Nuclear Energy Institute Reports Explosion at Fukushima Daiichi Unit 3 Reactor

Washington, D.C.–(ENEWSPF)–March 13, 2011.  At 11:01 pm EDT, Tokyo Electric Power Co. confirmed that an explosion occurred at Fukushima Daiichi Unit 3. The reactor’s building wall and ceiling were blown off. TEPCO officials said it was likely a hydrogen explosion as occurred at Unit 1 Friday, but did not have enough information to confirm this.


Fukushima Daiichi

The hydrogen explosion on March 11 between the primary containment vessel and secondary containment building of the reactor did not damage the primary containment vessel or the reactor core.  To control the pressure of the reactor core, Tokyo Electric Power Co. began to inject seawater and boric acid into the primary containment vessels of Unit 1 on March 12 and Unit 3 on March 13.  There is likely some damage to the fuel rods contained in Units 1 and 3. 

At both Units 1 and 3, seawater and boric acid is being injected into the reactor using fire pumps. On Unit 3, a pressure relief valve in the containment structure failed to open, but was restored by connecting an air pressure to the line driving valve operation.

The water level in the reactor vessel of Unit 2 is steady.

Personnel from TEPCO are closely monitoring the status of all three reactors.

The highest recorded radiation level at the Fukushima Daiichi site was 155.7 millirem at 1:52 p.m. EDT on March 13. Radiation levels were reduced to 4.4 millirem by the evening of March 13. The Nuclear Regulatory Commission’s radiation dose limit for the public is 100 millirem per year. 

Japanese government officials acknowledged the potential for partial fuel meltdowns at Fukushima Daiichi Units 1 and 3 reactors, but there is no danger for core explosion, as occurred at the nuclear power station at Chernobyl in 1986. Control rods have been successfully inserted at all of the reactors, thereby ending the chain reaction. The reactor cores at Fukushima Daiichi and Daini power stations are surrounded by steel and concrete containment vessels of 40 to 80 inches thick that are designed to contain radioactive materials.

Fukushima Daini

The Fukushima Daini plants remains in a state of emergency. There is electricity available at all four of the reactors at Fukushima Daini, although there is limited availability of the cooling water pumps at Units 1, 2 and 4. 

TEPCO is working to maintain constant cooling in the primary containment vessels of those reactors. No radioactivity has been recorded outside of the secondary containment buildings at Fukushima Daini, according to TEPCO.

Two other nuclear power plants in the Tohoku region, Onagawa Nuclear Power Station and Tokai Nuclear Power Station, were automatically shut down in response to the earthquake. The four reactors at these plants have functioning cooling systems and are being monitored by plant operators. 

The Rokkasho Reprocessing Plant and accompanying facilities, located far north of the tsunami zone in Rokkasho Town, is operating safely on backup power generation systems. 

Japanese nuclear facilities are designed to withstand powerful seismic events, such as earthquakes. In this earthquake—the strongest recorded over the past 100 years in Japan—the containment structures of Fukushima Daiichi maintained their structural integrity. These facilities were designed to withstand tsunamis within a range of assumed strength; however, the force of the tsunami on March 10 exceeded the assumed range and flooded diesel generators at Fukushima Daiichi power station.  This precipitated the loss of power for the reactor cooling systems.

The automatic shutdown of the 11 operating reactors at the Onagawa Nuclear Power Station, Tokai Nuclear Power Station, Fukushima Daiichi and Daini, represents a loss of 3.5% of electric generation capacity for Japan.