A numerical assessment of the dispersion of dissolved pollutants in the Arabian Gulf associated with the Barakah nuclear power plant

The main goal of this study is to investigate long-term dispersion of quasi-conservative pollutants in the Arabian Gulf, such as anthropogenic radionuclides, associated with regular and potential accidental emissions of those from the recently commissioned Barakah nuclear power plant (BNPP) in the western United Arab Emirates (UAE). In particular, discharge of tritium 3H, which is expected to be present in the cooling water effluent during normal operation of the plant, raises concerns about eventual build-up of tritium and tritiated water plume in the poorly flushed western UAE region. A good understanding of the transport processes in the sea is also essential for contingency planning in case of accidental releases of harmful radionuclides such as Cesium 137Cs, and it provides basis for more comprehensive models of the marine radioactivity. To achieve this goal, a three-dimensional unstructured-grid hydrodynamic and tracer dispersion model of the Arabian Gulf, focusing on the western UAE area, was established using Semi-implicit Cross-scale Hydroscience Integrated System (SCHISM). The model was validated against water level, current and temperature data collected in the UAE waters during 2017-2018. The horizontal resolution of the numerical mesh of this model varied from approximately 4 km in the Sea of Oman to 0.1 km near Barakah to properly account for the effect of numerous small islands, narrow straits between them, and other fine-scale coastal features on the hydrodynamic. Two types of scenarios were considered: (1) direct continuous release of a tracer dissolved in the BNPP's heated effluent, and (2) offshore fallouts from the atmosphere onto the water surface. The simulations were conducted over the period of 2 years. Direct continuous tracer discharge was found to cause a notable accumulation of it in the Southern Shallows region, especially Barakah - Sir Bani Yas - Dalma - Yasat Islands zone, where the volume-averaged concentration converged to approximately 7.4% of the excess concentration of the tracer in the BNPP effluent, with the Gulf-averaged saturation concentration projected at approximately 0.37%. The quasi-half-saturation states for these two regions were reached in approximately 0.4 and 1.8 years, respectively. A pollutant plume resultant from an atmospheric fallout generally tends to move eastward along the UAE coast, with the separation occurring in the western approaches of the Strait of Hormuz, between Dubai and Ras Al Khaimah, where a denser near-bed portion continues sinking down and then exits into the Sea of Oman, while a near-surface portion is entrained into the general counterclockwise circulation in the Gulf, and it is carried along the Iranian coast to the upper northwestern Gulf. After the period of 2 years, 60-70% of the total initial tracer load is estimated to be washed out from the Gulf. Despite relatively low probability of the occurrence of such wind conditions, which could result in radionuclide fallouts north of Dalma Island, a notably faster spread of contaminated waters, with the estimated 5-6 weeks for a peak concentration to reach Abu Dhabi City in the studied case, would make emergency response more challenging.