One may certainly visit the Chernobyl area, including even the exclusion zone, which is a 30 kilometre radius surrounding the plant, all of whose reactors are now closed. Although some of the radioactive isotopes released into the atmosphere still linger (such as Strontium-90 and Caesium-137), they are at tolerable exposure levels for limited periods of time.
Some residents of the exclusion zone have returned to their homes at their own free will, and they live in areas with higher than normal environmental radiation levels. However, these levels are not fatal.
Background radiation in Chernobyl Zone is very low, and normal. When assessing the danger of a radiation dosage – you have to consider the level of radiation and the time spent near the source. It doesn’t mean that one is safe to live near Sarcophagus or eat food that grown anywhere there. But the level of radiation is perfectly safe enough to enter the restricted zone for a day or two.
It’s comparable to the excess radiation acquired on a long intercontinental flight. We get about 25 times the normal background radiation at a cruising altitude of 8000m.
Anything below 0.05 Sv can be considered as entirely harmless. The expected dose you will get from the trip is around 0.010 – 0.015 mSv, which is 0.00001 Sv.
There are no a reasonable explanation to this question. Somehow people are drawn to the place. They want to feel the unseen killer lingering around, the sense of imminent danger. Maybe they are just interested in the whole accident and its aftermath. But one has to agree, (fortunately) there is no place like this on Earth.
There are many measurement units related to radiation, all a little different in their definition. Most people are interested in its effect on humans, the radiation dose or the dose rate. The exposure to radiation is measured in Sieverts (Sv), and because this is a large unit its fractions milli and micro Sieverts (mSv, μSv). The dose can be simply defined as the accumulated exposure in any given time, the dose rate as the dose received in a given time frame, usually an hour (mSv/h, μSv/h)…
For long time exposure, the maximal safe level is usually considered to be 0.30 μSv/h – depending on the local laws and regulations. Mind you, this means that you can be exposed up to this level for all your life, and still be fine. The typical background radiation will be somewhat lower, around 0.10 – 0.30 μSv/h. You can easily calculate the annual dose from that.