[syhprum (OP)]

The "little Boy" type of nuclear bomb was vastly expensive to produce with the separation techniques available in the 1940's after the development of plutonium implosion type weapons were anymore manufactured or tested? .
   

[Petrochemicals]

Is this not what iran is being moaned at about, by 5 nuclear armed states and with the moanings of israel, also nuclear armed, on the border of pakistan, nuclear armed, and not far from india who is also nuclear armed.

[Bored chemist]

At least in part, yes.
https://en.wikipedia.org/wiki/RDS-4
used U235

[evan_au]

There were many Uranium and Plutonium bombs detonated after the nuclear attacks on Japan*, testing new models of nuclear weapons. Even the "Hydrogen Bomb" was triggered by a small fission bomb.

Many of these explosions were in the atmosphere, producing a distinctive radioactive marker in the geological record (including human bones). Atmospheric tests were halted after by a treaty in 1963.
https://en.wikipedia.org/wiki/Partial_Nuclear_Test_Ban_Treaty

Many nuclear tests have continued underground, including recent tests by North Korea, Pakistan and India.
But many countries halted underground testing after 1996.
https://en.wikipedia.org/wiki/Comprehensive_Nuclear-Test-Ban_Treaty

*the Japanese emperor Hirohito said that "the war situation has developed not necessarily to Japan's advantage", only a week after the atomic bombings of Hiroshima and Nagasaki.
See: https://en.wikipedia.org/wiki/Meiosis_(figure_of_speech)#Examples

[Bored chemist]

There were many Uranium and Plutonium bombs detonated after the nuclear attacks on Japan*, testing new models of nuclear weapons. Even the "Hydrogen Bomb" was triggered by a small fission bomb.

Many of these explosions were in the atmosphere, producing a distinctive radioactive marker in the geological record (including human bones). Atmospheric tests were halted after by a treaty in 1963.
https://en.wikipedia.org/wiki/Partial_Nuclear_Test_Ban_Treaty

Many nuclear tests have continued underground, including recent tests by North Korea, Pakistan and India.
But many countries halted underground testing after 1996.
https://en.wikipedia.org/wiki/Comprehensive_Nuclear-Test-Ban_Treaty

*the Japanese emperor Hirohito said that "the war situation has developed not necessarily to Japan's advantage", only a week after the atomic bombings of Hiroshima and Nagasaki.
See: https://en.wikipedia.org/wiki/Meiosis_(figure_of_speech)#Examples

There were plenty of nukes- but how many used isotopic separation of uranium, rather than chemical separation of plutonium?
U235 is arguably doing it the hard way.
But using plutonium needs a reactor program.

[evan_au]

But using plutonium needs a reactor program.

I understand that a reactor operated to maximise thermal energy output is operated rather differently than one operated to maximise plutonium output.

A difference that would be obvious to international nuclear inspectors.