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At least 19 recordsLinked to original sources
PubMed1989

[Dosimetry of fast neutrons in 1W nuclear reactor with plastic nuclear-track detectors].

A nuclear reactor at Kinki University is operated at the maximum of 1W. It produces fission neutrons as much as gamma-rays. To facilitate its use for neutron radiobiology, fast neutrons inside the reactor were measured with nuclear-track detectors TS 16 N and a pair of ion chambers. The angular dependence of TS 16 N response, an anisotropy of fast neutron fluxes in the reactor and misuse of the kerma factor assumed for radiation protection business are the major causes of discrepancy is measured doses by the two methods. Correction factors for the three causes are proposed. After correction, neutron doses estimated with TS 16 N and chambers agree within 5%. The dose-rate at the reactor's center is about 20 tissue-cGy/h. This is the first in situ dosimetry of fast neutrons in a reactor with track detectors attached to biologic samples. Our routine usage has demonstrated that, if used with caution, TS 16 N elements are handy, reliable monitors for fast neutron dosimetry as they are insensitive to contaminated gamma-rays and small enough to be attached to biologic samples.

Fast Neutrons↗
PubMed1998

Numerical evaluation of the production of radionuclides in a nuclear reactor (Part I).

Numerical evaluation of nuclear transmutations is essential for optimization of radionuclide production. Accordingly, we have developed a generalized computer program called LAURA for predicting the production rates of radionuclides in a nuclear reactor. The program is generalized in the sense that it can be used for calculation of the production rate of any member of a network undergoing spontaneous decay and/or induced neutron transformation in a nuclear reactor. In this paper (Part I), we describe the mathematical basis for the development of LAURA. Expressions based on the Rubinson (1949) approach have been used for the evaluation of the depletion functions. This method is also valid when some of the depletion constants have identical values; thus, the approximate solution of Raykin and Shlyakhter (1989) can be used to account for the effects of feedback due to alpha decay.

Algorithms↗
PubMed2006

Analysis of granular flow in a pebble-bed nuclear reactor.

Pebble-bed nuclear reactor technology, which is currently being revived around the world, raises fundamental questions about dense granular flow in silos. A typical reactor core is composed of graphite fuel pebbles, which drain very slowly in a continuous refueling process. Pebble flow is poorly understood and not easily accessible to experiments, and yet it has a major impact on reactor physics. To address this problem, we perform full-scale, discrete-element simulations in realistic geometries, with up to 440,000 frictional, viscoelastic 6-cm-diam spheres draining in a cylindrical vessel of diameter 3.5m and height 10 m with bottom funnels angled at 30 degrees or 60 degrees. We also simulate a bidisperse core with a dynamic central column of smaller graphite moderator pebbles and show that little mixing occurs down to a 1:2 diameter ratio. We analyze the mean velocity, diffusion and mixing, local ordering and porosity (from Voronoi volumes), the residence-time distribution, and the effects of wall friction and discuss implications for reactor design and the basic physics of granular flow.

Journal Article↗
PubMed1988

Radiation does from medical in-vivo prompt gamma-ray activation using a mobile nuclear reactor.

A method of medical diagnosis of toxic elements, using a neutron beam from a mobile nuclear reactor to perform partial-body in-vivo prompt gamma-ray activation technique, has been developed. Both neutron and gamma-ray dose equivalents in an irradiated phantom and around medical researchers were measured and evaluated. Neutron flux at various kinetic energies was measured using an activation foil technique, and the neutron dose equivalents at tissues of risk inside the irradiated phantom were calculated by neutron transport code. Gamma-ray dose equivalents inside the irradiated phantom and around the nuclear reactor were measured by thermoluminescent dosimeters. The risk associated with the neutron and gamma radiation dose equivalents received by both the irradiated phantom and medical researchers were evaluated in detail. The radiation safety of the in-vivo medical diagnosis using the mobile nuclear reactor, under the context of radiation protection guidelines, is discussed.

Activation Analysis↗
PubMed1985

A feasibility study of the in vivo prompt gamma activation analysis using a mobile nuclear reactor.

A facility for in vivo prompt gamma activation analysis using moderated neutron beams from a 0.1 W mobile nuclear reactor is described. The low-power nuclear reactor provides total neutron flux of 3.3 X 10(4)n cm-2 s-1 on the surface of a vertical beam tube to which a liquid phantom is positioned. The capability of such a partial-body irradiation facility is demonstrated by measuring trace amounts of toxic cadmium in kidney. The detection limit of Cd in kidney for a skin dose of 1.66 mSv (166 mrem) is 1.34 mg under 500 s irradiation. This facility therefore combines the advantages of mobility with high sensitivity of detection of a toxic element under low neutron and gamma doses.

Cadmium Poisoning↗
PubMed2002

Cancer incidence among Finnish nuclear reactor workers.

Because of their well-documented exposures to repeated low doses of ionizing radiation, nuclear reactor workers offer an opportunity to assess cancer risk from low-dose radiation. A cohort of all 15,619 Finnish nuclear reactor workers was established through dose-monitoring records. A questionnaire survey revealed no substantial differences in consumption of tobacco or alcohol between different exposure groups nor between nuclear power company employees and contract workers. In the follow-up for cancer incidence, no clear excess in cancer incidence was observed overall, nor was any observed in any of the specific cancer types studied. There was little evidence for an association between cancer incidence and cumulative radiation dose, but the statistical power was limited. More precise estimates will be available from an international collaborative study of nuclear industry workers, including our cohort.

Adult↗
PubMedDate not supplied

A study of vital rates near a nuclear reactor.

Radiation exposure from the Big Rock Point nuclear reactor in Charlevoix County, Michigan was investigated by studying vital rates for that county and nearby counties in comparison with other matching counties, for periods before and after the reactor began operation. None of the variables studied showed any unusual change in pattern for Charlevoix county after the rector's operation was initiated, but the trend in low-weight births was higher in Charlevoix county than in adjacent counties, whose trends were in turn higher than for the matching counties. However, no other important significant differences were found among those tested statistically, therefore, an examination of these vital rates did not substantiate an association between the proximity of the reactor and the occurrence of pathology. Nevertheless, further study should be conducted to explain the pattern of low-weight births.

Humans↗
PubMed1996

Ion chromatographic determination of transition metals in irradiated nuclear reactor surveillance samples.

The determination of transition metal ions in radioactive (+/-25 microCi/g) low-alloy steels (nuclear reactor surveillance samples) by ion chromatography (IC) is described. The analysis has been done directly without prior separation of the iron matrix. The eluted metal ions have been detected with a UV-visible spectrophotometric detector after post-column complexation with 4-(2-pyridylazo)resorcinol. The results are in a good agreement with the certified values for the standard reference material used. The method was applied to nuclear reactor surveillance samples for the determination of Cu, Mn, Co and Ni.

Journal Article↗
PubMed1987

[Evaluation of the dose equivalent absorbed by the population of Como and surrounding area following the nuclear reactor accident at Chernobyl].

The effects produced as a consequence of the Chernobyl nuclear reactor accident in the population of Como are assessed on the basis of the measurements taken in the environment and on the food. Exposure measurements produced by external radiation and the activities of the different radionuclides introduced into the body, by ingestion and inhalation, made it possible to obtain an estimate of the dose equivalent and its somatic and genetic effects on the population. The results show that such effects may produce 0.5-2 cases of malignant tumour in the next 25 years and 0.2-1 case of genetic damage in the next 60 years and are therefore statistically insignificant.

Accidents↗
PubMed2002

"High specific activity" radiotracers for metallo-toxicological studies: cyclotron and nuclear reactor production, radiochemical separation and "quality control": platinum, iridium, gold, copper and gallium.

Very High Specific Activity RadioNuclides, HSARN, are a powerful tool to label a wide variety of chemical elements and compounds present in the biosphere in ultra-trace amounts. Medium and high Z radionuclides, can be produced by irradiation in light-ions accelerator and sometimes nuclear reactor. If the nuclear reaction product has atomic number different from irradiated target, it is possible separating the radioactive nuclide from irradiated target, without addition of isotopic carrier. These kinds of radionuclides are named No Carrier Added, NCA, and their specific activity is very high and can reach values close to the theoretical Carrier Free one. The true specific activity must be determined by use of very sensitive radioanalytical techniques. If a low isotopic dilution factor is obtained, these radiotracers are used to label inorganic species and complexes of elements, which are presently introduced into the echo-systems by human activities. New production methods for NCA Pt, Ir, Au, Cu and Ga radiotracers are presented, with some details on radiochemistry and quality controls.

Copper↗
PubMed1997

Semen Quality of Workers Exposed to Ionizing Radiation in Decontamination Work after the Chernobyl Nuclear Reactor Accident.

The objective of the study was to assess effects of radiation on sperm quality, including ultramorphology of spermatozoa of men who worked as salvage workers at the Chernobyl nuclear reactor accident site or in the adjacent region. Semen characteristics were assessed by light microscopy, biochemical analysis, and quantitative ultramorphologic analysis seven years after the accident. Samples were collected in the Ukraine, examined there by routine semen analysis, fixed, and transferred to Israel for further examinations. The study population consisted of 18 radiation-exposed individuals. Eighteen unexposed Ukrainian men were examined as controls. Sperm motility was found to be reduced in the radiation-exposed workers. Ultramorphologic defects were evident in the sperm nucleus. Fertility potential was adversely affected among the exposed workers. Thus, salvage workers who had worked at the Chernobyl nuclear reactor accident site or in the vicinity thereof were found to manifest ultramorphologic abnormalities in the sperm nucleus and to have impaired fertility potential seven years after the radiation exposure. The injury was independent of whether the work site had been located at the reactor site or in the vicinity thereof.

Journal Article↗
PubMed2001

Analysis of aerosol distribution inside the object "shelter" at the Chernobyl nuclear reactor site.

Results of the aerosol sampling inside the Object Shelter at the Chornobyl nuclear reactor site are considered in the work. The results show a consistent and significant contribution of submicron fraction to the total aerosol activity. Different methods of interpretation of impactor data series are compared in order to indicate and detect in the most effective way the submicron fraction as a separate component of the distribution. The methods used are as follows-method of probabilistic-logarithmic scale, method of likelihood function, non-linear approximation by sum of several log-normal distributions, and restoration of the initial distribution using passage functions of impactor cascades. Practically all the collected data on aerosol distribution inside the Shelter show a distinct submicron component. The contribution of the submicron component into the total aerosol activity is about 35%. Influence of the actual aerosol distribution on the dose coefficients is analyzed.

Aerosols↗
PubMedDate not supplied

[Microecology of nuclear reactor pool water].

In the course of research it was found that the circulation of pool water through the nuclear reactor core produces a bactericidal effect of microflora due to the influence of radiation of various types. The amount of microbes returns to initial level after 2-4 months after circulation was stopped. Microflora of pool water comprises large amounts of coccus, Gram-positive rods, fungi and a lower content of Gram-negative rods if compared to water which had been used to fill reactor pool. No difference in radioresistance was noticed for unitype microbes isolated from initial water and from reactor pool water. Quality of microflora reflects a unique phenomenon called "selection" which results in vanishing of all the radiosensitive types of microbes and survival of the radioresistant types. Radioresistance grows with increasing of catalase and nuclease activity.

Bacteria↗