Editor's Note: John Boyd is an IEEE Spectrum contributor reporting from Kawasaki, Japan. This is part of IEEE Spectrum's ongoing coverage of Japan's earthquake and nuclear emergency. For more details on how Fukushima Dai-1's nuclear reactors work and what has gone wrong so far, see our explainer and our timeline.
One week after the devastating 9.0 magnitude earthquake hit northeast Japan, authorities further raised their efforts to get Japan’s damaged Fukushima Dai-1 nuclear power plant under control today. Thirty squads of fire fighters from Tokyo arrived in Iwaki, a small town south of the plant, and prepared to help the country’s Self-Defense Force (SDF), which has been discharging water into the critical reactor No. 3 building. At the same time Tokyo Electric Power Co. (TEPCO) repair crews were working to bringing power to the site from grid lines despite dangerous radiation conditions.
Minister of Defense Toshimi Kitazawa told reporters that there would be “no helicopter water drops conducted today," which suggests yesterday’s four water drops over the reactors were ineffective or perhaps too dangerous to continue with for a second day. But he said that SDF groups would resume their efforts from yesterday evening and use water cannon trucks to jet water into the No. 3 reactor building. The aim is to refill the spent fuel storage pool, which contains hundreds of spent fuel rods.
The pool has been losing water through evaporation. White steam was seen billowing from the building Wednesday morning and continued to be emitted Thursday and Friday, indicating that the water was boiling away. Parts of the fuel rods may therefore be exposed to air. That exposure would cause the still-radioactive spent fuel to heat further and could cause it to begin melting, which would create a major source of radiation leakage. The temperatures in the storage pools of No. 4, 5 and 6 have also reportedly been heating up, but according to TEPCO and Japanese officials they have not so far become as critical as the situation at No. 3.
(Contradictory reports continue to come from U.S. nuclear engineers and officials regarding the No. 4 building's storage pools. Yesterday the head of the U.S. Nuclear Regulatory Commission declared that pool empty of water, and today the Los Angeles Times reported that the wall or floor of the 45-foot-deep pool may have a crack or breach. If true, that would make it more difficult to keep water over the spent fuel rods in the No. 4 pool.)
Meanwhile, at a press conference around 10 a.m. Friday TEPCO officials said that repair crews had laid a 930-meter cable from the electricity grid and were making preparations to connect it to a temporary distribution panel. From that panel they would connect power to the No. 2 reactor building transformer and later the No. 1 reactor building transformer. Since last Friday's earthquake and tsunami, the power plant has been relying on backup generators and batteries.
More than 320 TEPCO workers are now battling to stabilize the plant in various ways, including some 50 workers who are working close to the plant, apparently on a daily basis.
In some ways, experts say, the No. 2 reactor to be in a more critical condition than the troubled storage pool of the No. 3 reactor. An earlier explosion in the No. 2 reactor building is believed to have caused damage to the reactor’s suppression pool. The suppression pool (also called the torus) is connected to the primary containment vessel, the structure that protects the chamber where nuclear fission takes place. TEPCO has reported that the pressure inside the reactor had dropped, suggesting that the primary containment vessel may have been damaged by the accident at the suppression pool. That could mean that radioactive material is leaking from the primary containment vessel.
But experts point out that there's another line of protection--the secondary containment building, which does not appear to be damaged. “The situation with No. 2 is not good either, but the building has a roof,” Kazuaki Matsui, executive managing director of the Institute of Applied Energy, an independent organization in Tokyo, told Spectrum. “There may be a hole or damage in the suppression chamber and there could be some radiation leakage from the water there. But as long as it stays in the building, then it can be fixed later.”
This is not the case with the No. 3 building, which is badly damaged. “No. 1 and No. 3 (buildings) don’t have roofs,” says Matsui. “So if (exposed spent fuel) emits radioactive materials, then this is a more tense situation.”
NHK, Japan’s national broadcaster, showed live footage of water being jetted into the No. 3 building starting from 1:55 p.m local time on Friday. The footage was taken from a helicopter positioned over 30 kilometers west of the plant looking towards the Pacific Ocean. When the operation began, white steam almost immediately billowed upwards from the building, indicating that water was entering the troubled storage pool.
While the vehicles weren’t observable, it was later confirmed that the SDF mounted the operation. The plan was to shoot 45 metric tons of water into the building using six fire trucks. This was in addition to the 27 metric tons the SDF injected into the same building yesterday evening. One truck at a time was used and the operation was temporally halted after three trucks discharged their loads, then it resumed again later for total of six discharges. NHK later reported that TEPCO workers also took part using a seventh fire truck borrowed from the U.S. military.
Yukio Edano, Japan's chief cabinet secretary, said in a later press conference he was sure the operation had achieved some success because “of the steam coming from the building afterwards.”
At 5:30 p.m. local time five Tokyo firefighting trucks left their base in Iwaki and began making their way to the plant, on a mission to inject water into the No. 1 building. As of 8:30 p.m. no word had come whether or not they had begun the operation. NHK reported that TEPCO repair crews were being hampered by radiation close to plant, and said the company was now hoping to bring power to the No. 2 reactor building and get cooling systems operating again by Saturday.
Prime Minister Naoto Kan addressed the nation in an evening broadcast and commented on the Fukushima plant, saying, “The situation surrounding the accident is still very grave. To overcome this crisis, the police, fire fighters, Self-Defense forces and other groups are all working together, putting their lives on the line in an attempt to solve the situation.”