Producing some kind of nuclear explosion is mostly only about procuring the raw materials. Getting to significant yield is the actual hard part as it involves precision machining, measurements and timing.
Machining heavy metals is complex problem in itself even without requirement of extreme precision. It is hard to procure machining equipment with sufficient precision and tooling capable of machining hard metals without raising lots of red flags.
Almost anything that is capable of switching of significant powers with small or repeatable latency is essentially non-exportable with the reasoning that it is not useful for much else than triggering nuclear weapons (one could think of lots of other applications, but the devices are too bulky and expensive for most of them).
Machining heavy metals is complex problem in itself even without requirement of extreme precision. It is hard to procure machining equipment with sufficient precision and tooling capable of machining hard metals without raising lots of red flags.
Almost anything that is capable of switching of significant powers with small or repeatable latency is essentially non-exportable with the reasoning that it is not useful for much else than triggering nuclear weapons (one could think of lots of other applications, but the devices are too bulky and expensive for most of them).