WHAT? the timer of the shutter has nothing to do with the the actual shutter speed. Using a timer for an old skool selfie has no relationship to blurriness in the exposure caused by too slow of a shutter speed.
You'll look a little bit transparent and be surrounded by fainter motion blur from when you were getting into position. I've done exactly this on moonlit nights, and the result looks completely consistent with the photo in the article. You also get ghostly duplicates if you hesitate as you get into position.
Could the shutter speed was an accident and the subject happened to pause enough to show up visibly on the image- much like the first photographed human, who was getting his shoe shined: http://mashable.com/2014/11/05/first-photograph-of-a-human/
If it's not a selfie, it's an extraordinarily lucky accident that there's a recognizable human in the photo.
ed: it's possible it was just really dark, and all the photos were exposed for that long. Someone wanted a picture of Korneyev, and he moved during the exposure. But the combination of "blurry person" and "crisp person" makes me lean towards the selfie hypothesis. Someone trying and failing to stand still won't wave a flashlight around. Someone rushing to get into a selfie shot might.
Of course, it actually contains two humans -- the man getting his shoes shined, and the one doing the shining. Somehow it's always bothered me that the shoe-shiner hasn't gotten equal credit. Arguably, he was actually first, since it looks like he's a bit closer to the camera.
A dumb camera would fire the flash immediately upon shutter click. The guy would not be able to to stand in front of the camera to allow the flash to bounce off his body
The result would be a "properly exposed" shot for anything except what was moving during the shot, which would presumably be him running so he could stand still and be exposed during the already running exposure.
I would imagine that someone working near the elephant's foot would be moving very fast.
This article is filled with inaccuracies and/or guesses (as other HN'ers are pointing out in other comments).
For example, it's increadibly unlikely the photographer of this image is still alive. Standing that close to that much radiation for long enough to setup a camera, walk around it and putz around for a while... I don't buy it. Majority of the workers involved in the containment died shortly afterwards, or developed terrible ailments due to extreme radiation exposure, leading to early death.
If were to take a 10 second photo, 4 seconds in one spot, 1 second moving and another 5 seconds in another spot I wouldn't be a full blur. The part of me moving only accounts for 1/10 of the entire exposure and the places where I stood still would be much brighter. I can exaggerate this by turning off my flash light when I was moving.
Your explanation still doesn't explain the lack of motion blur walking over to the spot, although we see the flashlight(s) blur. There also appears to be two distinct flashlight blurs.
There is only so much range a piece of film can achieve. I don't know how much you know about photos but exposure and light are usually discussed on a log(base 2) scale. Each exposure "unit" called a "stop" equates to doubling or halving the amount of light. So a 4 second exposure is 1 stop darker than an 8s one because it lets in half the light.
Assuming there are no other light sources we can assume the entirety of the exposure came from the flash light. There is a shadow behind and above the elephants foot which tells us the elephants foot was illuminated by a light below the camera. Assuming the guy had the camera at almost eye level, shines the flashlight at waste level could produce this kind of shadow.
Now let's say the guy turns the flashlight off walks over to where he is in the photo and starts moving the flash light more, shift position and does it again. You will not see him walk to the spot in the photo even if the room was not completely dark.
If he took a 60 second photo, he set the exposure for 30ish seconds of light from flash light and not from ambient light. This means the ambient light reflecting off the guy while he walked probably exposed a trail that is over 10 stops below what the light from the flash light did. In good conditions your average color negative film has about 7 stops of dynamic range or +3 from middle tones before turning completely white and -3 from going to complete black. It's not hard to set up a photo where you don't register because you're trail exposes below the range of the film. Many people do these kinds of photos and they are called "lightpainting".
This is very commonly done in landscapes where certain features of landscapes like trees and rocks are painted. You don't see the people walking around because they turn their lights off when they do it. They do produce walking smears but they account for such a small proportion of the overall exposure they don't show up in the final photo. I believe this what these guys do and notice no people in their photos:
However they might compositing images. Here is another example:
I've personally done photos like that in a single long exposure. I'm sure the photos I linked have lots of photoshop to get them perfect to get them perfect the principal stands. I'm assuming a lot of photography sophistication that the elephant foot photographer may or may not have but how knows!
Doing some back of the envelope calculations, with a somewhat bright room, you could take the exposure in anywhere from 15s to 2m which is plenty of time to walk across the room.
Of course all this is irrelevant because timers (mechanical and electronic) had been standard features in cameras for decades by 1996. It looks to me like he just moved in the midst of a 2 or 3 second exposure.
In addition, maybe it's just the lighting effects, but the figure standing almost upright is wearing what appears to be a yellow jumpsuit, while the figure bending over is wearing white. The red box on their hip is probably some sort of geiger counter, and most folks getting this close probably had one.
Even if the camera was put into lead encasing, the shielding shutter was opened for quite a long time and pointed directly at the source of the gamma rays.