Hevach
Senior Member.
Source: https://twitter.com/thenrthstar/status/1496976049275559936
There's some tweets about radiation increase from the Chernobyl reactor site. There was speculation of Russia reactivating the functional reactors to support the eastern grid while they attack in the west, but I doubt this is any sign of that. Bringing one online safely shouldn't do this, and bringing one online unsafely should do a heck of a lot more.
Radiation spikes from Chernobyl aren't that unusual, there was one a few months ago much higher than this. Water leaking in or debris breaking loose near a corium deposit can cause a small mass to go near critical and produce a lot of excess emissions, but it usually goes away in a few days.
This one isn't even particularly serious, you could hang out in it for a month before hitting the annual safety limit for radiologists. Russia is moving tanks through the area so who knows what has been kicked up or unburied from the ground.