Helium induced swelling and tritium trapping mechanisms in irradiated beryllium: A comprehensive approach

Conference · Sat Dec 31 04:00:00 EST 1994

OSTI ID:197096

Scaffidi-Argentina, F; Dalle Donne, M ^[1]; Ferrero, C ^[2]

---

1. Institut fur Neutronenphysik und Reaktortechnik, Karlsruhe (Germany)
2. European Synchrotron Radiation Facility, Grenoble (France); and others

Since beryllium is considered as one of the best neutron multipliers for the blanket of a fusion reactor, several studies have been initiated to evaluate this material behavior under irradiation both for typical operating and accidental conditions. The most important effects of radiation damage in beryllium are swelling, embrittlement and tritium retention. The helium produced mainly by the reaction {sup 9}Be(n,2n)2 {sup 4}He is the dominant cause of beryllium swelling which represents the major lifetime limiting factor for the material. Furthermore, the tritium inventory in beryllium, produced by simultaneous transmutation reactions, constitutes a safety hazard in case of accidental temperature excursions in the reactor. The helium bubbles and the oxygen impurities present in the material appear to be the main causes of tritium retention in irradiated beryllium. In order to predict the performance of beryllium in the blanket up to high neutron fluences, due to the strong relation between helium bubbles distribution and tritium release, it is necessary to evaluate helium and tritium transport processes by using a comprehensive model. The kinetics and dynamics of helium and tritium in beryllium and the dynamics of the material expansion have been described by a system of coupled reaction-rate differential equations. The relevant effects occurring in irradiated beryllium under steady or transient temperature conditions have been considered from a microscopic (lattice and subgranular volume elements), structural (metallographic features of the material) and geometrical (specimen design parameters) point of view. A new model describing the trapping effects on tritium due to chemical reactions with beryllium oxide and capture in helium bubbles has been included in the code.

• OSTI ID: 197096
• Report Number(s): CONF-940664--
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
BERYLLIUM
BREEDING BLANKETS
HELIUM EMBRITTLEMENT
INTERSTITIAL HELIUM GENERATION
PHYSICAL RADIATION EFFECTS
SAFETY ANALYSIS
SWELLING
TEMPERATURE DISTRIBUTION
TRANSIENTS
TRAPPING
TRITIUM