Why? Isn’t it in the national interest of a government to preferentially use foreign sources of uranium to preserve domestic sources?

there is a strong environmental reason for this without even considering that there are plenty of alternatives to nuclear energy that do not require destroying the environment, because everything has consequences. destroying entire ecosystems puts many species at risk, mining requires huge amounts of water, money, and often involves legal slavery. plus, the extraction and processing process releases significant amounts of CO2 due to heavy machinery and refining. So thankfully, your country took a good decision