rayon cosmique primaire lourd

OBS: rayon cosmique primaire lourd : terme habituellement utilisé au pluriel.

CONT: However, the small percentage of cosmic rays that are heavy primaries do pose a serious risk even over a period of time as short as months, or perhaps weeks ... As a result, for a mission of more than a few hours to be reasonably safe there is no escaping the need for some sort of radiation shielding.
OBS: heavy primary: term normaly used in the plural.