A 100-year-old steel mill that once forged guns for the Japanese Imperial Navy has hit a production bottleneck that threatens to derail more than Ј150 billion of global nuclear power-plant construction.

The capacity shortage at Japan Steel Works (JSW) has created a worldwide stampede among electricity producers to place orders with the Tokyo-based engineer for nuclear reactor cores - a specialised component in which the company has an effective global monopoly.

As the stakes have risen in the tussle to reach the front of JSW"s order-book queue for reactor cores, energy analysts said that down-payments have soared beyond Ј50 million per unit. In some cases, European and American energy groups are placing huge deposits on equipment that will not be built for another decade.

Nuclear energy experts fear that in its haste to expand production, the nuclear industry may have overlooked this part of the equation, potentially jeopardising the future of the 237 reactors expected by The World Nuclear Association to be built between now and 2030.

The drama surrounding JSW may not end at capacity problems. The company is growing increasingly uneasy that its near-complete dominance of key nuclear componentry makes it a prime takeover target by Russian, Chinese or other buyers. Recently the company has adopted a “poison pill” mechanism that would hugely dilute its shares in the event of a hostile bid.

The bottleneck, which was described to The Times by the managing director of JSW, will not be eased even if the company doubles capacity for large containment vessels. JSW has between 80 to 100 per cent market share for its large reactor components in countries where they are sold. As growing Asian economies rush to meet surging electricity demand and developed nations look to lower their carbon emissions, the worldwide nuclear industry may be forced to redraw its plans.

In response to the looming capacity crisis, other Japanese and South Korean steel companies are examining ways to replicate the JSW production technique, although JSW believes that any company trying to do so would take a minimum of five years.

Czech forges have said that they would be able to retool to build large reactor vessels within about two years.