[iwwr]

That one had some fundamental problems due to the choice of graphite moderator. Another selling point: the ability to refuel while the plant is running also did not pan out. In the end these reactors had somewhere around 50% capacity factor, compared to more mainstream designs that used water (light or heavy) at 90%. They are also being decommissioned early, again, due to graphite cracking over time. That said, it's not unfeasible to imagine these problems being ironed out in the end, but rollout coincided with the Thatcher Era, which deprioritized industrial developmend and fundamental R&D. It was not a good deal to buy one of these 1st gen UK reactors, compared to a GE/Westinghouse LWR/HWR.