[Assurance of safety and personal protection of the personnel working in conditions of external radiation exposure].

The article contains detailed analysis of current scientific approaches and practical achievements in organizing personal protection of the personnel working in conditions of external radiation exposure and air and surface contamination with radioactive substances. The ways of improvement of personal protection equipment are described. The incorrectness of attempts to create PPE from gamma radiation with the energy of over 0,1 MeV--which are currently quite common--is shown. Today the challenge of creating light PPE from beta radiation and soft photon radiation becomes more urgent due to decreasing the annual equivalent dose of occupational exposure of the crystalline lens from 150 to 20 mSv proposed by IAEA. This requires creation of light and usable protective visors (goggles) from beta radiation and photon radiation with the energy of up to 0,06 MeV.

[Reply to the letter-to-the-editors by V.A. Pitkevich, V.K. Ivanov, S.Iu. Chekin, A.F. Tsyb, "Concerning the problem of radiation exposure levels to the Chernobyl AES accident clean-up participants, included in Russian Medical-Dosimetric State Registry"]. / Otvet na pis'mo v Redaktsiiu V.A. Pitkevicha, V.K. Ivanova, S.Iu. Chekina, A.F. Tsyba "K voprosu o luchevykh nagruzkakh na uchastnikov likvidatsii posledstvii avarii na Chernobyl'skoi AES, zanesennykh v Rossiiskii gosudarstvennyi mediko-dozimetricheskii registr".

Theoretical and practical problems related to the dosimetric data verification for recovery workers at the Chernobyl NPP are considered. The distinctions in definitions epsilon-entropy in paper [1] and delta-entropy in [2] are considered. In a certain measure this distinctions explain distinction in conclusions, made in these papers. Method of dosimetric data collection, used by Institute of Biophysics and its difference from the method of data acquisition, used in national Medical-dosimetric registers is described. Results on determination of a share of participants given for various clean-up worker divisions, contained in pointed delta-shape peaks, received by two various methods, stated in [2] and [6], are compared and their satisfactory conformity with one another is established.

[New standards for radiation safety and effective dose]. / O novykh normakh radiatsionnoi bezopasnosti i éffektivnoi doze.

The scientific bases and the peculiarities of the new radiation safety standards (RSS) implemented in Russia in april 1996 are considered. A comparison is made of the merits and shortcomings of both conceptions of standardization--by means of setting dose limits for the critical organs or by means of limiting the effective dose as a measure of the total radiation risk of late effects. The application of the effective dose to practice gives unquestionable advantages for assessing the sufficiency of arrangements providing radiation safety of personnel or public protection against radiation. However the use of the effective dose for individual dose monitoring is often not good (especially in the case of internal irradiation) due to wide variation caused by oversimplifications in the applied models. Essential shortcomings of the RSS-96 are also the absence of the permissible body burden of radionuclides among the derived standards and the regulation of the mean annual (unmeasurable) values of their concentration in air. It is proposed in addition to the effective dose which limits the risk of stochastic effects to reserve in the RSS the limits of equivalent doses for the main body organs (lungs, liver). This would eliminate the deterministic effects and give the possibility of differential evaluation of the irradiation pattern. It is also proposed to replace the reglamentation of mean annual concentrations of radionuclides in air by the reglamentation of their permissible concentration in the working zone.

[The need to account for beta radiation in determining the total radiation exposure of those working in cleanup]. / O neobkhodimosti ucheta beta-izlucheniia pri opredelenii summarnogo luchevogo vozdeistviia na likvidatorov.

The role of external beta-radiation as one of the major radiation factors effected persons involved in recovery operations (liquidators) after the accident at the Chernobyl nuclear power plant is considered. The paper uses the data of discriminate individual dosimetric monitoring of beta- and gamma-radiation for different groups of liquidators and experimentally received dose distribution in tissue equivalent material in the places of carrying out work. The results obtained by calculation were also used. It was established that experimentally determined ratios of beta-radiation doses to gamma-radiation doses have a good correlation with estimates resulted by calculation. It allowed the authors to use these estimates and individual gamma-radiation dose distribution for drawing histograms of individual beta-radiation dose distribution for open parts of skin, for lens, and gonads in cases of liquidators involved in building "sarcophagus". The obtained estimates of individual doses in the near surface tissue and organs exceeds significantly exposure levels for the whole body. This fact should draw the special attention to the rise in the number of radiation-induced cancer and cataracts.

[The irradiation levels of the participants in the cleanup of the aftermath of the Chernobyl accident in 1986-1987 and the verification of the dosimetric data]. / Urovni oblucheniia uchastnikov likvidatsii posledstvii Chernobyl'skoi avarii v 1986--1987 gg. i verifikatsiia dozimetricheskikh dannykh.

It is considered the organization of individual dosimetric monitoring (IDM) within 30-km zone around Chernobyl nuclear power plant (CNPP) in 1986 for different contingents of recovery workers: the CNPP personnel, Management for Construction 605 (MC-605), military recovery workers, persons assigned to 30-km zone. It is concluded that the quality of IDM had decreased in the following series: the MC-605 personnel, the CNPP personnel, the assigned persons, and military units. The method of dosimetric data verification for recovery workers in 1986 is presented which is based on the analyses of the dependency H(delta)/In delta from delta, where delta is a step of the histogram of distribution, and H(delta) is delta-entropy of distribution. The results obtained by this method correspond to the results of the experts' estimation. It was shown that 60% of registered individual doses for the whole contingent of the recovery workers differ from the real exposure doses. Using the theory of hybrid lognormal distribution it was obtained, in our opinion, real external dose distribution for all the recovery workers. It was estimated that 7% of recovery workers received doses more than 0.25 Gy. Also, the data on values of mean and collective doses for different contingents, as well as for all persons involved in recovery operations is presented.

The dependence of skin lesions on the depth-dose distribution from beta-irradiation of people in the Chernobyl nuclear power plant accident.

A detailed study was made of the conditions of exposure of 56 victims of the Chernobyl accident who suffered radiation lesions in the skin. The most typical conditions were experimentally reconstructed in order to investigate the specific characteristics of the distribution of doses to the skin according to depth for different exposure conditions. The absorbed doses at depths of 7 mg cm-2 and 150 mg cm-2 were calculated on the basis of measurements with multilayer skin dosemeters. The patients were classified into four groups. Dosimetric characteristics for each group were compared with the clinical pictures to establish the critical factors in the occurrence of lesions. It was demonstrated that the depth-dose distribution of beta-radiation to the skin is of great influence not only for the early effects of radiation but also for the later effects. Radiation lesions in the skin led to death if the area of the lesions exceeded about 50% of the total body surface, and if the doses to the skin were about 200-300 Gy at 7 mg cm-2 and more than about 30 Gy at 150 mg cm-2.

[Role of injuries to the vascular plexus in the development of a radiation lesion of the skin in swine]. / Rol' povrezhdeniia sosudistogo spleteniia v razvitii luchevogo porazheniia kozhi svinei.

A single action of beta-radiation of different energy on the swine skin was studied. The analysis and comparison of clinical and histological features of radiation injury to the mode of the absorbed dose formation associated with the depth of location of the skin structural elements permitted to consider deep vascular plexus of the dermis to be the second critical structure (in addition to basal layer of the epidermis) responsible for the radiation reaction development and for the rate and completeness of repair processes, in particular.

[The effect of the size of the irradiation field on the severity and outcome of the radiation injury of swine skin]. / Vliianie razmerov obluchennogo polia na tiazhest' i iskhod luchevogo porazheniia kozhi svinei.

Swine skin areas of 12.56 cm2, 50 cm2 and 100 cm2 were exposed to beta-particles from 90Sr + 90Y (100 Gy). The increase in size of the exposed site caused a considerable increase in the degree of the affection and a change in the regeneration rate. Epithelialization of 12.56 cm2 skin field was completed by the 14th-16th week, and it was absent after 4.5 years in the fields of 50 and 100 cm2.