scholarly journals Source term estimation for the MARIA research reactor and model of atmospheric dispersion of radionuclides with dry deposition

Nukleonika ◽  
2020 ◽  
Vol 65 (3) ◽  
pp. 173-179
Author(s):  
Maciej Lipka
Keyword(s):  
Balance Equation ◽  
Dry Deposition ◽  
Nuclear Reactor ◽  
Research Reactor ◽  
Source Term ◽  
Atmospheric Dispersion ◽  
Source Term Estimation ◽  
Complicated Geometry ◽  
Radionuclide Activity ◽  
Plume Composition

AbstractSource term is the amount of radionuclide activity, measured in becquerels, released to the atmosphere from a nuclear reactor, together with the plume composition, over a specific period. It is the basis of radioprotection-related calculation. Usually, such computations are done using commercial codes; however, they are challenging to be used in the case of the MARIA reactor due to its unique construction. Consequently, there is a need to develop a method that will be able to deliver useful results despite the complicated geometry of the reactor site. Such an approach, based upon the Bateman balance equation, is presented in the article, together with the results of source term calculation for the MARIA reactor. Additionally, atmospheric dispersion of the radionuclides, analysed with the Gauss plume model with dry deposition, is presented.

A Research Reactor Source Term and Dose Results in the Event of a LOCA

2014 ◽  
Author(s):  
Charalampos Pappas ◽  
Andreas Ikonomopoulos ◽  
Athanasios Sfetsos ◽  
Spyros Andronopoulos ◽  
Melpomeni Varvayanni ◽  
...  
Keyword(s):  
Research Reactor ◽  
Source Term ◽  
Dispersion Model ◽  
Ventilation System ◽  
Atmospheric Dispersion ◽  
Reactor Core ◽  
Forecast Model ◽  
Scale Model ◽  
Continuous Reactor ◽  
Reactor Building

The present study discusses the source term derivation and dose result calculation for a hypothetical accident sequence in the Greek Research Reactor – 1 (GRR-1). A loss-of-coolant accident (LOCA) has been selected as a credible accident sequence. The source term derivation has been based on the GRR-1 confinement performance where the inventory has been computed assuming continuous reactor operation. A core damage fraction of 30% has been considered for the calculations while conservative core release fractions have been employed. The radionuclides released from the reactor core to the confinement atmosphere have been subjected to natural decay, deposition on and resuspension from various internal surfaces before being led to the release pathway. It has been assumed that an emergency shutdown is initiated immediately after the beginning of the accident sequence and the emergency ventilation system is also activated. Subsequently, the source term has been derived comprising of noble gases, iodine and aerosol. The JRODOS computational software for off-site nuclear emergency management has been utilized to estimate the dose results from the LOCA-initiated source term that is released in its entirety from the reactor stack at ambient temperature. The Local Scale Model Chain in conjunction with the DIPCOT atmospheric dispersion model that is embedded in JRODOS have been used with proper parameterization of the calculation settings. Five weather scenarios have been selected as representative of typical meteorological conditions at the reactor site. The scenarios have been assessed with the use of the Weather Research and Forecast model. Total effective, skin, thyroid, lung and inhalation doses downwind of the reactor building and up to a distance of 10 km have been calculated for each weather scenario and are presented. The total effective gamma dose rate at a fixed distance from the reactor building has been assessed. The radiological consequences of the dose results are discussed.

A source term estimation method for a nuclear accident using atmospheric dispersion models

2015 ◽  
Vol 58 (1/2) ◽  
pp. 39 ◽  
Author(s):  
Minsik Kim ◽  
Ryohji Ohba ◽  
Masamichi Oura ◽  
Shinsuke Kato ◽  
Masayuki Takigawa ◽  
...  
Keyword(s):  
Source Term ◽  
Atmospheric Dispersion ◽  
Estimation Method ◽  
Nuclear Accident ◽  
Dispersion Models ◽  
Atmospheric Dispersion Models ◽  
Source Term Estimation

scholarly journals Source Term Derivation and Radioactive Release Evaluation for JRTR Research Reactor under Severe Accident

2020 ◽  
Vol 2020 ◽  
pp. 1-9 ◽  
Author(s):  
Ned Xoubi
Keyword(s):  
Research Reactor ◽  
Source Term ◽  
Atmospheric Dispersion ◽  
Reactor Core ◽  
Fission Products ◽  
Severe Accident ◽  
Safety Standards ◽  
Gaussian Plume ◽  
Public Exposure ◽  
Radioactive Release

The source term for the JRTR research reactor is derived under an assumed hypothetical severe accident resulting in generation of the most severe consequences. The reactor core is modeled based on the reactor technical design specifications, and the fission products inventory is calculated by using the SCALE/TRITON depletion sequence to perform burnup and decay analyses via coupling the NEWT 2-D transport lattice code to the ORIGEN-S fuel depletion code. Fifty radioisotopes contributed to the evaluation, resulting in a source term of 3.7 × 1014 Bq. Atmospheric dispersion was evaluated using the Gaussian plume model via the HOTSPOT code. The plume centerline total effective dose (TED) was found to exceed the IAEA limits for occupational exposure of 0.02 Sv; the results showed that the maximum dose is 200 Sv within 200 m from the reactor, under all the weather stability classes, after which it starts to decrease with distance, reaching 0.1 Sv at 1 km from the reactor. The radiation dose plume centerlines continue to the exceed international basic safety standards annual limit of 1 mSv for public exposure, up to 80 km from the reactor.

scholarly journals Modeling of atmospheric dispersion with dry deposition: an application on a research reactor

2014 ◽  
Vol 29 (3) ◽  
pp. 331-337 ◽  
Author(s):  
Khaled S. M. Essa ◽  
Soad M. Etman ◽  
Maha S. El-Otaify
Keyword(s):  
Analytical Solution ◽  
Dry Deposition ◽  
Research Reactor ◽  
Atmospheric Dispersion ◽  
Three Dimensional ◽  
Eddy Diffusivity ◽  
Gaussian Shape ◽  
Statistical Measures ◽  
Analytical Formulae ◽  
Using Data

An analytical solution of the three dimensional advection-diffusion equations has been formulated to simulate the dispersion of pollutants in the planetary boundary layer. The solution is based on the assumption that the concentration distribution of pollutants in the crosswind direction has a Gaussian shape and the wind speed is constant. The analytical solution has been obtained in two cases where, the vertical eddy diffusivity is taken to be dependent on: (a) the downwind distance x only and (b) the vertical height z only. The dry deposition of the diffusing particles on the ground is taken into account throughout the boundary conditions. The resulting analytical formulae have been applied to calculate the concentration of I-131 using data collected from the experiments conducted to collect air samples around the Research Reactor. Statistical measures are utilized in the comparison between the predicted and observed concentrations. The results are discussed and presented in tables and illustrative figures.

scholarly journals Detailed source term estimation of the atmospheric release for the Fukushima Daiichi Nuclear Power Station accident by coupling simulations of atmospheric dispersion model with improved deposition scheme and oceanic dispersion model

2014 ◽  
Vol 14 (10) ◽  
pp. 14725-14832 ◽  
Author(s):  
G. Katata ◽  
M. Chino ◽  
T. Kobayashi ◽  
H. Terada ◽  
M. Ota ◽  
...  
Keyword(s):  
Nuclear Power Station ◽  
Nuclear Power ◽  
Source Term ◽  
Dispersion Model ◽  
Atmospheric Dispersion ◽  
Cloud Microphysics ◽  
Air Concentration ◽  
Power Station ◽  
Surface Deposition ◽  
Source Term Estimation

Abstract. Temporal variations in the amount of radionuclides released into the atmosphere during the Fukushima Dai-ichi Nuclear Power Station (FNPS1) accident and their atmospheric and marine dispersion are essential to evaluate the environmental impacts and resultant radiological doses to the public. In this paper, we estimate a detailed time trend of atmospheric releases during the accident by combining environmental monitoring data with atmospheric model simulations from WSPEEDI-II (Worldwide version of System for Prediction of Environmental Emergency Dose Information), and simulations from the oceanic dispersion model SEA-GEARN-FDM, both developed by the authors. A sophisticated deposition scheme, which deals with dry and fogwater depositions, cloud condensation nuclei (CCN) activation and subsequent wet scavenging due to mixed-phase cloud microphysics (in-cloud scavenging) for radioactive iodine gas (I2 and CH3I) and other particles (CsI, Cs, and Te), was incorporated into WSPEEDI-II to improve the surface deposition calculations. The fallout to the ocean surface calculated by WSPEEDI-II was used as input data for the SEA-GEARN-FDM calculations. Reverse and inverse source-term estimation methods based on coupling the simulations from both models was adopted using air dose rates and concentrations, and sea surface concentrations. The results revealed that the major releases of radionuclides due to FNPS1 accident occurred in the following periods during March 2011: the afternoon of 12 March due to the wet venting and hydrogen explosion at Unit 1, the morning of 13 March after the venting event at Unit 3, midnight of 14 March when the SRV (Safely Relief Valve) at Unit 2 was opened three times, the morning and night of 15 March, and the morning of 16 March. According to the simulation results, the highest radioactive contamination areas around FNPS1 were created from 15 to 16 March by complicated interactions among rainfall, plume movements, and the temporal variation of release rates associated with reactor pressure changes in Units 2 and 3. The modified WSPEEDI-II simulation using the new source term reproduced local and regional patterns of cumulative surface deposition of total 131I and 137Cs and air dose rate obtained by airborne surveys. The new source term was also tested using three atmospheric dispersion models (MLDP0, HYSPLIT, and NAME) for regional and global calculations and showed good agreement between calculated and observed air concentration and surface deposition of 137Cs in East Japan. Moreover, HYSPLIT model using the new source term also reproduced the plume arrivals at several countries abroad showing a good correlation with measured air concentration data. A large part of deposition pattern of total 131I and 137Cs in East Japan was explained by in-cloud particulate scavenging. However, for the regional scale contaminated areas, there were large uncertainties due to the overestimation of rainfall amounts and the underestimation of fogwater and drizzle depositions. The computations showed that approximately 27% of 137Cs discharged from FNPS1 deposited to the land in East Japan, mostly in forest areas.

Sign in / Sign up

Export Citation Format

Share Document