The disks of Nd:doped phosphate glass in the amplifiers of the Nova laser contain platinum particles with sizes ranging from <5 ..mu..m (detection limit) to about 100 ..mu..m. The particle density varies from about 0.01 to 1.0 cm/sup -3/. These particles cause fractures when irradiated at fluences >2.5 J/cm/sup 2/ delivered in 1-ns, 1054-nm pulses. Under repeated irradiation at 5 to 7 J/cm/sup 2/, damage from small (<5 ..mu..m) particles asymptotically approaches a limiting size, but damage surrounding the larger particles grows steadily. The damage threshold fluence, 2.5 J/cm/sup 2/, corresponds to operation of Nova at one-half the desired output for pulse durations longer than 1 nsec. Operation at higher fluences causes accumulation of damage in the output amplifiers and requires replacement of the disks in those amplifiers on an accelerated schedule. 9 refs., 5 figs.