Safety features of reactors and waste

Question 1

Why do nuclear reactors need to have safety features?

Answer 1

• protect workforce
• wider community
• and environment

Question 2

How is the reactor core made safe?

Answer 2

• thick steel vvessil designed to withstand high pressure and temperature in core
• absorbsbeta radiation and some gamma radiation and neutrons from the core

Question 3

Where is the core located?

Answer 3

• in a building with very thick walls which absorb the neutrons and gamma radiation that escape the reactior vessel

Question 4

What is the emergency shut-down system?

Answer 4

• designed to insert the control rods fully into the core to stop fission completely

Question 5

How are fuel rods controlled?

Answer 5

• the sealed fuel rods are inserted and removed from the reactor by means of remote handling devices
• the rods are much more radioactive after removal

Question 6

How do the fuel rods become more radioactive?

Answer 6

• fuel cans
  
  • before contain U-235 and U-238 which emit only alpha radiation and this is absorbed by the fuel cans
• after use emit beta and gamma radiation due to the many neutron-rich fifsion products that form
• spent fuel rods contain 239-Pu as a result of the absorbtion of neutrons
  
  • active alpha emitter if inhaled causes lung cancer

Question 7

What is legislation around radioactive waste?

Answer 7

• must be distributed by approved disposal companies to ensure the waste is stored safely in secure containers until the activity is insignificant
• disposal by dillution is banned

Question 8

What is high level radioactive waste?

Answer 8

• e.g. spent fuel rods
• contain many different isotopes

Question 9

How is high level radioactive waste disposed of?

Answer 9

• spent fuel rods removed by remote control and stored underwater in coooling ponds for upto a year because they continue to release heat via radioactive decay
• transferred to steel containers
  
  • unused fissionable isotopes removed
• stored in steel containers in deep trenches
  
  • dtored for centruies to prevent contamination of water supplies
  • geographically stable
  • or mixed with molten glass and stored as glass blocks

Question 10

What is the issue with long term storage?

Answer 10

• no one wants storage in locality
• or to be carried through their own locality

Question 11

What is intermedate-levle waste? How is it disposed of?

Answer 11

• low activity
  
  • e.g. container of radioactive materials
• encased in concetre and stored in specially constructed building with walls of reinforced concreete

Question 12

What is low-level waste?

Answer 12

• e.g. lab equipment and protective clothing
• sealed in metal drums and buried in large trenches