Reading 21-23

WHAT HAPPENS IN A MELTDOWN? 
What is the current situation with Japan’s nuclear crisis? How does a nuclear reactor work, what is going wrong with the reactors in Japan and what is a meltdown? Read the article below and explain to your teacher how a reactor works and what the situation in Japan is.

New York Times
March 2011
How a Reactor Shuts Down and What Happens in a Meltdown
Inside a nuclear reactor, fuel rods are tubes made of zirconium alloy containing uranium fuel pellets. These rods are immersed in water, and heat generated by the nuclear reaction inside the rods turns the water into steam, which drives turbines to make electricity.
In a shutdown, control rods can be placed between the
fuel rods to stop the nuclear reaction. After the earthquake near Japan, control rods deployed correctly.
Even though the reaction stops, fuel rods continue to give off enormous amounts of heat. To keep the rods from getting too hot, they must be kept submerged in water.
In Japan, there was no electricity to run the cooling system. Operators added water, intending to vent the steam and replace the water as it evaporated. But the water began boiling away faster than they could replace it. The rods were exposed to air, heating
up quickly. As temperatures spiked, the zirconium casing cracked, releasing radioactive gases and hydrogen – probably the cause of the first explosion. It is not known if any of the uranium fuel has melted.
In a full meltdown, fuel pellets would drop to the bottom of the reactor vessel; they might burn through it. An outer containment vessel with steel and concrete walls may or may not hold the melted fuel and prevent it from escaping the reactor building. Worst case: Molten fuel breaches all structures and releases enormous amounts of radioactive material.

Radiation exposure levels are worsening in Japan. But how much radiation is too much and what are we all exposed to? Look at these figures and calculate how much radiation you are exposed to:

Radiation dosages are measured in sieverts. These figures are millisieverts (mSv).
6,000 Typical dosage recorded in those Chernobyl workers who died within a month.
5,000 Single dose which would kill half of those exposed to it within a month.
1,000 Single dose which could cause radiation sickness, nausea, but not death.
400 Maximum radiation levels recorded at the Fukushima plant on March 14 per hour.
350 Exposure of Chernobyl residents who were relocated.
100 Recommended limit for radiation workers every five years.
10 Dose in full-body CT scan.
9 Airline crew NYC-Tokyo polar route, annual.
2 Natural radiation we’re all exposed to, per year.
0.1 Chest x-ray. 0.01 Dental x-ray.

Discussion How safe do you think nuclear power is? Do you have nuclear reactors in your country? If so, is your government taking any specific action in light of the Japanese crisis? Are you for or against nuclear power? What advice is your country giving its citizens who are currently in Japan? Do you think Japan is dealing with the crisis well?

Language focus Look at these extracts from the article:
‘How a Reactor Shuts Down...’
‘In a shutdown, control rods can be placed between the fuel rods...’
From these extracts you can see how you make the noun shutdown from the phrasal verb shut down. There are a number of compound nouns formed this way. Complete the gaps in these sentences using compound nouns formed from the verbs and prepositions below.

back break clear get feed hand hide set shoot take
away away back back out out out out up up

1 After the ________ the bank robbers made a quick _________ and headed for their _________.
2 After their ____________ Rachel and Steve never spoke again.
3 This place is full of rubbish, we need to have a good ____________.
4 The students completed the ______________ that their teacher had given them.
5 After a number of ______________ they eventually felt that they were making progress.
6 I don’t want to cook tonight, let’s get a _________________.
7 Can you make a ______________ of all this work I’ve done on the computer?
8 The supermarket asked its customers for ____________ on its new products.

Practice Ask your teacher questions using four compound nouns you would like to learn.

Vocabulary focus Find these words in the article and explain their meanings to your teacher:

alloy fuel deploy submerge spike crack breach

Now match the words to these definitions:
_______________ to break without complete separation of parts
_______________ a metal made by combining two or more metallic elements
_______________ to break through a wall or barrier
_______________ to put below the surface of water
_______________ to come into use
_______________ an energy source for engines, power plants or reactors
_______________ to rise or increase sharply

Practice Write sentences with four of the words you would like to learn.