Chinese nuclear scientists have developed a type of atomic reactor that is small, efficient and relatively safe. Military engineers have since used them to upgrade Battlemaster and Overlord Tanks. The more efficient nuclear engines give these tanks a 50% increase in speed. Take note that, should these tanks be destroyed in battle, the engine tended to explode violently and left behind trace amounts of radiation. This obviously posed a problem for enemy and friendly troops alike, but could be remedied with the Isotope Stability upgrade.
Tsing Shi Tao's tanks come with this upgrade pre-installed. Shin Fai cannot gain this on his own, but can capture another general's nuclear missile silo to research it.