To give a fair answer;

    According to the United Nations Scientific Committee on the Effects of Atomic Radiation the normal concentration of uranium in soil is 300 μg/kg to 11.7 mg/kg.

    It is considered to be more plentiful than antimony, beryllium, cadmium, gold, mercury, silver, or tungsten and is about as abundant as tin, arsenic or molybdenum.[1]

Look around the landscape, if you can see granite then you will have high concentrations of both uranium and breakdown products of uranium such as radon gas in the environment already.

"Vast areas" is a good thing, it would mean the dense tips of weapons have been broken down and spread out across vast areas thus reducing the concentrations.

It's the high concentrations in small areas that you should worry about.

It should be noted the issue is the toxicity of uranium as an element that's the main cause for concern here .. "depleted uranium" is left over after processing to seperate out the radioactive isotopes for further use within the nuclear industry (weapons, power) and is less radioactive than 'regular' uranium occuring naturally in the environment.

[1] https://en.wikipedia.org/wiki/Uranium_in_the_environment