- SPEEDI (System for Prediction of Environmeental Emergency Dose Information)
- PHYSIC (Prognostic Hydrostatic model Including turbulence Closure model)
- PRWDA (Particle Random Walk Dispersion in Atmospheric model)
SPEEDI predicts dose distributions resulting from accidental discharge of redioactivities from nuclear plants. Parallelization of SPEEDI has been started in 1995, under the contract between Japan Science Technology Agency and RIST.
This model consists of five prognostic equations; The momentum equations of horizontal components with the so-called Boussinesq and hydrostatic assumptions, the conservation of heat, turbulence kinetic energy, and turbulence length scale. Z* coordinate system is used because it allows the existence of complex terrain. In pallelization, the whole three-dimensional area to be considered is divided into smaller regions, each of which is assigned to one of PEs (Processor Elements) and each PE calculates wind field prognostically within the assigned region.
The particle dispersion model in PRWDA is for atmospheric dispersion. PRWDA employs a random walk model based on the gradient-transfer theory. Use of marker radioactivity particles for simulation can eliminate numerical diffusion that sometimes appears in different models. Attribute of particles can be specified in additional information, e.g., radioactivity, dose type, travel time, etc. In parallelization, whole radioactive particles are divided into sub groups, each of which is assigned to one of PEs, and each PE calculates diffusion, concentration and dose of the particles within the assigned group. And the algorithm to generate parallel random number is implemented.