Antinuclear

Dozens of US nuclear power plants at risk due to climate change: Moody’s, S and P Global, Author Steven Dolley     Washington Editor,  Keiron Greenhalgh 19 Aug 20

37 GW of nuclear capacity at risk from flooding

48 GW at risk from heat, water stress

Merchant plants have fewer options to recover mitigation costs

Washington — Dozens of US nuclear power plants, comprising nearly half the country’s operational nuclear generating capacity, “will face growing credit risks” in the next 10 to 20 years due to flooding, hurricanes, heat stress and other predicted impacts of climate change, Moody’s Investors Service said in a report Aug. 18.

“The consequences of climate change can affect every aspect of nuclear plant operations – from fuel handling and power and steam generation to maintenance, safety systems and waste processing,” the report said, noting that “the severity of these risks will vary by region, with the ultimate credit impact depending on the ability of plant operators to invest in mitigating measures to manage these risks.”

Moody’s did not specify mitigation measures that are being, or should be, taken.

Water cooling needs expose plants to the risk of flooding, sea-level rise and hurricanes, and “about 37 gigawatts (GW) of US nuclear capacity [have] elevated exposure to flood risk,” Moody’s said.

Also, the report noted, “rising heat and water stress can have an adverse impact on plant operations,” with “about 48 GW of nuclear capacity [having] elevated exposure to combined rising heat and water stress.”

“Regulated or cost-based nuclear plants,” comprising about 55 GW of capacity in the US, “face elevated heat and water stress across most locations, with moderate to high risk of floods, hurricanes, and sea level rise for certain coastal plants,” Moody’s said. However, it added: “The credit impact of these climate risks is likely to be more modest for operators of these nuclear plants, relative to market-based plants, because they have the ability to recoup costs through rate recovery mechanisms.”

By contrast, “market-based plants,” with a total of about 44 GW of capacity, “face elevated heat stress and more water stress than regulated/cost-based plants, with fewer plants at risk of floods and hurricanes,” it said.

The highest risk, or “red flag,” category includes plants that are “highly exposed to historical and/or projected risks, indicating high potential for negative impacts,” Moody’s said.

According to the report, five plants with a combined capacity of about 9.1 GW are in the red flag category for floods. Some 13 plants with a combined capacity of about 23.8 GW were found to be at red-flag risk for heat stress. The categories of hurricanes, sea level rise and water stress each had one plant expected to be at red-flag risk.

Because some US nuclear units “are seeking to extend their operations by 20, or even 40 years,” Moody’s said, “operators will have to consider these risks when implementing resilience measures.”………. https://www.spglobal.com/platts/en/market-insights/latest-news/electric-power/081820-dozens-of-us-nuclear-power-plants-at-risk-due-to-climate-change-moodys

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.https://www.sciencemag.org/news/2020/08/smaller-cheaper-reactor-aims-revive-nuclear-industry-design-problems-raise-safety