Frequently Asked Questions

Watches can contain radioactive compounds to make them glow in the dark. 
 
In earlier times, radium containing paint was used. Radium is a natural radioactive compound that emits alpha, beta and gamma radiation. The gamma radiation can penetrate through the watch, causing a (usually small) radiation dose to the person wearing it. 
 
Nowadays, other radioactive substances are used in these glowing paints, like tritium. Tritium only emits low energy beta radiation. This radiation is stopped completely by the window of the watch. It can not even penetrate more than a few millimetres of air. These watches will not give a radiation dose.
 

No, your lunch pack is still safe to eat.
The X-rays will penetrate the bag and everything in it. Part of the radiation will be stopped in by the materials in the bag, that is why you can see the contents. This does not cause the bag to become radioactive, only some radiation went through. Compare it to a window: the sun shines its light through the window all day, but this does not make the window sending out light afterwards.

Sometimes radioactive substances are administered to patients in hospitals. This is done at the nuclear medicine department. One of the reasons is to visualise certain problems in the body, like tumours, or to treat them.
 
 
When a patient is injected with a radioactive pharmaceutical, he will emit radiation. The level of radiation will decrease in time, because the patient excretes the radioactive compount in his urine, and because the radioactivity decreases during radioactive decay. Patients are only allowed to leave the hospital after the radiation level has decreased below a certain level. At that moment, it is not dangerous for bystanders to be near the patient.
 
It is still recommended that the patients sleeps alone for a few days, and that he should not take small children on his lap. These simple rules, that a patient receives from his hospital, help to decrease the radiation exposure of bystanders even more: more distance means less radiation dose. Little children are more sensitive to radiation, that is the reason to keep some extra distance.
 
To make a long story short: it is no problem to take your children to visit their grandfather, but it is better not to have them cuddle their grandfather for too long.

X-rays are ionising (nuclear) radiation, just like gamma radiation. Too much exposure may lead to biological harm. The radiation exposure of one or two X-ray pictures does not give any increase of risk, but a dentist shoots hundreds of X-ray pictures per year. It is better not to be exposed every time, if it is not really needed. That is why a dentist stands in a different room when making the pictures.
 

During the Fukushima incident, a large amount of radioactivity was released in the environment. For a large part the activity came in the sea water, for a smaller part on the land. The zone directly surrounding the nuclear power plant is still not accessable. In other places in Japan, the radiation levels are not or only slightly increased, compared to normal background levels of radiation. Even during the first weeks after the incident, these levels were still quite low.
 
The radiation dose you are expected to receive during your visit to Japan is hardly more than the normal background radiation dose, and much less even than the dose you will receive during the flight because of cosmic radiation.
 

Nuclear radiation (or better: ionising radiation) can not be perceived by human senses, so you can not feel it. When the radiation dose in the skin is very high, e.g. during radiotherapy, reactions in the skin cells may lead to itching and in extreme cases to painful skinburns. These reactions are not instantaneous, but can only be felt some time afterwards, just like sunburn. The pain in the skin can not help as a warning to irradiation.
 
Some people have reported that they could feel if an X-ray apparatus was switched on or not, by some sensations in their skin. These people were found not to feel tingling because of the X-rays themselves, but because of static electricity that is formed in the air as a result of the radiation.