ML23346A110
| ML23346A110 | |
| Person / Time | |
|---|---|
| Issue date: | 11/16/2023 |
| From: | Shawn Campbell, Michael Salay NRC/RES/DSA/FSTB |
| To: | |
| References | |
| Download: ML23346A110 (1) | |
Text
High Burnup Fuel Source Term Accident Analysis Boiling-Water Reactor Follow-On Calculations ACRS Radiation Protection And Nuclear Materials Subcommittee Briefing November 16, 2023 Shawn Campbell and Michael Salay Fuel & Source Term Code Development Branch Division of Systems Analysis Office of Nuclear Regulatory Research 1
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 scenarios and pathways bypass the suppression pool (e.g., 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.
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Source Term Methodology Early Vessel Late Fuel heat up Core FP Release and Containment MCCI/FP containment Breach containment Integrated Clad oxidation relocation Transport Leakage Release failure? failure?
Analysis (e.g., L3PRA, Containment SOARCA, In-Vessel Source Term Ex-Vessel (ST)
Fukushima)
Mechanistic Modeling FP Inventory FP removal mechanisms () Leak Rate ()
() e.g., Sprays/natural deposition User Specified User Specified Simplified Modeling Simplified Modeling Regulatory Source Containment Term C0 =ST/ Vol C t = C0 exp() FP release = C Dose Calculation Source Term (ST)
Analysis (for DBA) 3
Illustration of BWR Modeling Practices Area with refined modeling Peach Bottom 4
New BWR Main Steam Line (MSL) Modeling RPV steam dome For each BWR, the Main Steam Lines were broken up into finer nodalization Containment 2 to 4 SRVs 3 RCIC (MSL A) boundary per MSL 10 HPCI (MSL B)
MSIV #2 TSV to TCVs and turbine MSIV #1 open Vented to the The reported source term Condenser environment fractions in the steam line are averaged airborne fission All 4xMSLs modeled Vented to Condenser separately environment products in the green portion.
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BWR Source Term (ST) Inventory Fractions - Early In-Vessel Pool Containment Steam Line Radionuclide RG1.183 (rev0) RG1.183 (rev1) SAND2023 (SAND2023 (SAND2023 (Preliminary Group Table 5-16) Table 5-16) Follow-on Calcs)
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-11 Ce Group 5.00E-04 <1.0e-6 <1.0e-6 <1.0e-6 <1.0e-6 8.4E-12 6
BWR Example Fission Product (FP) Concentrations (C0)
C0 =ST/ Vol FP Concentration (x 10-5) FP Concentration (x 10-5)
- 2023 Follow-on *2023 Follow-on calculations do not include calculations do not include FPs retained in the FPs retained in the suppression pool suppression pool 7
BWR/PWR Example Containment Concentrations Halogen (Iodine) x 1E-5 C0 =ST/ Vol 2023 Follow-on calculations do not include FPs retained in the BWR BWR PWR suppression pool Alkali Metals (Cesium) x 1E-5 Typical containment volumes from Figure 4.1-1 in NUREG/CR-6042, Rev. 2 8
Example HBU Inventories Radionuclide Group BWR (Bq) BWR (%) -> HBU PWR (Bq) PWR (%) -> HBU Halogens (I) 3.54E19 <1% 2.53E19 <1%
Alkali Metals (Cs) 4.46E18 +7% 3.09E18 +5%
Chalcogen (Te) 1.16E19 <1% 8.35E18 <1%
GE14 10x10 GE14 10x10 W 17x17 W 17x17 Core Avg. end of cycle BU 36.2 41.4 43.5 48.3 (MWd/MTU)
Avg. Assembly discharge BU 52.6 58.0 60.7 71.6 (MWd/MTU)
Initial Enrichment (%) 4.45 5.30 4.65 5.25 Power (MWt) 4016 4016 2893 2893 Cycle Length (months) 24 24 18 24 9
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.
- Preliminary investigation of fission product inventories show limited effect for high burnup/high-assay low-enriched uranium (HBU/HALEU)fuels.
- Potential application of MELCOR to inform better estimates of fission product removal mechanisms in the simplified tools for regulatory applications and analysis where appropriate.
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Backup Slides 11
Acronyms Bq Becquerel MWt Megawatt thermal BWR boiling-water reactor PWR pressurized water reactor DBA design-basis accident RCIC reactor core isolation cooling FP fission product RG (NRC) regulatory guide GE General Electric RPV reactor pressure vessel HALEU high-assay low-enriched uranium SOARCA State-of-the-Art Reactor HBU high burnup Consequence Analyses HPCI high pressure coolant injection SRV safety relief valve MSIV main steam line isolation valve ST source term MSL main steam line TCV turbine control valve GWd/MTU gigawatt-days per metric ton of TSV turbine stop valve uranium W Westinghouse 12