The operator of the Fukushima No. 1 nuclear power plant conducted a test Monday temporarily halting the water being injected into one of the reactors that suffered a core meltdown in the wake of the 2011 accident.

Through the test, which was the first of its kind, Tokyo Electric Power Company Holdings Inc. plans to obtain data on how the temperature inside the No. 2 reactor could rise in the event of an emergency, and use that information to update its planned response.

More than eight years since the start of what has become one of the world’s worst nuclear crises, Tepco continues to pour water into the Nos. 1 to 3 reactors in order to keep the melted fuel debris inside them cool.

At 10:40 a.m. Monday, Tepco completely halted the water injection into the No. 2 unit, which usually receives around 3 tons of coolant per hour.

The temperature at the bottom of the reactor pressure vessel, a container that is supposed to hold the fuel, stood at about 24.5 degrees Celsius. Tepco expected the reading to rise by up to 4 C following the seven-hour test.

Hit by a magnitude 9.0 earthquake and ensuing tsunami on March 11, 2011, the Fukushima nuclear complex lost nearly all its power sources and, consequently, the ability to cool the reactors and spent fuel pools at the Nos. 1 to 4 units.

The condition of the reactors is now kept relatively stable through recovery efforts, but a massive amount of contaminated water has accumulated at the plant as a result.