ML24323A173
| ML24323A173 | |
| Person / Time | |
|---|---|
| Issue date: | 11/18/2024 |
| From: | Shawn Campbell, Michael Salay Office of Nuclear Regulatory Research |
| To: | |
| References | |
| Download: ML24323A173 (1) | |
Text
High Burnup Fuel Source Term Accident Analysis Boiling-Water Reactor Follow-On Calculations ACRS FUELS, MATERIALS, AND STRUCTURES SUBCOMMITTEE BRIEFING November 19, 2024 Shawn Campbell and Michael Salay Fuel & Source Term Code Development Branch Division of Systems Analysis Office of Nuclear Regulatory Research 1
Outline
- Background and Motivation
- Source Term Methodology
- Multi-region source terms for BWRs
- Example HBU Inventories
- Steam line removal rates for downstream codes 2
Background and Motivation
- The High Burnup (HBU) Peer Review panelists commented on the potential impact of the suppression pool on the containment source term.
- Table 5-16 of SAND2023-01313 provides the boiling-water reactor (BWR) containment release fractions including and excluding the suppression pool.
- Supplemental investigations following the peer review in BWRs:
- Investigate fission product concentration variation between different regions of the reactor system and containment since some release pathways bypass the suppression pool (i.e., main steam line).
- Modified the two (Peach Bottom, Grand Gulf) full-scale BWR input decks to better capture aerosol behavior in the containment and steam line.
- Performed a set of BWR source term calculations.
- Proposed methodology for a multi-region (pathway-specific) BWR source term.
3
4 In-Vessel Ex-Vessel Fuel heat up Clad oxidation Core relocation Early containment failure?
Vessel Breach Late containment failure?
MCCI/FP Release Containment Source Term (ST)
Leak Rate ()
FP Inventory
()
Dose Calculation C0 =ST/ Vol Containment Leakage FP Release and Transport C t = C0 exp()
FP release = C FP removal mechanisms ()
e.g., Sprays/natural deposition Containment Source Term (ST)
Integrated Analysis (e.g., L3PRA,
- SOARCA, Fukushima)
Regulatory Source Term Analysis (for DBA)
Mechanistic Modeling User Specified Simplified Modeling User Specified Simplified Modeling Source Term Methodology
Multi-Region Source Term for BWRs
- Containment Source Term (ST)
- Broke the source term into three parts:
- Suppression pool (SP)
- Containment atmosphere
- Main Steam Line (MSL)
- The first two STs are derived from SAND2023-01313 results
6 Illustration of BWR Modeling Practices Area with refined modeling Peach Bottom
7 New BWR Main Steam Line (MSL) Modeling The reported source term fractions in the steam line are averaged airborne fission products in the green portion.
For each BWR, the Main Steam Lines were broken up into finer nodalization
The release fractions in the steam line are for the green portion (downstream of first SRV, upstream of MSIV)
Airborne aerosols only, already takes into account the removal of fission products (for gap and early in-vessel phases)
Time averaged over each phase duration (i.e. gap, early in-vessel, etc.)
RADTRAD would take this as a constant concentration Steamline Release Phase Gap Release*
0.0h - 0.7h Early In-vessel* 0.7h -
7.4h Noble Gases 2.9e-5 1.1e-3 Halogens 5.6e-6 5.1e-5 Alkali Metals 5.1e-6 1.3e-5 Te Group 3.2e-6 2.7e-5 Ba/Sr Group 6.1e-7 2.4e-7 Ru Group
<1e-9 2.4e-7 Mo Group 3.3e-9 3.0e-6 Lanthanides
<1e-9
<1e-9 Ce Group
<1e-9
<1e-9
- inventory fraction held constant across the phase duration Proposed BWR Multi-Region Source Term
9 BWR Source Term (ST) Inventory Fractions
10 Radionuclide Group RG1.183 (rev0)
RG1.183 (rev1)
SAND2023 Pool (SAND2023 Table 5-16)
Containment (SAND2023 Table 5-16)
Steam Line (SAND2024-10674)
Noble Gases 9.50E-01 9.60E-01 9.50E-01 0.00E+00 9.50E-01 1.1E-03 Halogens 2.50E-01 5.40E-01 7.10E-01 6.50E-01 6.00E-02 5.1E-05 Alkali Metals 2.00E-01 1.40E-01 3.20E-01 3.10E-01 6.00E-03 1.3E-05 Te Group 5.00E-02 3.90E-01 5.60E-01 5.20E-01 3.80E-02 2.7E-05 Ba/Sr Group 2.00E-02 5.00E-03 5.00E-03 4.70E-03 3.00E-04 2.4E-07 Ru Group 3.00E-03 2.70E-03 6.00E-03 6.00E-03 7.40E-06 2.4E-07 Mo Group 3.00E-03 3.00E-02 1.20E-01 1.20E-01 1.00E-04 3.0E-06 Lanthanides 2.00E-04
<1.0e-6
<1.0e-6
<1.0e-6
<1.0e-6
<1.0e-9 Ce Group 5.00E-04
<1.0e-6
<1.0e-6
<1.0e-6
<1.0e-6
<1.0e-9 BWR Source Term (ST) Inventory Fractions - Early In-Vessel
BWR Example Fission Product (FP) Concentrations (C0) 11 C0 =ST/ Vol
- SAND2024-10674 calculations do not include FPs retained in the suppression pool
- SAND2024-10674 calculations do not include FPs retained in the suppression pool FP Concentration (x 10-5)
FP Concentration (x 10-5)
12 C0 =ST/ Vol Halogen (Iodine) x 1E-5 Alkali Metals (Cesium) x 1E-5 BWR/PWR Example Containment Concentrations BWR PWR Typical containment volumes from Figure 4.1-1 in NUREG/CR-6042, Rev. 2 SAND2024
Example HBU Inventories
- Fission Product Inventory (Inv)
- Created representative inventories for a high burnup core
- Used SCALE to generate inventories with representative fuel cycle
- Fuel & core designs based on SCALE ATF/HBU/EE Project 13
Example HBU Inventories - PWRs 14 Radionuclide Group Baseline Activity (Bq)
HBU/EE Activity (Bq)
Rel. Change
(%)
Halogens (I) 2.53E19 2.53E19
~0 Alkali Metals (Cs) 3.09E18 3.24E18 5
Chalcogen (Te) 8.35E18 8.33E18
~0 Input Data to Fuel Cycle Estimator Baseline HBU/EE Power (MWth) 2893 2893 Initial Enrichment (%)
4.65 5.25 Cycle Length (months) 18 24 Fresh / Once-burned / Twice-burned 56 / 56 / 45 72 / 72 / 13 Core Avg. end of cycle BU (MWd/MTU) 43.5 48.3 Avg. Assembly discharge BU (MWd/MTU) 60.7 71.6 Objective Increase cycle length from 18 months to 24 months Impact on Radionuclide Inventories
Example HBU Inventories - BWRs 15 Radionuclide Group Baseline Activity (Bq)
HBU/EE Activity (Bq)
Rel. Change
(%)
Halogens (I) 3.54E19 3.54E19
~0 Alkali Metals (Cs) 4.46E18 4.78E18 7
Chalcogen (Te) 1.16E19 1.15E19
~0 Input Data to Fuel Cycle Estimator Baseline HBU/EE Power (MWth) 4016 4016 Initial Enrichment (%)
4.45 5.30 Cycle Length (months) 24 24 Fresh / Once-burned / Twice-burned 316 / 316 / 132 260 / 260 / 244 Core Avg. end of cycle BU (MWd/MTU) 36.2 41.4 Avg. Assembly discharge BU (MWd/MTU) 52.6 58.0 Objective Reduce feed batch fraction Impact on Radionuclide Inventories
Removal Rates in the Steam Line
- FP removal mechanisms upstream of containment boundary
- For gap and early in-vessel phases, removal rates are already accounted for in SAND2024-10674 formulation
- After early-in vessel phase, question was raised how to account for removal in the long-term dose assessment with downstream codes
- Used existing NUREG2206 analysis to ascertain a reasonable removal rate in the steam line and documented results in RES/FSCB2024-01 16 ML24222A207
17 Total Containment Source Term Containment Source Term (ST)
Radionuclide Group Containment (SAND2023 Table 5-16)
Halogens 6.00E-02 Alkali Metals 6.00E-03 Te Group 3.80E-02 Radionuclide Group Steam Line (Preliminary Follow-on Calcs)
Halogens 5.1E-05 Alkali Metals 1.3E-05 Te Group 2.7E-05 No proposed change to process in calculating the dose.
Steam line ST table already takes FP deposition into account so credit should not be taken for deposition between the reactor vessel and first MSIV during early in-vessel phase.
Possible approaches after early in-vessel phase:
1.
Keep concentration constant 2.
Apply a removal rate informed by additional analyses BWR Multi-Region Source Term Removal Mechanism
Model MELCOR model from the SOARCA studies (NUREG/CR 7110 and 7155)
Reference:
J. Barr, S. Basu, H. Esmaili and M. Stutzke, Technical Basis for the Containment Protection and Release Reduction Rulemaking for BWRs with Mark I and Mark II Containments, Office of Nuclear Regulatory Research, US NRC, NUREG-2206, March 2018.
Case selections Note: 1) Two cases without water injection and five cases with water injection are selected.
Option Case 0
4 72 0
4 16 SP CST 230 240 No Yes 15 5
21' Throttle
@ 21 '
Continuo us Thermal seizure -
fraction open Seizure on #
cycles?
Open Cycle (10/20 psid)
Initial Switchov er PCPL PSP Yes No 1
1 X
X X
X X
X X
100%
Enabled X
WW X
X 1
3 X
X X
X X
X X
No Disabled X
WW X
X 2A 10 X
X X
X X
X X
X X
100%
Enabled X
WW DW X
X 2A 11 X
X X
X X
X X
X X
100%
Enabled X
WW DW X
X 2B 18 X
X X
X X
X X
X X
100%
Enabled 10/10 WW DW X
X 2B 16 X
X X
X X
X X
X X
100%
Enabled 20/-
WW DW X
X 2A 42 X
X X
X X
X X
X X
No Disabled X
WW DW X
X Notes 0 DC power means there is no RPV pressure control, so should start like a SBO and remains so 10/10 means both WW and DW cycle at 10 psid 20/- means allow WW cycling at 20 psid but DW is not cycling and remains open WW Level Control Injection Allow SRV stuck Mode Setpoint (psig)
Allow after RCIC Injection @ LH Location Setpoint Fail @ 700F DW Head Seal Availability (hr)
RCIC Availability (hr)
RCIC Suction Failure Temp (F)
Open SRV after RUN MATRIX REV 9 (10/15/2014) - Mark I Pre Core Damage Post Core Damage DC Power RCIC Operation Anticipatory Venting Flex Operation SRV Operation Containment Venting Proposed BWR Multi-Region Source Term 18
0 200 400 600 800 1000 1200 1400 1600 1800 0
10 20 30 40 50 60 70 80 Temperature [K]
time [hr]
Cases with water injection Cases without water injection Maximum MSL wall temperatures Proposed BWR Multi-Region Source Term Fraction of airborne halogens in steam line 19
Total halogens time-averaged airborne concentration Total alkali metals time-averaged airborne concentration 1.0E-12 1.0E-11 1.0E-10 1.0E-09 1.0E-08 1.0E-07 1.0E-06 1.0E-05 1.0E-04 1.0E-03 1.0E-02 1.0E-01 1.0E+00 Concentrations (fraction of inventory/m3) in MSLs, early in-vessel phase in MSLs, VB to 48 hrs in MSLs, 48 to 72 hrs in containment, early in-vessel phase in containment, VB to 48 hrs in containment, 48 to 72 hrs Note: The hollow marks indicate the cases where water injection to the RPV dome shroud did not occur 1.0E-12 1.0E-11 1.0E-10 1.0E-09 1.0E-08 1.0E-07 1.0E-06 1.0E-05 1.0E-04 1.0E-03 1.0E-02 1.0E-01 1.0E+00 Concentrations (fraction of inventory/m3) in MSLs, early in-vessel phase in MSLs, VB to 48 hrs in MSLs, 48 to 72 hrs in containment, early in-vessel phase in containment, VB to 48 hrs in containment, 48 to 72 hrs Proposed BWR Multi-Region Source Term 20
Proposed BWR Multi-Region Source Term
-10.0
-8.0
-6.0
-4.0
-2.0 0.0 2.0 0.0E+0 2.0E+4 4.0E+4 6.0E+4 8.0E+4 1.0E+5 1.2E+5 1.4E+5 1.6E+5 1.8E+5 ln (Conc/Conc0) (-)
Time (sec)
Regression of Concentrations of Halogens and Alkali Metals in MSLs Halogens Alkali Metals Regression: ln(conc/conc0) =-3.4E-5*t, (R square = 0.810) 21
Proposed BWR Multi-Region Source Term Containment Boundary Steam Line Source Term (ST) is a function of C0() =ST(t)/ Vol 22
Conclusions and Next Steps
- Refined modeling provides better estimation of fission product distribution in the steamline.
- Concentration in the steam line is distinct from that of containment.
- Significant retention of fission products were predicted in the suppression pool.
- A multi-region, pathway specific source term is being applied for BWRs in DG-1425 (RG1.183 rev2).
- Plan to apply MELCOR to inform better estimates of fission product removal mechanisms in containment for the simplified tools used in regulatory applications.
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Backup Slides 24
Acronyms Bq Becquerel BWR boiling-water reactor DBA design-basis accident FP fission product GE General Electric HALEU high-assay low-enriched uranium HBU high burnup HPCI high pressure coolant injection MSIV main steam line isolation valve MSL main steam line GWd/MTU gigawatt-days per metric ton of uranium MWt Megawatt thermal PWR pressurized water reactor RCIC reactor core isolation cooling RG (NRC) regulatory guide RPV reactor pressure vessel SOARCA State-of-the-Art Reactor Consequence Analyses SRV safety relief valve ST source term TCV turbine control valve TSV turbine stop valve W
Westinghouse 25
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