Pebble-bed nuclear reactors – a safety concern

Experts voice safety concerns about new pebble-bed nuclear reactors Eurekalert, 23 Aug 18

Researchers advise caution as a commercial-scale nuclear reactor known as HTR-PM prepares to become operational in China. The reactor is a pebble-bed, high-temperature gas-cooled reactor (HTGR), a new design that is ostensibly safer but that researchers in the U.S. and Germany warn does not eliminate the possibility of a serious accident. Their commentary, publishing August 23 in the journal Joule, recommends continued research, additional safety measures, and an extended startup phase that would allow for better monitoring.

“There is no reason for any kind of panic, but nuclear technology has risk in any case,” says first author Rainer Moormann, a nuclear safety researcher based in Germany. “A realistic understanding of those risks is essential, especially for operators, and so we urge caution and a spirit of scientific inquiry in the operation of HTR-PM.”

…….the soon-to-be-operational HTR-PM has been built without the safeguards that nuclear reactors in operation today are usually equipped with: it does not have a high-pressure, leak-tight containment structure to serve as a backup in case of an accidental release of radioactive material. It also does not have a redundant active cooling system.

“No reactor is immune to accidents. The absence of core meltdown accidents does not mean that a dangerous event is not possible,” Moormann says. He and his coauthors, Scott Kemp and Ju Li of the Massachusetts Institute of Technology, argue that with new technology, there is always a higher chance of user error. And prototype HTGRs have surprised their operators in the past by forming localized hot spots in the core and unexpectedly high levels of radioactive dust. The pebble-bed design also produces a larger volume of radioactive waste, which is challenging to store or treat……….

Joule, Moormann et al.: “Caution is Necessary in Operating and Managing the Waste of New Pebble-bed Nuclear Reactors” https://www.cell.com/joule/fulltext/S2542-4351(18)30335-0 https://www.eurekalert.org/pub_releases/2018-08/cp-evs081618.php