nuclear

suggest why it is not possible to use all the Uranium 235 in the reactor fuel rods

too few neutrons produced to maintain the chain reaction 

B1 

probability of a neutron colliding with a uranium nucleus too low 

B1 

more absorption of neutrons in non–fission capture 

describe physical processes that take place in the moderator and control rods

control rods 

neutrons are absorbed 

B1 

by the nucleus of the boron/atoms 

B1 

moderator 

neutrons are slowed down 

B1 

when colliding with the protons/hydrogen nucleus 

advantages/disadvantages of using nuclear fuel to produce energy

 advantage: 
less mass of fuel used (1) because more energy per kilogram (1) 
[alternative: less harm to environment (1) because does not generate greenhouse gases (1) 
or any statement (1) argued (1)] 
disadvantage: 
hazardous waste (1) because fission products are radioactive (1) 
[alternative: long term responsibility (1) because waste needs to be stored for many years (1) 
or any statement (1) argued (1)] 

2017 Paper 2