KU1 quartz glass, a radiation-resistant material, is being considered for use in different fusion applications such as remote handling optical transmission components and diagnostic windows. Gamma ( 60Co) and 1.8 MeV electron irradiations have been carried out to study the ionizing radiation-induced optical absorption in this material. The results show that while the optical absorption induced by irradiation in the KU1 silica is acceptable for the remote handling optical transmission components, this is not the case with diagnostic window applications, where background absorption may pose a problem for LIDAR. However, this disadvantage may be minimised by pre-irradiation at about 200°C.