#Fukushima I NPP: Plan C Also Failed in Plugging Reactor 2 Trench... Now What?

Plan D of Course!

But first, recall that Plan A was to install freezing pipes at the head of the trench leading from Reactor 2 turbine building to create an ice plug so that the extremely contaminated water that had been sitting in the trench since the very beginning of the nuclear accident could be pumped out. TEPCO started the work in April this year.

That failed. The ice plug didn't quite form.

Then recall that Plan B was to dump tons (literally) of ice and dry ice in the trench near the freezing pipes to lower the temperature of the water around the freezing pipes so that the ice plug would finally form. Workers dumped ice all day and all night, in the high ambient radiation right at the trench. That was in hot August. Try to freeze the trench with ice in hot August.

That also failed. Dry ice clogged the pipe, and the ice plug didn't quite form, and TEPCO admitted there was water still coming into the trench from the turbine building. The water sitting in the turbine building comes from the reactor building after it cools the molten core somewhere in the building, and it is warm.

So TEPCO came up with Plan C.

What was Plan C? It was to fill the gap between the incomplete ice plug and the turbine building wall with fillers. TEPCO chose the combination of grout and concrete. A plug of ice, grout and concrete was formed. Sort of.

From TEPCO's document uploaded at Nuclear Regulation Authority's site on 11/21/2014, the plug - pink and light green in the diagram is grout (different types), dark green is concrete:

That failed, just as I predicted.

TEPCO finally admitted on November 17 that it was a failure after pumping out some 200 tonnes of this highly contaminated water on November 17 and seeing that the water level in the trench didn't go down as much as they had calculated. The water was still coming in from the turbine building, and the groundwater was probably seeping in.

But not to worry. TEPCO has Plan D, and it has been already approved by Nuclear Regulation Authority.

So what is Plan D? To fill the trench with cement while pumping out the water that gets displaced (in theory) by the cement.

(Do you want to bet whether that is going to fail?)

From Mainichi English (11/18/2014), from the original Japanese article on 11/17/2014:

An effort to stop contaminated water from flowing into a trench at the crippled Fukushima No. 1 Nuclear Power Plant failed to completely halt the flow, announced Tokyo Electric Power Co. (TEPCO), the plant's operator, on Nov. 17.

A TEPCO representative said, "We believe we have not completely stopped the water. Groundwater may also be entering the trench. We will closely analyze the changes in water level in the trench."

TEPCO says that when around 200 tons of contaminated water was removed from the trench, the water level in the trench should have fallen by around 80 centimeters if the point of leakage between the plant's No. 2 reactor turbine building and the trench had been fully sealed. However, the water level only fell by 21 centimeters, so TEPCO determined that the leak must be continuing.

...While the water remains in the trench, TEPCO cannot create a planned underground wall of frozen soil around the No. 1 through 4 reactor buildings to stop water leakages.

And this image from Tokyo Shinbun (11/21/2014):

and reference to Plan D:

トンネルから汚染水を少しずつ抜きながら、水中で薄く広がる特殊なセメントを流し込んでトンネルをふさぐ方法への切り替えを提案する

(TEPCO) will propose (to Nuclear Regulation Authority) a new method of plugging the trench by pouring in the special cement that spread thin and wide in the water while removing the contaminated water in the trench gradually.

Special cement?

TEPCO says in the document (page 9) they submitted to NRA that it will be a mixture of cement, fly ash and underwater-inseparable admixtures (セメント、フライアッシュおよび水中不分離混和剤などの配合調整). They will use the tremie concrete placement method.

(Do you want to bet whether that is going to fail?)

The NRA meeting on November 21, 2014 was funny without participants intending to be funny, from what I read in the tweets by people watching the meeting.

At one point, Commissioner Fuketa exasperatedly asked TEPCO representatives, "So what was the point of trying to freeze the water? Was freezing even necessary at all?"

The answer was no. TEPCO's Shirai admitted (according to the tweet by @jaikoman on 11/21/2014) that there was a talk inside TEPCO that the ice plug was not necessary.

So why did they do it, and why did NRA approve it?

No one knows and no one is held accountable, while workers had to set up freezing pipes, then to pour ice, dry ice, grout, concrete, and to pump this highly contaminated water over the past 8 months in high radiation exposure. TEPCO hasn't disclosed the radiation exposure for the workers.