The report by Miller Research, commissioned by the Welsh Government, investigated the capability of Welsh businesses to take advantage of opportunities in the sector.
It is estimated that planning and construction costs for the Wylfa Newydd power plant in Anglesey will be about £14bn, with a further £3.3bn contributed once it is operational.
About a third of the costs are set to be spent in Wales, with up to 6,800 people expected to be employed on the construction.
Decommissioning at Wylfa should contribute £630m, with an additional £310m contribution from continuing decommissioning at Trawsfynydd.
Between 2013 and 2033 planning, building, operation and decommissioning is forecast to contribute £5.7bn to the Welsh economy.
The report cautioned that Wales could miss out on the impact if businesses do not take advantage of opportunities.
Economy Minister Edwina Hart said: “This report clearly illustrates the scale of the potential investment, the opportunities for Welsh businesses and some of the issues and perceptions that need to be addressed in order to maximise the potential benefits.
“It is a once in a generation opportunity and a concerted effort is needed across the board – by businesses and industry and the public and private sectors if we want to ensure that as much of that investment as possible in spent in Wales.”