A group of uranium mining companies saw their stock prices...

A group of uranium mining companies saw their stock prices plunge Monday after news emerged that a nuclear power plant in Southeast China flagged a performance issue.

It was yet another unnecessary investor meltdown, writes Jinjoo Lee.Canadian uranium mining companies Cameco and NexGen Energy dropped 10% and 9%, respectively, and a basket of uranium-related companies tracked by the Global X Uranium ETF fell 6.5%.

They regained some of that lost ground by Tuesday afternoon.Monday’s reaction came after CNN reported that the U.S. government was assessing a report of a leak—not of radiation but of inert gases—at a Chinese nuclear power plant co-owned by two Chinese energy companies and French energy company EDF. The market response is almost comparable to what happened after the Fukushima nuclear accident in 2011, which led Cameco shares to fall almost 13%. But that turned into a major hit to nuclear fuel demand affecting the industry for years. Monday’s drop looks like an outsize reaction.Uranium mining companies tend to operate on multiyear supply contracts with utilities, so there is little risk that a nuclear power plant would immediately pull back buying from these miners. Instead, the risk of a nuclear incident is if it saps future demand—either by shutting down the nuclear power plant in question or if the incident changes governments’ and companies’ decisions to build new ones in the future. Neither seem likely, but nuclear stocks have sold off brfore on similar headlines.