In the two months since Japan’s Fukushima Daiichi nuclear power plant was pummeled by a quake and tsunami, no news has generally been good news.
Unfortunately, today, there’s some news.
Tokyo Electric Power Company (TEPCO) announced on Thursday that the damage to fuel rods inside Unit 1′s reactor core is worse than the utility previously thought. Despite the fact that workers at the plant have been pouring tons of water into the reactor since its cooling system was destroyed over two months ago, water levels inside the pressure vessel, where fuel rods are stored, are lower than expected. The low water levels mean that the remaining intact fuel rods are probably fully exposed, and others have already at least partially melted and “slumped” to the bottom of the containment vessel, where they are underwater.
Undamaged, the fuel rods inside the Unit 1 should be 4.5 meters (about 14.7 feet) tall. Previous readings indicated that the water was 1.65 meters below the top of the rods, leaving them partially exposed. But yesterday’s information indicates that water levels are as much as 5 meters below the top of the rods – in other words well below the bottom of the rods. (Here’s a good graphic of the situation inside Unit 1 from the Daily Yomiuri.)
The utility also announced that it had found multiple holes in the bottom of the pressure vessel. Coupled with the low water levels, those holes indicate the contaminated water has been leaking into the outer shell around the fuel storage area, called the containment vessel, and potentially out onto other parts of the site. To keep temperatures down, fresh water has been continuously poured into the spent fuel pools and reactor cores of Units 1, 2 and 3 since the early days of the crisis. (In Unit 4, there is no fuel in the reactor core, but water has been poured into the spent fuel pool. The cooling systems of Units 5 and 6 are both online and they have both been in cold shutdown since March 20.) Containing the large volume of contaminated water has been a problem for weeks and poses an ongoing risk for workers trying to gain access to the reactor buildings to start repairs on the cooling systems.
(Here’s a video of conditions inside the plant shot in late April.)
It’s important to note, however, that the worst has not come to pass, nor do experts believe that it will. In that scenario, all of the rods would have fully melted, collapsed, and burned through the pressure and containment vessels, causing a large radioactive leak outside. But the constant pouring of water onto the rods has prevented that from happening, and the temperatures of 100 to 120 C that TEPCO reports measuring in the pressure vessel of Unit 1 indicate the rods are no longer hot enough to keep melting. According to the Japan Times, TEPCO spokesman Junichi Matsumoto told reporters at a press conference on Thursday: “We’re not sure how much of the fuel rods fell down to the bottom and in what form, but the temperature shows that they are being cooled.”
The new information about water levels in Unit 1, obtained after workers were able to enter the Unit 1 reactor building and adjust water gauges, now has officials worried that water level readings at Units 2 and 3 may also be wrong. It also throws a wrench in TEPCO’s sunny plan of having the crisis at the plant sewn up before the end of the year. And once the utility does achieve cold shutdown in all six reactors, it will face the problem of what to do with the damaged and unstable fuel rods. Whether the company will be able to remove the badly damaged fuel rods from the pressure vessel structures into storage pools, or have to neutralize the rods in situ by pouring cement into the structure, remains to be seen.
Those are some of the problems this new development will create for TEPCO, anyway. What kind of problems will it create for the thousands of people who have lived for years in the shadow of Fukushima, assured repeatedly by the company and the government that it would never affect them? This kind.
