defectoscopy, professional harm

From Big Medical Encyclopedia

DEFECTOSCOPY, professional harm (Latin defectus a shortcoming + grech, skopeo to consider, investigate) — a complex of control methods of materials and products without their destruction for the purpose of detection of defects which can be revealed by means of magnetic and electric fields, radio waves, ultrasonic fluctuations, x-ray and gamma-rays.

Control of products from ferromagnetic materials is exercised magnetic by D. Indikator magnetic powder (ferriferrous oxide) or its suspension serves. The ferroprobe magnetic method allows to automate control and grading. During the performance of operations it is necessary to provide protection of personnel against influence of magnetic field.

Radio wave D. is based on use of microwaves santi-and millimetric range. A source is the generator; radio waves via ruporny antennas get into a product, signals are registered the receiving device. An adverse factor for working is microwave radiation (see. Electromagnetic field ). It is necessary to exercise control of a radiation intensity and to use the general and individual means of protection.

Ultrasonic D. uses elastic vibrations of ultrasonic range by change of parameters of frequencies, type of waves, the modes of radiation and other parameters. Registration is made on the screen of an oscilloscope or self-recording devices. During the work it is necessary to prevent impact on an organism of ultrasonic fluctuations (see. Ultrasound ).

X-ray defectoscopy and gamma-radiography are based on absorption of beams at their passing through metals. Intensity of beams is registered photographic (on a film) or ionization by methods. The last method is more preferable in a gigabyte. relation: time for registration is reduced, radiation of personnel decreases, control in line system of production is possible. These methods D., and especially control by gamma-rays, have the most wide spread occurance. For X-ray defectoscopy X-ray equipments with a radiation energy from 5 to 400 kev are used. Control of products is exercised in stationary conditions.

A harmful factor is radiation of personnel X-ray. Apply radioisotopes to gamma-radiography ( 60 Co, 134 Cs, 192 Ir, etc.) which conclude in tight metal covers. Use drugs activity from 0,2 to 100 and more than a g-ekv of Ra; sources place in figurative protective containers or special installations.

The major harmful factor is external general or local irradiation of personnel which is possible during the transportation of a source, its installation to the initial position, raying; danger of radiation increases during the work with the sources which are in figurative containers on big exposures of raying, at control in hard-to-reach spots, during repair and a recharge. At D. by means of special gamma-ray irradiation plants, napr, industrial GUP-So-50 where distance steering, radiation insignificant is provided. At gross violation of rules of work with sources perhaps intensive radiation with the subsequent development radial illness (see).

The persons occupied with D. are provided with individual dosimeters. A marginal annual whole-body dose — 5r, a dose of local radiation (brushes, a forearm, feet) — 75 rubles. Performing preliminary and periodic medical examinations is obligatory. All working shall be trained in safe methods of work and know instructions for use defensors (see. Antiactinic protection ).

Bibliography: A. N. majors, etc. Radio isotope defectoscopy, M., 1976; Tarasenko N. Yu. Occupational health at gamma-radiography of metal products, M., 1960.

N. Yu. Tarasenko.