Hong Kong Regulations

RADIATION (CONTROL OF IRRADIATING APPARATUS) REGULATIONS - REGULATION 19

X-ray tube housing

(1) The protective housing of an X-ray tube shall be so constructed that at
every rating specified by the manufacturer for the tube in that housing the
radiation leakage rate shall not exceed-

   (a)  1 mGy in one hour at a focal distance of 1 m for an X-ray tube used in
        a diagnostic irradiating apparatus;

   (b)  10 mGy in one hour at a focal distance of 1 m, and 300 mGy in one hour
        at 5 cm, from any surface of the housing accessible to the patient for
        an X-ray tube used in therapeutic irradiating apparatus capable of
        operating at voltages up to 500 kV;

   (c)  0.1% of the dose rate of the useful beam at 1 m from the surface of an
        X-ray tube housing used in a therapeutic irradiating  apparatus if the
        tube is capable of operating at voltages above 500 kV.

(2) For the purposes of subregulation (1) measurements may be averaged over an
area of up to 100 cm2 at a distance of 5 cm from the surface of the tube
housing. (13 of 1995 s. 2)

(3) A person who operates or causes to be operated, an X-ray tube which is not
enclosed in a protective housing in accordance with subregulation (1) or (2)
commits an offence and is liable to a fine $15000. (13 of 1995 s. 2) (L.N. 225
of 1990)