Speakers
Description
Efforts are underway to develop nuclear fusion reactors for power production that have improved safety and efficiency. Existing reactor designs that rely on solid blanket breeder materials could potentially lead to failure situations. As such, there is growing interest in using liquid blanket breeder materials to extract heat generated by the reactor to use it to cool the reactor and to produce power and tritium. Among the available liquid breeder materials, molten salts made from lithium (Li), fluorine (F), and beryllium (Be) such as 2LiF-BeF2 or “FLiBe” has attractive properties for this application. The purposes of this presentation are: 1) review available data on the properties of FLiBe, 2) describe potential for adverse health effects from exposure, and 3) discuss how past experiences with beryllium can inform future efforts to protect nuclear workers from exposure to FLiBe.
A literature search of the Scopus database was conducted to identify relevant publications on safety and health aspects of FLiBe. No original data specific to health-related properties and adverse health effects of FLiBe was identified by the search. Therefore, we summarized what is known about BeF2 by itself.
Properties of BeF2: One study characterized the physicochemical properties of aerosol collected from a fluoride furnace used to make BeF2, an intermediary in primary production of beryllium metal powder. The aerosol particles were mainly amorphous, though crystalline phases were present, including beryllium oxide and ammonium fluoride. Analysis of individual particles identified F and oxygen. Bulk analysis determined that the aerosol particles contained 1.5 – 3.5% beryllium by mass. It was unknown if BeF2 was present in an amorphous form in the particles.
Potential for adverse health effects: An epidemiological study identified elevated process related risk of chronic beryllium disease (CBD) among employees who worked at the fluoride furnace. Based on the particle physicochemical characterization data, it was postulated that dissociation of F from fluoride furnace particles that deposit in the lung could form acids that induce inflammation, thereby providing an environment conducive to adverse effects from the beryllium component of the particles. In the 1950s, it was shown that skin patch testing with BeF2 had higher capacity to induce beryllium sensitization (BeS) and caused a more vigorous positive skin reaction than other beryllium salts that contained the same amount of beryllium. Epidemiological evidence indicates that beryllium salts were significantly associated with skin symptoms and BeS in primary production workers.
Past experiences/future efforts: To our knowledge, there is no data available on the physicochemical properties and health risks of FLiBe. However, available historical evidence indicated that inhalation and skin exposure to particles generated at a fluoride furnace imparted elevated risk of BeS and CBD and that patch testing with BeF2 can induce BeS. Given the known toxicity of these process intermediary particles and BeF2 salt, several precautionary measures can be considered to mitigate exposures to FLiBe until there is understanding of its specific toxicity, exposure, and risk. Examples of such measures include 1) utilizing concepts of prevention-through-design when constructing reactors to engineer out exposure scenarios, 2) installing effective ventilation to remove airborne particles from workplace atmospheres and to reduce their settling onto surfaces that can be contacted by skin, and 3) implementing controls to prevent inhalation and skin contact with FLiBe.