ML24005A102
| ML24005A102 | |
| Person / Time | |
|---|---|
| Issue date: | 01/05/2024 |
| From: | Shawn Campbell, Michael Salay Office of Nuclear Regulatory Research |
| To: | |
| References | |
| Download: ML24005A102 (1) | |
Text
High Burnup Fuel Source Term Accident Analysis Boiling-Water Reactor Follow-On Calculations Public Workshop January 9, 2024 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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3 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
4 Illustration of BWR Modeling Practices Area with refined modeling Peach Bottom
5 New BWR Main Steam Line (MSL) Modeling open 2 to 4 SRVs per MSL 3 RCIC (MSL A) 10 HPCI (MSL B)
MSIV #1 MSIV #2 TSV to TCVs and turbine Vented to environment Condenser Containment boundary RPV steam dome All 4xMSLs modeled separately The reported source term fractions in the steam line are averaged airborne fission products in the green portion.
Condenser Vented to the environment For each BWR, the Main Steam Lines were broken up into finer nodalization
6 Radionuclide Group RG1.183 (rev0)
RG1.183 (rev1)
SAND2023 Pool (SAND2023 Table 5-16)
Containment (SAND2023 Table 5-16)
Steam Line (Preliminary 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 BWR Source Term (ST) Inventory Fractions - Early In-Vessel
BWR Example Fission Product (FP) Concentrations (C0) 7 C0 =ST/ Vol
- 2023 Follow-on calculations do not include FPs retained in the suppression pool
- 2023 Follow-on calculations do not include FPs retained in the suppression pool FP Concentration (x 10-5)
FP Concentration (x 10-5)
8 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.
Potential Approach to BWR Pathway-Specific Source Term
9 C0 =ST/ Vol 2023 Follow-on calculations do not include FPs retained in the BWR suppression pool 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
Example HBU Inventories 10 Radionuclide Group BWR (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 (MWd/MTU) 36.2 41.4 43.5 48.3 Avg. Assembly discharge BU (MWd/MTU) 52.6 58.0 60.7 71.6 Initial Enrichment (%)
4.45 5.30 4.65 5.25 Power (MWt) 4016 4016 2893 2893 Cycle Length (months) 24 24 18 24
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 12
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 13
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