ZAPORIZHIA | SPECIAL REPORT


Above: The station has suffered several shelling attacks, with missiles and mines hitting buildings


plant. While the Zaporizhia plant has had its own storage facility since the early 2000s, the three other plants had previously transported spent fuel to Russia with an obligation to eventually receive the radioactive waste back after reprocessing. This project to store the spent fuel at the Chornobyl (along with the VVER-440 fuel) cut off the last Russian-Ukrainian nuclear links.


ZNPP two years on The Zaporizhia nuclear power station was captured by Russian troops on 4 March, 2022, with shelling of the site and important electrical equipment. No significant damage to the units was registered. Before the war, all six units were in operation but half a year later, in September 2022, the last two operating units were shut down. Since then – for almost a year and a half – all reactors


have remained shut down. Russia cannot supply electricity to its territory and does not want to supply it to the territory of Ukraine. Instead, electricity from the Ukrainian grid is used to maintain one unit (earlier two units) in the hot shutdown state. All other units are now in the cold shutdown state. Cold shutdown relates to a fuelled reactor with the


following parameters of the sealed and filled primary circuit – temperature up to 70°C, pressure up to 35 kg/cm2


. The


core is being cooled through the outage cooling system. It’s a three-train safety system with flow up to 800 m3 hour and maximum pressure of 23 kg/cm2


/ . The heat sink is


the sprinkler ponds located on the station territory. During power generation, this safety system is designed for the emergency injection of a low-pressure boric acid solution. Hot shutdown relates to a fuelled reactor and nominal


parameters of the primary circuit – temperature more 260°C and pressure 160 kg/cm2


. The main circulation pumps are in


operation. The heat of the core and the pumps is removed by the secondary circuit that needs the operation of the main turbine systems including the feed water, steam, condensate systems and circulation pumps. In 2023, the State Nuclear Regulatory Inspectorate of


Ukraine issued an order to maintain all the plant units in a cold shutdown state. However, in reality this is a hollow regulation as Energoatom can’t access the site to meet this requirement.


The official Russian explanation for keeping one of the units in the hot state is that it is necessary to produce low parameter steam for the plant water treatment facilities and to heat the town. The town is 6 km from the plant and heat supply from the operating units was normal although using pumps consuming electricity from the grid is an unusual operating mode. Furthermore, a number of movable heating installations


were delivered to the town by Russia and connected to houses during the first winter of the war. Several mobile steam generating installations were also delivered to the station but it still keeps one power unit in the hot state consuming around the same amount of electricity as an operating unit – up to 50 MWe. Spent fuel pools are located at every unit and form a


common space with the reactor during refuelling. Their three-train cooling system is always in operation, in any reactor state, and uses the same cooling water as the reactor cooling system. The plant turbine cooling pond (about 11 km2


) is


separated from the Dnipro River and now is not used due to the plant shutdown. Following the destruction of the Kakhovskaya HPP dam in June 2023 – the Kakhovka water reservoir (52 km3


) emptied and the plant lost the ability to


fill the cooling pond. However, while that is not currently a problem as the plant is not in operation, possible damage to the cooling pond dam could lead to loss of the water and with it the opportunity to make up the safety system sprinkler ponds. Nonetheless, the cooling pond dam proved to be reliable – no leaks were detected, evaporation is minor and its level has been stable for months. The plant drilled several wells on the site and reported on its ability to make up the safety sprinkler ponds. Ukrainian experts reported that this drilling and pumping of the water can impact the site’s ground stability, especially given that some units had problems with inclination in the past. Evaporation from the sprinkler ponds is insignificant,


especially in winter. But the main mitigating factor is a long, almost 1.5-year, shutdown of all reactors therefore having low decay heat of less than 1 MWt per reactor. It’s worth noting another nuclear provision located at the plant – the spent nuclear fuel dry storage facility holding


www.neimagazine.com | March 2024 | 23


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