Application of Regional Environmental Code Harp in the Field of Off-site Consequence Assessment

The environmental code HARP (HAzardous Radioactivity Propagation) estimates consequences of accidental radioactivity releases from a nuclear facility and on basis of simulation of dispersion in atmosphere, deposition of radionuclides on the ground and further propagation through the food chains towards human body. Classical Gaussian approach in the form of hybrid puff-plume segmented model SGPM is introduced for simulation of pollution dissemination in the atmosphere. The ingestion pathway is modeled dynamically. The system architecture consists of the inner kernel designated for deterministic calculations and outer probabilistic shell, which ensures application of probabilistic approach in the consequence assessment. Propagation of uncertainties through the model towards the output values of interest is realized through the multiple recalling procedure of the inner kernel, which is optimized for such intensive Monte Carlo (MC) computations. The HARP code is primarily designed for application of advanced statistical data assimilation techniques based on sequential MC methods (SMCM) allowing an improvement of model predictions using real measurements incoming from terrain. In this paper we shall demonstrate two additional specific applications of the HARP code based on the repeated sampling. Firstly, a partial PSA-Level3 study of ecological risk assessment is accomplished taking into account variability of meteorological inputs represented by historical long sequences of archived values (for each hour in the years 2008 and 2009). Output radiological quantities are then processed statistically. Secondly, a long term release of radioactive material is simulated through the superposition of a large number of one-hour fractional release rates. The procedure is applied on annual radioactivity releases from a nuclear power plant (NPP) during its routine normal operation when each partial hourly release is driven by the real meteorology archived at that time.