As of early 1963 the reactor within the secured area appeared to be complete, and foundations suitable for a second reactor just outside the walled area were evident. In late 1964 US intelligence estimated that this reactor went into operation in late 1963 or early 1964 [it might have gone into operation earlier though this was judged unlikely]. While a larger plutonium production installation may have been planned, there were no indications that a second reactor was under construction, and as of September 1963 construction was continuing throughout the site, including some fairly substantial work around the building which houses the reactor. Photography of March 1964 indicated that major construction at the site --including service roads and additional security provisions -- had apparently been completed.
The inferred construction history of the Baotou facility suggested that the earliest date by which the reactor could have reached criticality was probably early 1962. A minimum of two years would be required before a first all-plutonium device could be available -- about one year for fuel element radiation after the reactor becomes critical, and an additional 9-12 months for cooling of the radiated fuel, chemical separation of the plutonium, and fabrication of the device. Hence, the earliest date for a nuclear detonation by China was estimated as early 1964, assuming no unusual difficulties in producing kilogram quantities of plutonium or in fabricating their first nuclear device. A more likely date was assessed as being late 1964 or early 1965.
The size of the initial Baotou reactor (estimated at between 20 MWt and 50 MWt) would limit plutonium production to an amount sufficient for one or possibly two weapons per year.Initially US intelligence estimated that the first Chinese nuclear weapons test in October 1964 used Plutonium from this facility, though subsequent analysis of the debris from the test immediately demonstrated that the first Chinese nuclear weapon used Uranium, which led the US intelligence community to realize that the U-235 plant at Lanzhou had in fact become operational sooner than anticipated.
