[Music] I'm welcome back to three times I think a UK by the end of this video you should be able to describe what's meant by irradiation on by radioactive contamination you should then be able to describe the hazard associated with these and finally you should be able to describe the precautions we can take against these hazards of the last few videos we've looked at where you are diviner topes remember that these decay and they emit radiation from their nuclei we saw that radiation can be ionizing in other words to confirm charged atoms called ions now there's a very big risk linked to ionizing radiation under that is that it can increase the risk of cancer in humans so we're going to start by looking at irradiation irradiation is exposing an object to nuclear radiation for example alpha beta or gamma radiation or neutrons a good example of this is for sterilization in other words to kill bacteria lots of medical equipment needs to be sterilized and in many cases this is done by heating but some object cannot be heated so for these we use gamma radiation produced a radioactive isotope so here's the object to be sterilized in this case it's a syringe we've placed this inside a sealed plastic wrapper that's to stop bacteria entering after we sterilize the object now we place the object near a radioactive isotope that emits gamma radiation that's inside a lead shield to protect workers from the radiation when we withdraw the internal lead shield this allows gamma radiation to a radiate the object the gamma radiation kills any bacteria present now one key fact that you have to learn is that what an object irradiated like this the object does not become radioactive that's because the object only comes in contact with the radiation but not the radioactive isotope itself now as I said before ionizing radiation can increase the risk of cancer so people who work with radioactive isotopes have got to take precautions the first precaution is shielding to stop the radiation we saw in an earlier video that different types of radiation have different penetrating powers so alpha radiation which has got a very low penetrating power can be stopped by wearing gloves however ether and gamma radiation are more penetrating for these we can use lead for example in this LED apron however with high levels of radiation a lead apron may not be enough this man's working with nuclear fuel he's protected from the radiation by lead Wars on by a screen made a glass containing a lead now another way we can reduce exposure to radiation is by using a radiation writer such as this one now this does not stop radiation but I can mean that we can measure how much radiation is being received if the person has received too much radiation we can stop them from working with regular active isotopes remember that with a radiation you are not contaminated with the radioactive source so you yourself do not become radioactive okay let's look at radioactive contamination radioactive contamination is when unwanted radioactive isotopes end up on other materials now this is harder this as the radioactive atoms decay and they emit ionizing radiation with radioactive contamination you now have the radioactive source on you or in you and you could get a large dose of radiation now the level of hazard depends on the type of radiation emitted alpha emitters can be very dangerous as other particles are very strongly ionizing however alpha particles are easily stopped by dead cells on the skin surface there is one way but alpha emitters can be very dangerous and that if they're inhaled for example on contaminated dust or swallowed for example on contaminated food now the alpha particles crash into living cells and damage their DNA beta particles are less ionizing than alpha however bigger particles can easily penetrate into the body where they can damage cells gamma rays are only weakly ionizing and they can pass into the body and then out again so they're usually less hazardous than alpha or beta radiation now over the years scientists have explored the effect of radiation on humans it's really important that these studies are published and then shared with other scientists this allows the findings to be checked now scientists call this process peer review and it's important that you learn that remember that you'll find plenty of questions on irradiation and contamination in my vision workbook and you can get that by clicking on the link above [Music]