Drilling has started at the Napperby uranium project north-west of Alice Springs.

It is the second year of the core feasibility study being conducted by South Australian based mining company Top Energy Limited.

The drilling will last five months.

Top Energy Limited's managing director Greg Hall says by the project's end the company will be in a better position to know how much the resource is worth.

"We have a small resource of around 670 tonne of contained uranium and we think the figure - our target to trying to achieve an economic project - is around the 5,000 to 6,000 mark," he said.

"That's the size of a small uranium mine such as the Beverley mine or the Honeymoon mine in South Australia."