Strength of irradiated graphite: a review

Conference · Sun Jul 01 04:00:00 EDT 1979

OSTI ID:6064320

Price, R J

Experimental data on the mechanical strength of nuclear graphite subjected to fast neutron irradiation are reviewed. At fluences below the turnaround point, the mean tensile, flexural, or compressive strength, S, increases over the unirradiated value, S/sub 0/, in a manner related to the irradiation-induced change in Young's modulus, E: S/S/sub 0/ = (E/E/sub 0/)/sup K/. The exponent, k, takes a value between 0.5 and 1, depending on the graphite grade, the irradiation temperature, and the method used for determining E. A value of 0.5 for k would be expected from the Griffith--Irwin theory of fracture if neither the critical flaw size nor the effective surface energy of a crack is altered by irradiation; a value of 1 would be expected if the strain at failure remains constant. At higher fluences, when expansion starts, strength values decrease. The effect of irradiation on the statistical spread of the strength measurements depends on the graphite grade and the neutron fluence. At fluences below the turnaround point, the coefficient of variation of strength determinations for standard reactor grades is little changed, but at higher fluences, and for fine-grained, high strength materials, the coefficient of variation may increase. Although specimens for different locations in a graphite log, or from different logs of the same grade, vary in strength, under the same conditions of irradiation the fractional increase in strength of these specimens will be similar. After irradiation, graphite appears to have a slightly greater resistance to cyclic fatigue, as measured by the homologous stress limits for survival to a specified number of cycles.

• Research Organization: General Atomic Co., San Diego, CA (USA)
• DOE Contract Number: EY-76-C-03-0167
• OSTI ID: 6064320
• Report Number(s): GA-A-15495; CONF-7906105-1
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360603* -- Materials-- Properties
360605 -- Materials-- Radiation Effects
BARYONS
CARBON
COMPRESSION STRENGTH
ELASTICITY
ELEMENTARY PARTICLES
ELEMENTS
FAST NEUTRONS
FERMIONS
FLEXURAL STRENGTH
GRAPHITE
HADRONS
MECHANICAL PROPERTIES
NEUTRONS
NONMETALS
NUCLEONS
PHYSICAL RADIATION EFFECTS
RADIATION EFFECTS
TENSILE PROPERTIES
YOUNG MODULUS