Physics - Nuclear stuff

Question 1

describe the role of control rods and moderators in nuclear reactors and their effect on the rate of reactions

Answer 1

Control rods are made from materials such as boron which absorb neutrons to reduce the rate of reaction or fully stop it (when completely lowered)

Graphite or water is used as a moderator, to slow down neutrons to make them more easily absorbed by the uranium nuclei to increase reaction rate.

Question 2

What is the vessel made out of and why is this useful?

Answer 2

It is made of thick steel to cope with the high temperatures and pressures.

Question 3

What does the concrete shield do?

Answer 3

concrete shield prevents gamma rays and neutrons leaving the core.

Question 4

What is nuclear fission used for?

Answer 4

Nuclear fission is used to release energy from fissionable nuclei.

Question 5

How does nuclear fission work?

Answer 5

A neutron is fired at the uranium nucleus, which splits into two daughter nuclei, releasing energy and two or three neutrons. These neutrons can then split more uranium nuclei in a process called a chain reaction. These need to be controlled in a nuclear power station.

Question 6

How do nuclear power stations produce electricity?

Answer 6

By using nuclear fission

Question 7

What is nuclear FUSION?

Answer 7

Nuclear fusion is the joining of two light nuclei to form a heavier nucleus. The heavier nucleus has slightly less mass than the two lighter nuclei as some of the mass in converted.

Question 8

irradiated?

Answer 8

An object that has been exposed to ionising radiation.

Question 9

contamination

Answer 9

the unwanted presence of a radioactive substance on someone or something

Question 10

activity

Answer 10

the number of radioactive decays per second.

Question 11

becquerel

Answer 11

the unit activity (1Bq = 1 decay/second)

Question 12

sievert

Answer 12

a unit of radiation dose (Sv)

Question 13

count rate

Answer 13

number of decays/second detected by a Geiger counter

Question 14

Geiger counter

Answer 14

device used to measure count rate

Question 15

background

Answer 15

radiation present all around us from various sources

Question 16

half life

Answer 16

amount of time for activity of a radioisotope to half

Question 17

dose

Answer 17

amount of ionising radiation a person receives

Question 18

ionisation

Answer 18

the removal (or addition) of electrons from atoms to create ions

Question 19

isotope

Answer 19

atoms with the same number of protons but a different number of neutrons

Question 20

what is an alpha particle

Answer 20

an alpha particle is identical to that of a helium nucleus. It contains two protons and two neutrons

Question 21

What is a beta particle?

Answer 21

A beta particles is a fast moving electron which is emitted from the nucleus of an atom undergoing radioactive decay.

Question 22

What are advantages of nuclear energy?

Answer 22

-Not as polluting as burning fossil fuels - saves 1.8m people
-reduces CO2 emissions - 64 giga tonnes of greenhouse gases not pumped out by using nuclear energy
-relatively clean and doesnt contribute to global warming
- 1 tonne of thorium = 3500000 tonnes of coal
-could lead to new technologies

Question 23

Disadvantages of nuclear energy

Answer 23

-can be used to make extremely destructive weapons
-contains poisonous chemicals like plutonium
-bad for environment
-7 major accidents have already happened which has killed thousands and contaminated land.