The pre-feasibility study reduced the proposed mine life from 15 to 9 years and increased initial capex 5% to C$1.25 billion (US$0.95 billion), but also increased average annual production 37% to 25.4 million pounds U3O8 and increased the grade by 79%.

Compared with the 2017 preliminary economic assessment, the PFS showed a 64% increase in average annual after-tax net cash flow to $909 million (US$693 million).

It put the after-tax NPV (8% discount) at $3.7 billion (US$2.8 billion) and IRR at 56.8%, with a 1.2-year payback, using a long-term uranium price of US$50/lb.

The uranium spot price, which has averaged $23.89 over the past year, yesterday reached $28.80/lb, its highest since late March 2016 due to supply cuts and demand on the spot market to fulfill commitments.

NexGen's PFS estimated all-in sustaining costs of C$12.11/lb (US$9.24/lb).

CEO Leigh Curyer said with these strong PFS results, NexGen was expediting Arrow to feasibility by initiating a two-stage 125,000m, 10 rig high-density drilling programme, bringing it forward to start next month.

"This will be the largest drilling, geotechnical and hydrogeological focused program in the history of NexGen," he said.

The company said its $133 million (US$101 million) in treasury fully funded its upcoming and planned programmes.

Its Arrow deposit is part of the company's Rook I project in Saskatchewan's Athabasca Basin.

NexGen shares closed up 13.73% yesterday to C$3.23, capitalising it over $1.1 billion.

Other TSX-listed uranium stocks rose a similar amount yesterday.