Fukushima watch 2011-04-06

Tepco is now discussing installing a new cooling system in units 1, 2 and 3 of wrecked nuclear power station Fukushima 1 (Fukushima Daiichi), according to a report in Sankei Shimbun. Fresh water will be circulated around the reactor core using new electric pumps running on grid power and cooled in a new heat exchanger using sea water. Two of the five pipes leading into the reactor will be used for that purpose. The heat exchanger and pumps will be located further from the reactor building, exposing technicians to less radioactivity then inside the existing turbine hall. The company expects to be able to get this system working within about one month.

If the plan is successfully implemented, it would be a big step towards regaining control over the ruined reactors. Reestablishing some working cooling circuit is necessary to avoid having to entomb the reactor buildings in concrete, which would forever prevent a removal of the highly radioactive core from the tsunami-exposed site at the Northeast Japanese coast line.

Water leak plugged

The company also reports to have stopped the highly radiaocative water leaks at unit 2 using water glass (a watery solution of sodium silicate). Two previous efforts involving concrete and a water absorbent polymer had failed.

Meanwhile a “megafloat” previously used as a floating island for anglers is being converted at a shipyard in Yokohama for use as a water storage tank and will be towed to Fukushima around April 16. The 146 m long and 46 m wide vessel will be able to hold up to 10,000,000 liters of contaminated water from the reactor site.

Fear of hydrogen explosions

Tepco is currently injecting nitrogen gas into the unit 1 reactor building to dilute a potential buildup of hydrogen gas from overheated fuel elements. It is also considering nitrogen injections into units 2 and 3.

As it is suspected that hydrogen gas is accumulated inside reactor containment vessel, we are considering injection of nitrogen gas inside the vessel.
(Tepco press release)

Hydrogen explosions were responsible for severe damage to units 1, 3 and 4 in the first days after the cooling systems failed. The explosions occurred when gas had to be vented from inside the containment after pressure increased to twice the design limit of the containment vessel. Other Boiling Water Reactors (BWRs) based on GE designs had been retrofitted during the 1980s with hydrogen burners that ignite leaked hydrogen before it has time to accumulate and mix with air in large quantities, but Tepco reportedly considered this retrofit an unnecessary expense.

Fukushima killed “oru denka”

Tepco announced halting its commercial push for “oru denka” (Japanese: オール電化, “all electric power”) households. Sales of “orudenka” goods such as heat pumps will be suspended. Until right before the earthquake and loss of 10,000 Megawatts of electric generation capacity in Fukushima and elsewhere, the company had been luring consumers away from using natural gas or propane for heating, cooking and hot water production and instead relying on Tepco’s now overloaded grid for all domestic power needs. The “eco cute” heat pumps previously sold by Tepco now compete for scarce power while Tepco has to struggle to bring replacement capacity online as quickly as possible to end rolling blackouts that are badly hitting the economy and are set to continue until the end of April. Depending on how quickly alternative power sources can be brought online, more severe power cuts are possible in the summer, the usual peak time for power load when most of Japan switches on air conditioners to escape near tropical humid heat. This summer may be the first in decades without widespread availability of air conditioning in Japan.

Sales of “orudenka” equipment is continuing at Kansai Electric Power Company and Chubu Electric Power Company, two companies not affected by the quake, but the latter has suspended TV advertising for the products.

Tepco has a near monopoly for electricity in Eastern Japan. It can import a maximum of 600 MW through an undersea cable from Hokkaido and a maximum of 1000 MW from Western Japan via DC couplings (Western Japan uses 60 Hz AC vs 50 Hz in Eastern Japan, so it takes more than simple lines and transformers to exchange power between those two grids). Until now this limited exchange of power had worked to Tepco’s advantage, as it kept out competition from suppliers in Western Japan, but Tepco’s customers are now paying the price for it, quite literally, as Tepco is raising their prices to encourage power savings.

Tepco will urgently have to import and start up gas turbines to replace lost capacity. GE in the US has announced it will ship gas turbines to Japan. So far restrictions on power usage are expected to last until summer 2012 in the world’s third biggest economy.

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