Surprised this station seems to post-date that? Seems like it would have been handy to have in the Cold War. Then again, Russia has long had a mining presence on Svalbard so maybe that has something to do with it.
This triggered an investigation which traced the contamination to the improper disposal of the active element of a retired medical radiotherapy machine that used cobalt-60 - the radioactive cobalt ended up mixed with a large batch of other scrap metal, contaminating (among other things) ~6,600 tons of rebar, much of which had already been shipped at the time this was discovered...
https://en.wikipedia.org/wiki/Ciudad_Ju%C3%A1rez_cobalt-60_c...
Not only a mining presence [1]: "After the war, the Soviet Union proposed common Norwegian and Soviet administration and military defence of Svalbard. This was rejected in 1947 by Norway, which two years later joined NATO. The Soviet Union retained high civilian activity on Svalbard, in part to ensure that the archipelago was not used by NATO."
They did have gamma, neutron, and X-ray detectors too but I’d guess those were also tuned to detect detonations rather than small background changes. That might not be feasible from so high up and it would square with the Velas’ role in discovering gamma-ray bursts.