The USAF WC-135C Constant Phoenix might be investigating a spike in radioactive levels in Norway. Someone speculates the release of this radionuclide could be the effect of a Russian nuclear test.

https://theaviationist.com/2017/02/19/u-s-air-force-deploys-wc-135-nuclear-sniffer-aircraft-to-uk-after-spike-of-radioactive-iodine-levels-detected-in-europe/