Re: They are being more assertive now.

Workers Use Coagulant To Stop Fukushima-Daiichi Leak

Unplanned Events & Incidents

6 Apr (NucNet): Workers at the Fukushima-Daiichi nuclear power plant have used 6,000 litres of coagulant to stop a leak from a trench next to the unit 2 inlet point that has been causing highly contaminated water to flow into the sea since 29 March.


Plant owner and operator Tokyo Electric Power Company (Tepco) said today that they used liquid tracer to find the source of the leak in the concrete utility trench and then used the coagulant to seal it. The company said the leak had stopped by 09:30 this morning, Japan time (02:30 central European time).

Additional measures will now be carried out to prevent the discharge of radioactive material from the trench, which holds electric supply cables. One possible measure is to continue the injection of coagulant, Tepco said.

Iodine-131 and Caesium-137 were both detected in water sampled in the trench and in the sea near the water discharge.

The leak was discovered on 2 April when workers detected water releasing a radiation dose rate of more than 1,000 millisieverts per hour in the trench and found a crack about 20 cm wide on the trench’s concrete wall, from where water was thought to be flowing into the sea.

On 2 April, concrete was poured into the trench in an attempt to stop water leaking into the sea, but no significant decrease in leakage was seen. On 3 April, the top of the trench was broken open and polymer was poured into the trench to stop the leak, but this measure was also unsuccessful.

Meanwhile, Tepco has begun discharging into the sea low-level radioactive wastewater stored in sub-drain pits at units 5 and 6 and in a reservoir of the central radioactive waste disposal facility.

Tepco plans to discharge approximately 10,000 tonnes of low-level radioactive water and about 1,500 tonnes of the low-level radioactive subsurface water into the sea.

The discharge is necessary because workers need to use the reservoirs for storing highly radioactive water from the unit 2 turbine building, where radioactive water 100,000 times the normal level in an operating reactor has been found in the turbine building basement. There is a risk that this radioactive water might also flow into the sea.

Tepco said it is concerned that vital equipment needed to secure the safety of the reactors might be submerged if this water is not drained.

The utility is also monitoring an accumulation of hydrogen gas in the primary containment vessel of unit 1 Measures are being taken to avoid a hydrogen explosion similar to the explosion in the primary containment vessel of unit 2.

>>Related reports in the NucNet database (available to subscribers)

Tepco Makes Progress In Bid To Restore External Power (News in Brief No. 77, 23 March 2011)

Japan Update: Work Begins To Remove Contaminated Water (News in Brief No. 82, 27 March 2011)

Tepco Prepares Liquid Glass Injection To Stem Leak (News in Brief No. 91, 5 April 2011)


Source: NucNet
Editor: david.dalton@worldnuclear.org
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