The Fukushima Daiichi nuclear accident

The Fukushima Daiichi nuclear accidentThe Fukushima Daiichi nuclear accident
The Tohoku earthquake and tsunami that hit Japan on Ma
rch 11, 2011 caused devastating
damage. In this
assignment, you will write an essay that deals only with the difficulties
associated with the cooling of the
Unit 1 reactor at the Fukushima Daiichi power plant. Before
writing you
r essay, you should perform the
following calculations:
1. The Unit 1 reactor was a

boiling water

type reactor. These reactors generally work under
high
pressure and produce steam at
temperatures around
380C
. The power plant is a

heat
engine

, so
some of this thermal energy is released to the atmosphere and some is
converted to
electrical power.
Use the efficiency equation from chapter 2 (page 60) to estimate the maximum
possible effi
ciency
for this reactor.
2. The Unit 1 reactor was capable of producing
460MW
of
electrical
power. Assuming that the
plant

s
efficiency was about 10% less than the optimal efficiency you found
in the previous
question, what
was the
thermal
power output (in
units of MW) of the reactor?
3. The reactor was shut down quickly after the earthquake struck, and hence the nuclear chain
reaction
was halted. However, the highly radioactive fission fragments within
the reactor
continued to decay
and thus produce heat (t
he so

called

decay heat

). Combine your
estimate of
the thermal output
during normal operation with the information in your textbook (see te
xt above
Fig. 5.13) to estimate
the thermal output of the reactor just after the shutdown and one year after
the sh
utdown.
4. Heat can be removed from the reactor complex by allowing it to boil water. The process of
boiling
off a gallon
(
=
about
4 liters)
of water that is initially at
20C
takes approximately
9
.
8

10
6
Joules (
9
.
8MJ
) . Combine
this information with your previous work to com
pute the rate
that wat
er must be supplied (in gallons
per second) to carry away the heat so the reactor does not
heat up
and melt. Remember that a Watt
is a Joule per second, or
1
W =
1
J
/
s
.
Once you have completed these calculations, you should write your essa
y
concentrating on
t
he
difficulties
with keeping the reactor cool after the earthquake, even though
it had been
shut down.
Work at least some of the numbers you have calculated into your essay.