TEPCO finally admits, after confronted with the calculation by Tokyo Shinbun. To no surprise to anyone but TEPCO, the Japanese government, and probably the majority of the Japanese people, the basement walls and floors are likely to have cracked and been damaged during the earthquake.
If this is true, it's good in one sense. Instead of the highly contaminated water in the basements leaking into the groundwater, the groundwater is coming into the basements...
From Tokyo Shinbun (7:06 AM JST 9/20/2011):
福島第一 建屋に地下水大量流入か 収束作業に難題
Large amount of groundwater flowing into the basements at Fukushima I? Obstacle to the work to wind down the accident
東京電力福島第一原発１～４号機の原子炉建屋やタービン建屋地下に、一日数百トンの地下水が流入している可能性のあることが分かった。汚染水処理の 実績などから計算すると、五万トン強まで減っているはずだが、実際には八万トン強も残る。東電も地下水流入の可能性を認めており、地震で建屋地下の壁が損 傷し、流入していることが考えられる。今後の収束作業に影響が出そうだ。
It's been revealed that there is a possibility that several hundred tonnes of groundwater may be flowing into the basements of reactor buildings and turbine buildings in Reactors 1 through 4 at Fukushima I Nuclear Power Plant. The amount of contaminated water should have decreased by now to slightly over 50,000 tonnes, based on the amount of water processed. However, there are still over 80,000 tonnes of highly contaminated water remaining in the basements. TEPCO has admitted to the possibility of groundwater flowing into the basements, whose walls may have been damaged in the earthquake and are letting in the water. This may affect the future work to wind down the accident.
Tokyo Shinbun calculated the hypothetical amount of the remaining contaminated water, based on the data published by TEPCO on the amount of contaminated water transfer and the amount of water injection into the reactors. According to our calculation, about 100,000 tonnes of contaminated water should have been reduced to about 51,600 tonnes by September 13.
However, the latest estimate by TEPCO from the actual water levels in the basements is 81,300 tonnes, leaving 30,000 tonnes or so gap from the calculated amount.
So far, TEPCO has explained that the contaminated water is not decreasing as fast because of the rainwater. Around Fukushima I Nuclear Power Plant, there have been 3 heavy rainfalls since July. Part of the rain may have entered the buildings through the damaged rooftops. However, the contribution of rainwater to the water in the basements is not big enough to explain the 30,000 tonnes difference.
It has been pointed out before that the groundwater may be flowing into the basements through cracks in the basement walls, and now that possibility is even more heightened. We showed the result of our calculation to TEPCO, and they answered "The water may be flowing in in the order of 100 tonnes per day".
If the groundwater is indeed flowing into the basements, the amount of contaminated water to be treated will be further increased, necessitating the decrease of water being injected into the reactors. The work to wind down the accident may be affected in many ways.
I don't know whether TEPCO means "100 tonnes per day per unit" or "100 tonnes per day per each building" or "100 tonnes per day at the plant".
In the latest announcement on the contaminated water processing on September 14, TEPCO is processing about 1,500 tonnes per day.