Well there are a slew of nickle based "superalloys" that get used in the nuke world. Grouped under the trade name of INCONEL, there are a few different ones. When I was at the papermill we had 12in ball valves that had X-750 ring seats. This alloy got used in other things that I used to work with in a past life that I can't name because unlike some folks, I will go to jail for revealing classified information. X-750 is tough stuff, I was shocked to see how badly it was corroded and eroded by the stock, but compared to how SS ring seats faired, it was far superior.
Now those fasteners, There is a pretty good chance they could be one of the PH stainless steel alloys, like 17-4 PH. Those have a high resistance to neutron embrittlement, even though they have a high cross section for absorption of neutrons.
The actual neutron embrittlement of the large forgings like core vessels and primary loop piping is greatly offset by the annealing effects of operational temperatures.
Now as for it being a BWR, well, while I never worked on one, the GE design is as good as can be expected, Fukushima was a statistical outlier when it comes to safety engineering. They had a 1000 year surge, (which btw, no one built to protect against) which blew expected (and protected against) levels away. Couple that with the disjunction of the earthquake, you had a perfect storm. The main problem was the lack of cooling to the spent fuel pools, (which like here in the US were overloaded). It was when these boiled dry, and the cladding failed, did we get the massive release of fission products. The right answer to fix that, get spent fuel cooled down and on it's way to reprocessing, (which is nearly dead in the US), or on its way to long term disposal, (not gonna happen, rot in hell Harry Reid.)
Chernobyl, well, when you build a reactor with a positive coefficient of temperature reactivity. Deliberately run it in a manner designed to minimize your scram reactivity by having the top and bottom rods in the least reactive positions. Oh and with no actual containment, just a metal shed. And then drive temperature up by cutting off steam demand while reducing coolant flow. Well, that's how you end up not needing a nightlight in Minsk, the glow will light your way home...
If you're really worried about your exposure, stay away from the sun, granite, and bananas.