As a potential weapon material pure uranium-233 is more similar to plutonium-239 than uranium-235 in terms of source (bred vs natural), half-life and critical mass, though its critical mass is still about 50% larger than for plutonium-239.
The Soviet Union detonated its first hydrogen bomb the same year, the RDS-37, which contained a fissile core of U-235 and U-233 [REF].