A radiation protection operational quantity that is isotropic and can be measured

A new operational quantity is suggested, H0(d), that is the dose equivalent in the cavity of a hollow sphere of the same composition and external diameter as the ICRU sphere. The parameter d corresponds to the wall thickness of such a hollow phantom, d=25 mm being its recommended value for environmental monitoring of penetrating radiations. The proposed quantity is invariant to the direction of incident radiation. Its relation to the effective dose equivalent is not less advantageous than that of the ambient dose equivalent. The feasibility of the experimental realisation of H0(25) has been demonstrated. (author)