India Today published this piece in 1998 about the Pokhran tests. There are a bunch of interesting details that many of you may know.
Here’s a description of the plutonium transportation methods:
The manner in which the plutonium cores for the five tests were carted is an example of confident planning. Ten days before the tests, an Indian Air Force AN-32 took off from Mumbai’s Santa Cruz airport at night. Considering the cargo it carried, the security precautions were almost negligible. A couple of Sten gun-wielding commandos guarded the half a dozen wooden crates similar to the ones apples are shipped in. Inside those crates, protected by a metal shield, were perfectly shaped spherical balls of explosive-grade plutonium. Finely crafted by India’s premier nuclear establishment, the Bhabha Atomic Research Centre (BARC) at Trombay, each weighed between five to 10 kg.
At Jodhpur, two hours later, a convoy of trucks lined up at the airport and the crates were placed inside one of them. To make it seem a routine movement, no extra security was provided as the convoy sped to the range under the cover of darkness. Once at Pokhran, the crates were moved to makeshift labs, where other packages containing conventional explosives, detonators and triggers had been flown in, and scientists began mating the various components of the devices. They worked mostly at night to avoid detection by snooping satellites.
For Chidambaram, the chief designer of the Shakti round of tests, it was a vast improvement from the manner in which plutonium was carted when India carried out its first test in 1974. The man, who also played a key role in that test, recalls that then the plutonium crate was ferried by road. Since the scientists didn’t want to take any chances, Chidambaram hopped aboard the convoy of army trucks and stayed with it during the two-day harrowing journey through the desert.