You can walk to the Port Chicago site; I've been there. It's a nice walk by the Suisin Bay on the Carquinez Straight between Martinez and Pittsburg. There is a
national historical monument to the disaster, but it's not at the explosion location.
The speculation that it was an atomic explosion is a paranoid fantasy. Given the technology of the time, a ground level explosion would have produced so much radioactive fallout that it would still be detectable today.
Then there is the issue of the situation at the loading docks. This was the era of the racially segregated US military, and the majority of the sailors at the installation were African American sailors, with white officers. Most of the people killed were the black sailors. Afterwards, some of the men refused to resume work under such dangerous conditions, and were courts-martial for mutiny and jailed.
Given the reality of a segregated Navy, it is inconceivable that something as important as an atomic weapon would be assigned to the Port Chicago facility. In the real world, the nuclear components of the bombs dropped on Japan were accompanied by scientists and technicians from Los Alamos for assembly on Tinian before the flight missions.
While this training was taking place, the components of the first two atomic bombs were shipped to Tinian by various means. For the uranium bomb code-named "Little Boy", fissile components consisted of a cylindrical target and nine washer-like rings that made up the hollow cylinder projectile. When the bomb detonated, these would be brought together to create a cylindrical core. The uranium-235 projectile and bomb pre-assemblies (partly assembled bombs without the fissile components) left Hunters Point Naval Shipyard, California, on 16 July aboard the cruiser USS Indianapolis, arriving 26 July. The Little Boy pre-assemblies were designated L-1, L-2, L-3, L-4, L-5, L-6, L-7 and L-11. L-1, L-2, L-5 and L-6 were expended in test drops. L-6 was used in the Iwo Jima dress rehearsal on 29 July. This was repeated on 31 July, but this time L-6 was test dropped near Tinian by Enola Gay. L-11 was the assembly used for the Hiroshima bomb. On 26 July three C-54s of the 320th Troop Carrier Squadron left Kirtland Army Air Field, each with three of the uranium-235 target rings, and landed at North Field on 28 July.
The components for the bomb code-named the Fat Man arrived by air the same day. The bomb's plutonium core (encased in its insertion capsule) and the beryllium-polonium initiator were transported from Kirtland to Tinian by C-54 in the custody of Project Alberta couriers. Three Fat Man high explosive pre-assemblies designated F31, F32, and F33 were picked up at Kirtland on 28 July by three B-29s, two from the 509th and one from the 216th AAF Base Unit, and transported to North Field, arriving 2 August. The B-29s were Luke the Spook and Laggin' Dragon of the 509th, and 42-65386, a phase 3 Silverplate of the 216th AAF Base Unit. F33 was expended during the final rehearsal on 8 August, and F31 was the bomb dropped on Nagasaki. F32 presumably would have been used for a third attack or its rehearsal.
Assembled nuclear bombs were never shipped in a configuration where a nuclear explosion could occur. Claiming otherwise is ridiculous. It's the fantastic logic of a day dreaming 9 year old boy.
So I suggest that you perform an experiment. Get a radiation detector and go to the site. Spend a day looking around. If the weather is nice you will have a wonderful time. And you will find no trace of radiation, or any sign of an explosion at all. Then you can take the radiation detector home and look for the radioactive mind control scorpions that the CIA has planted in your basement.