Radiostrontium activity concentrations in milk in the republic of Croatia for 1961-2001 and dose assessment.

Results of systematic measurements of 90Sr activity concentrations in milk for the period 1961-2001 are summarized. An exponential decline of radioactivity followed the moratorium on atmospheric nuclear testing. The highest activity of 90Sr deposited by fallout, 1,060 Bq m(-2), was recorded in 1963, while the peak 90Sr activity concentration in milk, 1.42 +/- 0.17 Bq L(-1), was recorded in 1964. The values in year 2001 for fallout deposition and milk were 7.7 Bq m(-2) and 0.07 +/- 0.03 Bq L(-1), respectively. The reactor accident at Chernobyl caused higher 90Sr levels only in 1986. 90Sr fallout activity affects milk activity; the coefficient of correlation between 90Sr fallout activity and 90Sr activity concentrations in milk is 0.80. The transfer coefficient from fallout deposition to milk was estimated to be 2.5 x 10(-3) Bq y L(-1) per Bq m(-2). The dose incurred by milk consumption was estimated for the Croatian population, the annual collective effective dose in 2001 being approximately 2.0 person-Sv.

Iodine prophylaxis and nuclear accidents.

Due to high volatility and environmental mobility, radioactive isotopes of iodine pose a serious risk in the acute phases of a nuclear accident. The critical organ for iodine is the thyroid. A number of studies dealing with thyroid protection from exposure to radioiodine have shown that radioiodine uptake by the thyroid can be effectively blocked by administration of stable iodine, usually in the form of potassium iodide (KI) pills. However, unless perfectly timed, this protective action may be counterproductive. The International Atomic Energy Agency recommends potassium iodide prophylaxis in cases when an avertable thyroid dose by protective action exceeds 100 mGy. This paper reviews experiences and practices with potassium iodide in the thyroid protection. This kind of information should serve as the basis for discussion and decision making on KI prophylactic programmes in nuclear emergency situations in Croatia. If Croatia adopts such programme, it will still have to develop the most effective way of KI stockpiling and distribution or predistribution.

Radioactive contamination of cistern waters along the Croatian coast of the Adriatic sea by 90Sr.

Measurements of radioactive contamination of water samples from cisterns collecting rainwater containing fission products from roofs and other surfaces have been carried out along the Croatian coast of the Adriatic sea since 1968. An exponential decline of radioactivity followed the nuclear moratorium. After the nuclear accident at Chernobyl, higher levels of 137Cs and 90Sr were detected again, with cistern waters being the only environmental samples in Croatia in which elevated 90Sr activities persisted for several years. For the pre-Chernobyl period, the observed mean residence time of 90Sr in cistern waters, estimated to be 6.2 +/- 1.9 y, was similar to that calculated for fallout. Contrary, for the post-Chernobyl time, observed 90Sr mean residence time was calculated to be considerably shorter, reflecting the tropospheric mean residence time. The annual dose for the critical adult population received from 90Sr and 137Cs by drinking cistern water was estimated to be very small, in the 1990's less than few microSv y(-1).

How to use and cite Internet resources, with special attention to radiation protection and health physics WWW sites.

This paper describes an Internet search for the phrases radiation protection and health physics using major search engines and discusses the search procedure and the related problems. Depending on the search engine used, the number of hits ranged from 10,000 to only 17. The author presents some of the most relevant Web sites for radiation protection and health physics, and gives their URLs. As expected, these are mainly the sites of major national and international organizations. The author discusses a model for citation of WWW resources and refers to Internet links where this issue has been elaborated in more detail. Numerous links to various institutions and Web resources are given as well.

Radiotoxicity of tritiated water and tritiated hydrogen.

Tritium in the form of tritiated water is much more radiotoxic than tritiated hydrogen. The effective dose which results from tritiated water as the oxidation product of Inhaled tritiated hydrogen gas makes about 55 per cent of the effective dose due to direct irradiation of the lungs by tritiated hydrogen only. The inclusion of the dose due to the production of tritiated water would tower the relative toxicity ratio as well as the value of derived air concentration for tritiated hydrogen. Therefore, to assess the health hazard from tritium exposure, for the two species the relative significance of 1:12,000 should be used, instead of the relative radiotoxicity ratio of 1:25,000 as given by the International Commission on Radiological Protection.

Radiation doses due to human exposure to cosmic radiation in the Republic of Croatia.

The annual per caput whole body equivalent dose for the world's population on ground level in areas on normal background from natural sources of radiation is approximately 2.4 mSv, 0.3 mSv of which is due to cosmic rays. As the intensity of cosmic radiation increases with altitude, the subpopulation of aircraft flight crews and frequent flyers may receive an additional equivalent dose of up to 1 mSv during commercial flights. The estimated annual collective equivalent dose from aircraft flights for the Republic of Croatia is about 4 man Sv, whereas the annual collective effective dose due to the cosmic radiation component of normal background radiation is approximately 1200 man Sv. Future development of hypersonic aircraft, which would fly orbital trajectories above the Earth's atmosphere would cause a significant increase of doses. Also, future utilization of extended space missions might be limited by high equivalent doses to space travellers.

Radiocaesium activities in wheat in Croatia.

Results of systematic, long-term measurements of 137Cs activities in wheat are summarized. 137Cs fallout activity affected wheat activity the coefficient of correlation being 0.91. A model used by UNSCEAR was used to describe 137Cs transfer from fallout deposition to wheat. The transfer coefficient was calculated to be 6.1 x 10(-3) Bq yr kg-1/(Bq m-2). The dose incurred by wheat consumption was estimated for the Croatian population, the annual collective equivalent dose being approximately 550 man Sv for the 1965-1992 period. After the Chernobyl nuclear accident the 134Cs: 137Cs activity ratio in wheat was approximately 0.5, and did not differ from that for other environmental samples.

[Equivalent dose or dose equivalence?]. / Ekvivalentna doza ili dozni ekvivalent?

In the Croatian language the terms denoting certain physical quantities in the field of radiation protection dosimetry lack precision. Consequently, either the English expressions or mathematical formulas are used instead. The situation is even worse as only a limited number of textbooks, reference books and professional papers are available in the Croatian language. This paper reviews dosimetric quantities and their definitions, and sets forth a survey of the radiation dosimetry terms in literature. The terminology is both non-uniform and imprecise, especially since the latest recommendations of the International Commission on Radiological Protection (ICRP) have introduced new concepts of some dosimetric quantities. Also, Croatian terms for certain dosimetric quantities still have not been fully accepted. Bearing in mind the need for clear and well defined technical terms the author proposes Croatian terms for several dosimetric quantities.

90Sr and 137Cs in pilchards from the Adriatic Sea.

The biological concentration factors for the system pilchard/sea-water for 90Sr and 137Cs are presented and discussed. The 90Sr concentration factor was constant, whereas the concentration factor for 137Cs steadily increased after the Chernobyl accident. An UNSCEAR model was used to describe 90Sr transfer from fallout deposition to pilchards. The transfer coefficient was calculated to be 1.85 x 10(-3) Bq yr kg-1/(Bq m-2). The dose incurred by pilchard consumption was estimated for the Croatian population, the annual collective equivalent dose being less than 0.1 Sv.

[Protection of the Croatian population from accidental radioactive contamination of the food chain]. / Zastita stanovnistva republike Hrvatske od akcidentalne radioaktivne kontaminacije prehrambenog lanca.

The paper indicates the importance of investigating radionuclide translocation in the human food chain, and the contribution of selected food components in total exposure of the population after accidental radioactive contamination. Data on radioactive contamination and risk assessment of the Croatian population after the Chernobyl nuclear accident are given and possibilities of decontamination of food chain components are discussed. Literature data on radionuclide removal from the human food chain are compared to the results of own investigations. Emphasis is placed on biologically most important radionuclides, 131I, 90Sr, 137Cs, and the most effective means of protection are sought. The preventive measures following a nuclear accident should be based on the cost-benefit principle i.e. the damage from applying radiation protection measures should not exceed the benefit from possible dose reduction.

Radioactive contamination of the Adriatic Sea by 90Sr and 137Cs.

Results of systematic long-term measurements of 90Sr and 137Cs in surface seawater, performed at four locations along the Croatian coast of the Adriatic Sea, are summarized. Observed trends in annual mean activity concentrations are discussed. 90Sr and 137Cs fallout activities affect seawater activity, the coefficient of correlation between 90Sr fallout activity and 90Sr seawater activity being 0.72. No significant variations of 90Sr mean residence time in the sea-mixed layer on different locations were found. From 1978-1985, the 137Cs:90Sr activity ratio in seawater was 1.52 +/- 0.40. In May 1986, as the consequence of the Chernobyl nuclear accident, this radio increased to 92.4 +/- 58.2.

[Radioactive contamination of cistern waters along the Croatian coast of the Adriatic Sea]. / Radioaktivna kontaminacija cisternskih voda duz hrvatske obale Jadranskog mora.

Measurements of radioactive contamination of cistern waters with 90Sr, 134Cs and 137Cs have been carried out along the Croatian coast of the Adriatic Sea. An exponential decline of radioactivity followed the moratorium on nuclear tests. After the nuclear accident at Chernobyl, high radioactivity levels were detected again. The pre-Chernobyl and the post-Chernobyl mean residence times of 90Sr in cistern waters reflect the mechanism by which strontium was released to the atmosphere (atmospheric nuclear weapon tests conducted in the stratosphere or explosions in the Chernobyl nuclear reactor releasing radioactive material to the troposphere). For the pre-Chernobyl period, the mean residence time of 90Sr in cistern waters was similar to that calculated for fallout, being approximately 10 years. The post-Chernobyl 137Cs/90Sr activity ratio has been decreasing, but it has not yet reached the pre-Chernobyl values (approximately 1.6). The time-dependent 134Cs/137Cs activity ratio reflects the Chernobyl reactor inventory of these radionuclides. The annual dose for the critical adult population received from 90Sr, 134Cs and 137Cs by consumption of cistern water was estimated to be a few percentages of the dose from natural background radiation.

[Estimation of the energy fraction emitted by alpha particles in the mineralized part of trabecular bone which is absorbed in the bone marrow]. / Procjena frakcije energije alfa cestica emitiranih iz mineralnog dijela trabekularne kosti, apsorbirane u kostanoj mozdini.

The cells at particular carcinogenic risk in the skeleton are haematopoietic stem cells of the marrow, which are predominantly distributed throughout the haematopoietic marrow within the trabecular bone. The Monte Carlo method for estimating the fraction of the energy of alpha particles emitted in a volume of the mineral part of the bone which is deposited in the marrow is described. The relationship between the absorbed fraction (AF) of the alpha particles and their energy was found to be linear. AF (Red Marrow----Trabecular Bone) is calculated to be 0.016 for the radionuclides emitting 3 MeV alpha particles and 0.080 for those emitting 8 MeV alpha particles. As radionuclides are for purposes of bone dosimetry dichotomously classified as surface and volume seekers, the estimation of energy deposition in the skeletal target organs can be highly dependent on this classification because of complicated geometric relationships between the source and target regions.