This dome in the Pacific houses tons of radioactive waste – and it's leaking

Given the complete and total lack of useful numbers, plus general knowledge of this sort of thing (I became a nuclear war survivalist in 1968 when my mother became a Civil Defense Block Mother), I suspect not bad at all. E.g. the "plutonium has a half-life of 24,000 years!!!!!!" testifies to its relative safety, the longer the half-life, by definition the less intense the radiation from it; compare to the 138 years of infamous polonium-210.

There was also some confounding of the results from one particularly bad "oops" with normal testing, that of our first "dry" thermonuclear device, which had a yield much greater than expected because the fraction of lithium-7 in it turned out to generate tritium very well; that plus suboptimal weather had a very bad unplanned result for the local environment: https://en.wikipedia.org/wiki/Castle_Bravo

These sorts of articles are written by polemicists with no understanding of the physics and little if any of the biology (I'll bet they eat bananas! https://en.wikipedia.org/wiki/Banana_equivalent_dose), let along a willingness and almost certainly ability to "do the math". In this case, to do back of the envelope calculations of how this would dilute if released into the rather large Pacific Ocean. I wouldn't be surprised if it would be barely noticeable.

All that said, there could most certainly be local effects, but by now I'd expect them to be small, if not de minimis compared to the fallout from the tests, especially Castle Bravo.

And we should keep some perspective: allowing the Soviet Union to win would have resulted in Communists killing substantially more than the minimum estimate of 100 million people in the 20th Century. Somehow the good things we do never come up in articles like this designed to trash the US, which in the case of a UK paper like The Guardian demonstrates stunning ingratitude.