaling The dose consequence for the CRDA determined for rated conditions at Brunswick are summarized in the BSEP UFSAR. The current licensing basis dose evaluation allows 986 ATRIUM 10XM rods to fail. (Within this section the dose scaling is only completed for DG-1327 release terms.)

A component of the draft acceptance criteria is revised release fractions proposed to account for transient fission gas release (TFGR). The transient release terms (from Reference 3) expressed as a fraction are:

Peak Pellet BU< 50 GWd/MTU: TFGR = =-[(_0._26_*_LiH_)_-_13-=] .:: 0 100 Peak Pellet BU.:: 50 GWd/MTU: TFGR = =-[(_O._26_*_Li_H_)_-_5~] .:: 0 100

For Information Only Framatome Inc. ANP-3655NP Revision 0 Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa e 2-18

Where, TFGR is transient fission gas release (must be .:: 0) i1H fuel enthalpy increase (cal/g)

Three multipliers are established in Reference 3 to be applied to the above TFGR term:

Group Multiplier Applied to Stable long lived isotopes 1.0 Kr-85 (e.g.,Kr-85)

Cs-134 and Cs-137 1.414 Alkali Metals Short-lived radioactive 0.333 Iodine's, nobles, halogens isotopes (i.e., 1-131, 1-132, I-133, 1-135) and xenon and Krypton noble gases except Kr-85 (i.e., Xe-133, Xe-135, Kr-85m, Kr-87, Kr-88)

The transient release term is combined with the existing steady state release fraction to produce revised release fractions for the CRDA.

The steady state release fractions utilized for the BSEP CRDA licensing basis are:

Other Other Alkali 1-131 Kr-85 Nobles Halogens Metals 0.10 0.10 0.10 0.10 0.12

For Information Only Framatome Inc. ANP-3655NP Revision O Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa e 2-19 To account for the inclusion of the TFGR within the release fractions, a conservative approximat_ion of the axial enthalpy shape was utilized to determine the increase in the release for a rod based on the maximum deposited enthalpy and establish modified rod release fractions. The axial enthalpy shape is assumed to be [

] remainder of the nodes. Based on a review of rod drop evaluations this assumption provides a conservative representation of the total enthalpy deposited in the fuel rod for evaluating the transient fission gas release.

An example of the axial enthalpy distribution for eight rod drops is shown in Figure 2-9. The corresponding TFGR fractions for the eight rod drops based on the deposited enthalpy are given in Figure 2-10. A comparison of the total gas release based on the actual enthalpy to that

[ ] for low burnup fuel(< 50GWd/MTU) is provided in Table 2-7.

Table 2-7 Actual TFGR Fraction versus [ ] Basis

For Information Only Framatome Inc. ANP-3655NP Revision 0 Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa e 2-20 Figure 2-9 Axial Enthalpy Profile for Eight Representative Rod Drops Figure 2-10 Nodal Transient Fission Gas Release Fractions

For Information Only Framatome Inc. ANP-3655NP Revision 0 Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa e 2-21 The total rod release fraction for a given nuclide group can then be reformulated as:

Where,

[

]

Two steady state release fractions are used in the BSEP evaluation: 0.1 O for non-Alkali metals and 0.12 for Alkali metals. Since Krypton 85 uses the smaller steady state release fraction in the BSEP licensing basis and Cesium has the largest group multiplier, the TFGR term that will have the largest impact will be either that for Cs (Alkali Metals) or the Krypton 85. [

]

For Information Only Framatome Inc. ANP-3655NP Revision O Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa e 2-22 Krypton 85:

Alkali Metals:

The largest RFI occurs from the Alkali metals with a multiplier of 1.414. Therefor the RFI determined based on Alkali metals will be used for all isotopes.

[The number of rod failures can be increased by this factor for evaluation with respect to the J

BSEP current licensing basis. (This term is fuel pin specific based on the enthalpy increase in a specific fuel pin.) For this comparative evaluation, the maximum pin enthalpy increase is assumed for all rods.

The RFI is bundle dependent based on the maximum deposited enthalpy and bundle exposure for this comparative ~valuation.

The application of the RFI factors is provided in Section 2.4.

For Information Only Framatome Inc. ANP-3655NP Revision O Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa e 2-23 2.4 Rod Failure Assessment From Section 2.3.1 it is determined that it is unlikely there are PCMI failures for this cycle. [ *

]

From Section 2.3.2 it is assumed that [

]

For the release fraction it assumed that half of the failures are below 50 GWd/MT. This is reasonable in that assemblies around the rod include lower exposed assemblies with sufficient reactivity to result in deposited enthalpies of this magnitude. Using the formulation from Section 2.3.3 the following RFls are tabulated in Table 2-8. (Equivalent modified release fractions are provided in Table 2-10 along with the base release fractions from the BSEP UFSAR.)

Table 2-8 Enthalpy and Exposure Dependent RFI Factors These RFls are then applied to the assigned rod failures assuming half are below 50 GWd/MT:

Table 2-9 Revised Rod Failure Count The conservative estimate of rod failures is [ ] from PCMI.

Assuming that half of the rods have a burnup >50GWd/MT and applying the appropriate release scaling factor an equivalent of [ ] rods fail with respect to the current BSEP CRDA dose consequence evaluation which remains below the allowed 986 ATRIUM 10XM rod failures. The current radiological consequences determined for BSEP are provided in Table 2-11 along with

For Information Only Framatome Inc. ANP-3655NP Revision 0 Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa e 2-24 the fraction of the regulatory limit. The dose consequences for the CRDA are less than 6% of the regulatory limits.

Table 2-10 Enthalpy and Exposure Dependent Total Release Fractions Other Other Alkali 1-131 Kr-85 Nobles Halogens Metals BSEP UFSAR 0.10 0.10 0.10 0.10 0.12 Table 2-11 BSEP CRDA Radiological Consequences TEDE Dose (REM)

Receptor Location CR EAB LPZ BSEP AST Dose EPU 0.28 0.27 0.22 Allowable TEDE Limit 5 6.3 6.3 Fraction of Limit 0.056 0.043 0.035

For Information Only Framatome Inc. ANP-3655NP Revision 0 Brunswick MELLLA+ CRDA Asse;Ssment with Draft Criteria Pa e 2-25 2.5 Summary of Inherent Conservatisms The CRDA evaluation with Framatome's current approved methodology and BSEP current licensing basis resulted in an acceptable number of fuel failures (Table 2-1). With the evaluation of the CRDA in consideration of the draft criteria, the number of failures would increase with the currently approved methodology (Reference 4). However with the use of currently submitted methodology (Reference 8), the comparative evaluation does not indicate a significant increase in the number of rod failures.

This comparative evaluation of the rod drop involves numerous conservatisms:

The actual dose consequence evaluation contains conservatism in the calculation and in the margin to the regulatory requirement.

For information Only Framatome Inc. ANP-3655NP Revision O Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa e 2-26 2.6 Conclusion This document has addressed the impact of the draft acceptance criteria similar to that of Reference 3 and Reference 1 in the startup range if it were to be implemented during BSEP MELLLA+ operation. In summary, it was found that:

It is therefore concluded that continued evaluation of BSEP reload cycles at the proposed MELLLA+ conditions with the currently approved methodology will continue to ensure that the current licensing basis and dose limits are met. Furthermore, based on the results of the evaluations above, it is reasonable to conclude that the BSEP will comply with the proposed new acceptance criteria for the CRDA at MELLLA+ conditions with the implementation of new methodology for evaluating the CRDA.

This response to RAI SPB-RAl-2 for the Brunswick MELLLA+ LAR demonstrates that the new draft criteria can be met for the CRDA analysis for BSEP Units 1 and 2 if the criteria* were to be issued.

• It is anticipated that minor changes will occur in the criteria in response to public comment on DG-1327. No significant changes are anticipated that would alter the conclusion of this response.

For Information Only Framatome Inc. ANP-3655NP Revision 0 Brunswick MELLLA+ CRDA Assessment with Draft Criteria Pa e 3-1

3.0 REFERENCES

1. NUREG-0800, U.S. Nuclear Regulatory Commission, Standard Review Plan, Section 4.2, Fuel System Design, Revision 3, March 2007.

2. ANP-3280P Revision 1, Brunswick Unit 1 Cycle 19 MELLLA+ Reload Safety Analysis, AREVA Inc., May 2016.

3. DG-1327, Draft Regulatory Guide, Pressurized Water Reactor Control Rod Ejection and Boiling Water Reactor Control Rod Drop Accidents, US NRC November 2016 (ML16124A200)

4. XN-NF-80-19(P)(A), Volume 1 Supplements 1 and 2, Exxon Nuclear Methodology for Boiling Water Reactors- Neutronics Methods for Design and Analysis, Exxon Nuclear Company, March 1983.

5. EMF-2158(P)(A) Revision 0, Siemens Power Corporation Methodology for Boiling Water Reactors: Evaluation and Validation of CASM0-4/MICROBURN-B2, Siemens Power Corporation, October 1999.

6. BAW-10247PA Revision 0, Realistic Thermal-Mechanical Fuel Rod Methodology for Boiling Water Reactors, AREVA NP, February 2008.

7. ANF-913(P)(A) Volume 1 Revision 1 and Volume 1 Supplements 2, 3 and 4, COTRANSA2: A Computer Program for Boiling Water Reactor Transient Analyses, Advanced Nuclear Fuels Corporation, August 1990.

8. ANP-10333P Revision 0, AURORA-B: An Evaluation Model for Boiling Water Reactors; Application to Control Rod Drop Accident (CRDA), AREVA Inc., March 2014.

9. BAW-10247PA Revision O Supplement 1P-A, Realistic Thermal-Mechanical Fuel Rod Methodology for Boiling Water Reactors Supplement 1: Qualification of RODEX4 for Recrystallized Zircaloy-2 Cladding, April 2017.

10. ANP-10333Q1 P, Revision 0, AURORA-B: An Evaluation Model for Boiling Water Reactors; Application to Control Rod Drop Accident (CRDA) Responses to NRG Request for Additional Information, April 2017.

11. NED0-10527, Supplement 1, Rod Drop Accident Analysis for Large Boiling Water Reactors, Class 1, General Electric, San Jose, CA.