Radiation level risk: mSV, exposure and current status of chernobyl area

Question

I was watching this two videos from youtube.

One is a documentary about Chernobyl disaster: https://www.youtube.com/watch?v=d5vlk_d6hrc

Another is a random personal video: https://www.youtube.com/watch?v=ejZyDvtX85Y

I was greatly impressed by the people in this videos. In the first video a major (probably on duty in Chernobyl) is assisting the guy doing the documentary to show him around (Chernobyl and near abandoned city Pripyat). He is seemingly walking and touching radioactive stuff (suits of the firefighters in that day lying in the Pripyat hospital, metals near plant 4, used cars etc.) The radioactive counter is beeping heavily, sometimes reaching 400 mSV. They were not using any suits.

In the next video, someone pulled radioactive fuel from Chernobyl (tiny rod fragment), took it home and examined it with bare hands.

They seem to have no idea. Is walking around Charnobyl, touching and staying near stuff that are highly radioactive dangerous? Even touching nuclear fuel with bare hands? How can someone go into the hospital room where those firefighters were remedied? Isn't that extremely dangerous? How come the suits are just lying there? Shouldn't they be decontaminated or something?

This random videos in the youtube also raise another question. In terms of mSV (that seems to be the unit for radioactivity for cheap detectors, so please don't explain with other units, e.g. Sievert, Gy, Rontgen etc), how much is bad? Those people in the Pripyat hospital were exposed to 400+ mSV with no suits? Is Chernobyl safe now to visit and wonder around ?

Answer 1

XKCD Radiation chart puts everything in perspective. 1 banana to 1 hour near Fukushima.

• If you're a beginner in the field, think of contamination(and other radioactive stuff) as the poo and radiation as the stink.
• You mentioned they weren't wearing suits. The suits are only used for preventing personnel contamination and have little impact of exposure. So they have value, but not in lessening what I think is your concern, the radiation exposure.

Is walking around Chernobyl, touching and staying near stuff that are highly radioactive dangerous?

• Highly radioactive, yes. Touching puts your body in the highest radiation field since radiation decreases by the square of the distance from the source.
• The level of risk is higher if the source is more radioactive or if the object has loose contamination (if touching it).
• It would be dangerous to stay in certain areas for long, but most of the area is not dangerously radioactive.
• Prolonged exposure to even low-medium levels of radiation increases cancer risk.

Even touching nuclear fuel with bare hands?

• If it is spent fuel, YES. If not, no. I touch new fuel every year. Uranium is only mildly radioactive.
• Even tiny fragments of spent fuel would be VERY radioactive and touching one poses not only a significant exposure risk, but also the possibility of internal contamination.
  • The small speck she touched was 17 mSv/hr. See below for calculating her dose from this. Regardless, it would be dumb to touch that or be near it for longer than a few minutes.

How can someone go into the hospital room where those firefighters were remedied? Isn't that extremely dangerous?

• There is an exclusion zone around Pripyat, which is illegal to enter unaccompanied. It would be dangerous to stay in certain areas for long, but most of the area is not dangerously radioactive.

How come the suits are just lying there? Shouldn't they be decontaminated or something?

• This is probably due to no one wanting to pay to clean up that area. Contamination cleanup is difficult and expensive.

In terms of mSV (that seems to be the unit for radioactivity for cheap detectors, so please don't explain with other units, e.g. Sievert, Gy, Rontgen etc), how much is bad? Those people in the Pripyat hospital were exposed to 400+ mSV with no suits? Is Chernobyl safe now to visit and wonder around ?

• From the XKCD chart, 100 mSv is the lowest yearly dose ever linked to cancer. One would benefit from providing themselves significant margin to this number, even an order of magnitude or two.
  • Also, note the dose received from an hour at Chernobyl, but also that it varies heavily with location and vicinity to sources.
• They are measuring radiation rate (400 mSv/hr, not just mSv). To get exposure, you multiply by time.
  • 0.1 hrs (6 minutes in the fire fighter outfit room) X 400 mSv/hr = 40 mSv
    • (about what you are allowed to get in a year as a radiation worker)
  • NOTE, they were not full-body exposed to 400+ mSv/hr, as that was an on-contact reading and their entire bodies would not be contacting the source. The field at the height of their head would have been significantly different. So their whole body dose was significantly below this, but their feet may have received 40 mSv.
  • Usually, you measure general area radiation to determine exposure (take a measurement using the detector at waist height).
• Yes, you could probably visit Pripyat and the surrounding area safely. High level radiation fields aren't everywhere but known contaminated and radiation areas should be avoided. Eating, drinking, and breathing in the area presents the possibility of getting internal contamination from anything you touched. E.g. if you grabbed a handrail that had loose contamination (dust) and then ate a sandwich after without washing your hands.
  • The girl touching her face while handling fuel fragments and contaminated earth in the video shows how little she understands about her ability to be internally exposed.