Attempts to curb the accumulation of radioactive groundwater at the crippled Fukushima Daiichi nuclear power plant are not proving effective, as groundwater continues to enter radioactive buildings.

Officials from the Tokyo Electric Power Company (TEPCO), which is in charge of the clean-up operation, said that there has been little change in the levels of contaminated water in the effected buildings since the launch of the so-called underground bypass operation in May, according to the Japanese state broadcaster NHK.

The officials said that on August 17 water levels in three wells were down by just 10 centimeters and 20-30 centimeters lower than when they first started taking measurements.

Engineers are trying to reduce the 400 tons of water flowing through the Fukushima buildings every day to 300 tons and to do this they need to lower the level of water in the wells by between several tens of centimeters and a meter.

Scientists believe that their failure to secure a drop in water levels is due to the slow movement of groundwater and the effect of rain on the contaminated water.

They expect the operation may take several more months before any significant effects are seen.

Equipment failure

In a separate setback for the crippled plant a 400 kilogram piece of machinery fell into a nuclear fuel pool at the crippled number 3 reactor.

The incident occurred on Friday when the operating console of a machine to handle spent nuclear fuel slipped loose and fell into a pool containing spent fuel rods.

The operation was being carried out remotely in an attempt to try and remove radioactive debris from the fuel pool, which contains 566 fuel rods, most of them spent.

“The operation was being remotely controlled and there were no injuries caused to workers,” a TEPCO official said.

They stressed that radioactivity readings at the stricken pool remained unchanged at 3.2 millisieverts per hour.

The meltdown at Fukushima occurred after an earthquake and huge tsunami crippled the reactor’s cooling systems. It is the worst nuclear disaster since the Chernobyl accident in 1986.

Just hours after Friday’s incident a 5.0 magnitude earthquake hit off the Fukushima coast but there was chance of a tsunami and no reports of any damage caused.

Japan lies on a tectonic fault line and is prone to frequent earthquakes.