Fukushima 1 Nuclear Accident Day 18, 19, 20

Monday, 28 March

High levels of radiation from contaminated water hindered work on restoring the cooling pumps and other powered systems to reactors 1-4. The Japanese Nuclear Safety Commission reported that it assumed melted fuel rods in Unit 2 released radioactive substances into cooling water which subsequently leaked out through an unknown route to the Unit 2 turbine building basement.

In hopes of reducing the amount of water leaking, TEPCO reduced the amount of water pumped into Reactor 2 from 16 tons per hour to 7 tons per hour, despite the priority of cooling the reactor core. Confirming concerns, the temperature in the reactor raised by 20°C. Highly radioactive water was also found in three "trenches" (tunnels that house electrical wires from the turbines) which stretch toward, but do not connect to, the sea. Water levels in trenches of Units 2 and 3 were 1m below the level at which they would overflow to the sea, while the Unit 1 trench was 10cm from overflowing. TEPCO reported they used sandbags and concrete to prevent an overflow at the opening of the tunnel.

TEPCO confirmed finding low levels of plutonium in five samples from 21 March and 22 March, concluding that "two samples out of five may be the direct result of the recent incident."

Tuesday, 29 March

Unit 1 water injection is transfered from fire engine pumping to an emergency pump. Unit 4 control room power is restored, the final control room to receive power. Unit 2 and 3 water injection changes from salt water to freshwater. Radiation reaches the United Kingdom, with very low levels of radioactive iodine detected in Glasgow and Oxfordshire, although there is no evidence that this iodine is from Japan.

Wednesday, 30 March

Smoke escaped from the Fukushima II (Dai-ini) nuclear plant. Fukushima II plant is 6 miles from the Fukushima I (Dai-Ichi) facility, and was thought not to be at risk.

At Fukushima I, Japan's Nuclear and Industrial Safety Agency (JNISA) reiterated concerns about a unit 3 breach on 30 March. NHK World reported the JNISA's concerns as "air may be leaking," very probably through "weakened valves, pipes and openings under the reactors where the control rods are inserted," but that "there is no indication of large cracks or holes in the reactor vessels." Plans were announced to spray debris at the Fukushima plant with a water-soluble resin to prevent further spread of radioactivity. The concentration of 131
I in seawater, 330 m south of the discharge canal of units 1 to 4 at 13:55, March 29th, 2011, was 130,000 Bq/l or 3,355 times the regulatory limit (the highest so far). The concentration of 134
Cs was 520 times the regulatory limit, while 137
Cs was 350 times the limit.

Nuclide	Concentration (Bq/cm3)	Regulatory limit (Bq/cm3)	Concentration / Regulatory Limit
99m Tc	1.6×10−1	4.0×101	.04
131 I	1.3×102	4.0×10−2	3250
134 Cs	3.1×101	6.0×10−2	517
136 Cs	2.8×100	3.0×10−1	9.3
137 Cs	3.2×101	9.0×10−2	356
140 Ba	5.0×100	3.0×10−1	17
140 La	2.5×100	4.0×10−1	6.3

In Primorsky Krai, Russia, the Head of the Maritime Administration on Hydrometeorology and Environmental Monitoring reported trace amounts of radioactive iodine-131 detected in air samples taken from 26 March to 29 March.