Application of Modified ART Mod 2 2 Code to Fis ission Product - - PowerPoint PPT Presentation

Application of Modified ART Mod 2 2 Code to Fis ission Product Behavior Analysis for Spent Fuel Pool of Nuclear Power Plant

Corresponding author email*: wasin@tint.or.th

Chulalongkorn University Thailand Institute of Nuclear Technology (Public Organization)

TM on the Phenomenology, Simulation and Modelling of Accidents in Spent Fuel Pools IAEA Headquarters, Vienna, Austria 2 – 5 September 2019

• W. Vechgama*, K. Silva, C. Kittasin, S. Rassame

Overv rview

ASEAN Network on Nuclear Power Safety Research Fission product behavior analysis R&D activities

Severe accident of NPP Regional strategy for accident management

Background and Motivation

☑ ☑

✇

To 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

Modified ART Mod 2 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

Sim imulation Conditions

The SFP of the Robert Emmett Ginna NPP is selected as a representative accident because

• f;
• 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)

Sim imulation 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 existing

models 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 2 Source term type CsI CsOH Form Gas Aerosol Size [µm]

• 50-70

Amount [Ci] 1.48×107 1.48×107

Sim imulation Conditions

Geometry parameters Data Length [ft] 43.0 Width [ft] 22.2 Hight [ft] 41.7 Volume [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.

Sim imulation 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

• f the

• xidation

Temperature of heat decay and oxidation reaction of the SFP

Starting point of release at 18,760 seconds

Result and Dis iscussion

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

• f 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

Result and Dis iscussion

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

Result and Dis iscussion

• 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).

Conclusion

Modified 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 CsOH

aerosols 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.

Future Pla lan

• 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.

Thank you for your kin ind attention

TM on the Phenomenology, Simulation and Modelling of Accidents in Spent Fuel Pools IAEA Headquarters, Vienna, Austria 2 – 5 September 2019

Q & A

• W. Vechgama*, K. Silva, C. Kittasin, S. Rassame

Corresponding author email*: wasin@tint.or.th