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Application of Modified ART Mod 2 Code to Fission Product Behavior
Analysis for Spent Fuel Pool of Nuclear Power Plant
Corresponding author email*: [email protected]
Chulalongkorn UniversityThailand Institute of Nuclear
Technology (Public Organization)
TM on the Phenomenology, Simulation and Modelling of Accidents in Spent Fuel PoolsIAEA Headquarters, Vienna, Austria
2 – 5 September 2019
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W. Vechgama*, K. Silva, C. Kittasin, S. Rassame
Overview
ASEAN Network on Nuclear Power Safety Research
Fission product behavior analysis
R&D activities
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Severe accident of NPP
Regional strategy for accident management
Background and Motivation
TINT & CU Fission product behavior during severe accident
Containment vessel
Reactor vessel
ART Mod 2 Code
Modified ART Mod 2
Spent fuel pool (SFP)
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3To help understand the overall consequences of fission product deposition and release during severe accident of nuclear power plants
Objective
The objective of this study is to assess fission product behavior in the SFP to fulfill the gap of fission product analysis.
• The Robert Emmett Ginna Nuclear Power Plant➢Geometry conditions of the SFP
➢Boundary conditions of the SFP
• Compounds of Cs-137➢Long term effect of Cs-137
➢Gas form of CsI
➢Aerosol form of CsOH
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Modified ART Mod 2 Code
Condensation
Adsorption
Gravitational Settling
Brownian diffusion
Diffusiophoresis
Thermophoresis
Gas deposition
Aerosol deposition
Deposition on wall
Deposition on floor
Remaining
Wall
Floor
Gas Aerosol
Gas remaining Aerosol remaining
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Simulation ConditionsThe SFP of the Robert Emmett Ginna NPP is selected as a representative accident because of;
• PWR type which is the same type of the neighboring NPPs of ASEAN,
• Publicly available reports on postulated accidents in case of LOCA or complete draining in the SFP.
General information• Ontario, New York, USA• 2 loops PWR, Westinghouse• Capacity of 490 MW(e)
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https://en.wikipedia.org/wiki/R._E._Ginna_Nuclear_Power_Plant
Simulation Conditions
• CsI in gas form and CsOH in aerosol form are dominant cesium compounds in the SFP analysis.
• Cesium compounds in different forms can be evaluated behavior using existingmodels of modified ART Mod 2.
• The study divided to two cases to understand release behavior differences between gas and aerosol. ➢Case 1: CsI in gas form
➢Case 2: CsOH in aerosol form
Source term parameters Case 1 Case 2Source term type CsI CsOHForm Gas AerosolSize [µm] - 50-70Amount [Ci] 1.48×107 1.48×107
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Simulation Conditions
Environment volume
SFP volume
Source term
volume
Geometry parameters DataLength [ft] 43.0Width [ft] 22.2Hight [ft] 41.7Volume [ft3] 3.98×104
Geometry parameters of the SFP• Nodalization for modified ART Mod 2 code
• The studies assumed that the SFP is open to the environment.
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Simulation Conditions
• Thermal hydraulic parameters of the SFP in case of LOCA or complete draining in the SFP are selected because this is period of fission product release.
Thermal hydraulic parameters Data
Rate of temperature increase
during boiling [°C/hr]
~7
Self-sustaining oxidation
temperature [°C]
~900
Cutoff oxidation temperature [°C] ~1900
Pressure [MPa] 0.101
Boil off rate [ft3/hr] 13
Complete
draining
of the
SFP
Self-
oxidation
reaction
Temperature of heat decay and oxidation reaction of the SFP 9
Starting point of release at 18,760 seconds
Result and Discussion
CsI release at 18,760 seconds
Adsorption
Release into environment
at 17 days
Remaining in
the SFP
Case 1: CsI in gas form• Majority of CsI is released from the
SFP into environment in 17 days.
• The release characteristic is consistence to measurement data set of Cs and I of the Fukushima nuclear accident.
• In the Fukushima accident, the major part of the release is estimated to be within 19 days after the accident starts. Case 1
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Result and Discussion
Case 2: CsOH in aerosol form• Almost no CsOH is released from the
SFP into environment.
• Brownian diffusion is dominant for CsOH at high temperature due to increases of turbulence flow.
• There are no diffusiophoresis and thermophoresis due to assuming no difference of wall temperature and gas temperature because of the limitation of data of temperature.
CsOH release at
18,760 seconds
Brownian diffusion
Gravitational settling
Release into
environment
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Result and Discussion
• From experiment of fission product, CsOH can also exist in form gas because of reaction between CsI and steam.
• Therefore, there is a potential of a larger release of CsOH into environment when compared to the simulation results.
• Accuracy of the results can be further increased by considering the source term ratio of gas and aerosol, difference between wall and ambient temperatures, and chemical reactions appropriately.
• From our previous study noted the possibility of having different cesium and iodine compounds due to chemical reactions, such as cesium molybdate (Cs2MoO4), cesium telluride (Cs2Te), methyl iodide (CH3I), iodine pentoxide (I2O5).
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ConclusionModified ART Mod 2 code was used to assess cesium compounds behavior of the LOCA or complete draining in SFP of the Robert Emmett Ginna Nuclear Power Plant.
• Majority of CsI gas tend to be released into environment within 17 days which resembles the release characteristic of the Fukushima Nuclear Accident in early period.
• Brownian diffusion is dominating CsOH aerosol deposition at high temperature because of increase of turbulence flow.
• Modified ART Mod 2 code can capture the trend of release of CsI gas but not CsOHaerosols because of assuming no difference of wall and gas temperatures.
• Total cesium compounds releases and retention can be more accurately estimated if source term ratio of gas and aerosol, difference between no difference of wall and gas temperatures, and chemical reactions are appropriately considered.
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Future Plan
• Modified ART Mod 2 code should be adjusted to accurately evaluate cesium compounds aerosol.
• The combination of radioactive releases from the RPV and the SFP should be considered to identify mass balance and fission product release.
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Thank you for your kind attention
TM on the Phenomenology, Simulation and Modelling of Accidents in Spent Fuel PoolsIAEA Headquarters, Vienna, Austria
2 – 5 September 2019
Q & A15
W. Vechgama*, K. Silva, C. Kittasin, S. Rassame
Corresponding author email*: [email protected]