Finland's Fortum has received "a significant additional order" from US-based EnergySolutions for its Nures ion exchange materials to treat radioactive water at the Japan's Fukushima-Daiichi nuclear power plant.

Fortum's ion exchange materials have been used in the advanced liquid processing system (Alps) at Fukushima-Daiichi to purify radioactive waters for the past three years. The order is one of Fortum's largest deliveries of ion exchange materials to date, a statement said. The materials remove radioactive material such as caesium and strontium from water. Nures, which Fortum initially developed for use at its Loviisa nuclear plant, contains extremely selective ion exchange materials to absorb radioactivity. Fortum says its method significantly reduces the need for intermediate and final disposal repository space for radioactive liquids.

Earlier this month, treated groundwater from Fukushima-Daiichi was released into the sea for the first time. Tokyo Electric Power Company (Tepco) conducted the operation by pumping up the treated water from a series of wells in and around reactor and turbine buildings destroyed in the 2011 nuclear accident. Tepco said radiation levels of the water were within government standards. Tepco released some 850t of filtered groundwater - part of the 4000t pumped up last year on a trial basis and stored in tanks after ensuring that radiation levels were below measurable limits. Tritium, which cannot be removed with existing technology, measured 330-600 becquerels per litre, well below the legally allowable limit of 1500 becquerels, Tepco said.