Australian news, and some related international items

NuScam’s not so small nuclear reactors need $1.4 billion subsidy, and might not be so safe

Smaller, cheaper [?] reactor aims to revive nuclear industry, but design problems raise safety concerns, Science, By Adrian Cho, Aug. 18, 2020  Engineers at NuScale Power believe they can revive the moribund U.S. nuclear industry by thinking small. Spun out of Oregon State University in 2007, the company is striving to win approval from the U.S. Nuclear Regulatory Commission (NRC) for the design of a new factory-built, modular fission reactor meant to be smaller, safer, and cheaper than the gigawatt behemoths operating today. But even as that 4-year process culminates, reviewers have unearthed design problems, including one that critics say undermines NuScale’s claim that in an emergency, its small modular reactor (SMR) would shut itself down without operator intervention.The issues are typical of the snags new reactor designs run into on the road to approval, says Michael Corradini, a nuclear engineer at the University of Wisconsin, Madison. “I don’t think these things are show-stoppers.” However, M. V. Ramana, a physicist who studies public policy at the University of British Columbia, Vancouver, and has been critical of NuScale, says the problems show the company has oversold the claim that its SMRs are “walk-away safe.” “They have given you the standard by which to evaluate them and they’re failing,” Ramana says.

Passive safety?

Normally, convection circulates water—laced with boron to tune the nuclear reaction—through the core of NuScale’s reactor (left). If the reactor overheats, it shuts down and valves release steam into the containment vessel, where it conducts heat to a surrounding pool and condenses (center). The water flows back into the core, keeping it safely submerged (right). But the condensed water can be low in boron, and reviewers worried it could cause the reactor to spring back to life………..

NuScale’s likely first customer, Utah Associated Municipal Power Systems (UAMPS), has delayed plans to build a NuScale plant, which would include a dozen of the reactors, at the Department of Energy’s (DOE’s) Idaho National Laboratory. The $6.1 billion plant would now be completed by 2030, 3 years later than previously planned, says UAMPS spokesperson LaVarr Webb. ………        The delay will give UAMPS more time to develop its application for an NRC license to build and operate the plant, Webb says. The deal depends on DOE contributing $1.4 billion to the cost of the plant, he adds. 

………  A NuScale reactor—which would be less than 25 meters high, hold about one-eighth as much fuel as a large power reactor, and generate less than one-tenth as much electric power—would rely on natural convection to circulate the water

……….. In March, however, a panel of independent experts found a potential flaw in that scheme. To help control the chain reaction, the reactor’s cooling water contains boron, which, unlike water, absorbs neutrons. But the steam leaves the boron behind, so the element will be missing from the water condensing in the reactor and containment vessel, the NRC’s Advisory Committee on Reactor Safeguards (ACRS) noted. When the boron-poor water re-enters the core, it could conceivably revive the chain reaction and possibly melt the core, ACRS concluded in a report on its 5–6 March meeting.

August 20, 2020 - Posted by | General News

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