Experimental investigation on 3H washout by rainfall at Kakrapar Atomic Power Station, Gujarat, India

Investigation on tritium (3H) washout process in a tropical region at Kakrapar Atomic Power Station (KAPS), Gujarat, India was carried out. 3H concentration in air as well as that in rainwater is estimated near KAPS Site having Pressurized Heavy Water Reactors (PHWRs) operational. Samples were collected covering the four rainy seasons from 2016 to 2019. The corresponding meteorological parameters of relative humidity, ambient temperature, wind speed, wind direction, and atmospheric stability were measured. The rain spectral characteristics such as raindrop diameter, fall velocity, liquid water content (LWC) in raindrops and average rain rate are also studied. Site-specific wet deposition rate (Bq m-2 s-1) and washout coefficient for 3H (s-1) is observed to be in the range of 1.4E-05 to 4.8E-01 (Geometric Mean = 5.3E-03) and 1.1E-07 to 3.6E-02 (Geometric Mean = 4.1E-05) respectively. Significant and positive correlation was observed between average rain rate and washout coefficient (R2 = 0.73). Significant and negative correlation was observed between raindrop diameter of different rain events and 3H activity in rainwater (R2 = 0.70).