Characterization of Geiger-Müller radiation detectors response at the University of Costa Rica's Cyclotron Facilities / Caracterización de la respuesta de detectores de radiación Geiger-Müller en el Ciclotrón de la Universidad de Costa Rica

To ensure a reliable verification of a radiation detector, the right parameters for this response verification must be determined and a specific characterization on the detectors of interest must be performed. These were the main pillars of this study, where four Geiger-Müller at the University of Costa Rica's Cyclotron Facilities' main laboratories were studied and characterized using a 137Cs source. First, a verification of the inverse-square law was performed to corroborate the correct measurement by the detectors as the distance from a 137Cs source to the detectors was varied using a new design for a positioner support to ensure repeatability. This verification yielded a potential fit curve with and equation D=670635 x-1.961 (error percentage of 1.95%) and an R2 value of 0.9836. Then, using combinations of copper plates of widths 1.0 mm and 2.0 mm as attenuators between the source and the detectors, the mass attenuation coefficient for copper was obtained only as a reference value for future calibrations of the detectors. The result for this value was 0.040 cm2 /g. The results obtained in this study and the method developed to achieve these results will serve as a base for calibrations of the detectors at these facilities, which will ensure the safety of the patients and personnel in this building.

Para asegurar respuesta correcta de un detector de radiación, se deben determinar los parámetros correctos para esta verificación y debe realizarse una caracterización específica de los detectores de interés. Estos fueron los pilares principales de este estudio, donde se estudiaron y caracterizaron 4 detectores Geiger-Müller en los laboratorios principales del Ciclotrón de la Universidad de Costa Rica utilizando una fuente radiactiva de 137Cs. Primero, se realizó una verificación de la ley del inverso-cuadrado para corroborar la medición correcta de los detectores según se varía la distancia entre la fuente de 137Cs al detector utilizando un diseño nuevo de un soporte posicionador para la fuente que asegura la repetibilidad entre experimentos. Esta verificación resultó en una curva de ajuste potencial de ecuación D=670635x-1,961 (porcentaje de error de 1,95%) y un valor de R2 de 0,9836. Luego, utilizando combinaciones de placas de cobre de espesores 1,0 mm y 2,0 mm como atenuadores entre la fuente y los detectores, se obtuvo el coeficiente de atenuación másico para el cobre como un valor de referencia para futuras calibraciones de los detectores. Este resultado fue de 0,040 cm2/g. Los resultados obtenidos en esta investigación y el método desarrollado para lograr estos resultados servirán como una base para una futura confirmación metrológica calibraciones de los detectores en estos laboratorios, lo cual colaborará con la seguridad y protección radiológica de pacientes y trabajadores en este edificio.

Cancer incidence in the cohort exposed to Cesium-137 accident in Goiânia (Brazil) in 1987

Objective:to describe the incidence of cancer cases in the direct victims of the accident, Groups I and II, and compare with overall cancer incidence rates for the population of Goiânia. Method: A descriptive study is presented herein, on the cohort of patients directly exposed and contaminated (Groups I and II) during the cesium-137 accident, which occurred in Goiania (Midwest Brazil) in 1987. The incident cases of malignant neoplasms diagnosed between 1988 and 2017 are described. Analysis included calculation of the Incidence Rate Ratio (IRR) with 95% confidence intervals (CI95%), according to gender. Results: In the 30-year period (1987-2017) following individual exposure, there were seven cancer cases in six directly exposed victims of the cesium-137 accident. Of these, five neoplasms occurred in men, in the esophagus (1), prostrate (3), bladder (1), and two in women, involving breast cancer (1) and skin melanoma (1). The accumulated incidence rates in the direct victims of the Cesium-137 accident were 327.9/100,000 for men and 148.6/100,000 for women. For the overall population of Goiânia, rates were 221.4/100,000 and 231.2/100,000 in men and women, respectively. The ratios of brute incidence rates (direct victims of Cesium-137/population of Goiânia) were 1.5 (IC95%:0.4;5.9) in men and 0.6 (IC95%:0.1;3.8) in women, with no statistically significant differences. Conclusion: Cancer incidence in the direct victims of the Cesium-137 accident (Groups I and II), according to sex, was not different from the incidence in those not exposed to Cesium-137 in the municipality of Goiânia. Cancer risk was similar to that of the general population of the municipality of Goiânia

Objetivo: descrever a incidência de casos de câncer nas vítimas diretas do acidente Grupo I e II e comparar com as taxas de incidência de câncer na população de Goiânia. Método: Estudo descritivo da coorte de pacientes diretamente expostos e contaminados (Grupos I e II), no acidente com Césio 137, ocorrido em Goiânia (Brasil), em 1987. Descrevemos os casos incidentes de neoplasia maligna diagnosticados no período entre 1988 e 2017. Foram calculados a razão das taxas de incidência e os intervalos de confiança de 95% (IC95%), segundo o sexo na população de estudo. Resultados: No período de 30 anos (1987-2017), ocorreram sete casos de câncer, em seis vítimas diretas do acidente pelo césio-137. Desses, cinco ocorreram em homens (esôfago [1], próstata [3] e bexiga [1]) e dois, em mulheres (mama [1] e melanoma da pele [1]). As taxas de incidência acumulada nas vítimas diretas do Césio-137 foram de 327,9/100,000 entre homens e de 148,6/100,000 entre as mulheres. Na população de Goiânia, as taxas foram de 221,4/100,000 e 231,2/100,000 em homens e mulheres, respectivamente. As razões das taxas de incidência bruta (vítimas diretas do Césio-137/população de Goiânia) foram 1,5 (IC95%:0,4;5,9) em homens e 0,6 (IC95%:0,1;3,8) em mulheres, não houve diferenças estatisticamente significativas. Conclusão: A incidência de câncer nas vítimas diretas do acidente pelo Césio 137 (Grupos I e II), segundo o sexo, não foi diferente da população não exposta ao Césio-137 do município de Goiânia; portanto, o risco de câncer foi semelhante ao da população geral do Município de Goiânia.

20 años de investigaciones y aplicaciones en Cuba de los radiotrazadores y el perfilaje en la industria y el medioambiente / 20 years of Cuban radiotracer and scanning researches and applications at the industry and the environment

Las tecnologías de radiotrazadores y de escaneo son herramientas bien consolidadas para el estudio, análisis y evaluación de los procesos industriales y medioambientales. En este trabajo se sintetizan los principales resultados alcanzados por el Grupo de Aplicaciones Industriales y Medioambientales de los Radiotrazadores en el Departamento de Radioquímica. La tecnología de radiotrazadores se ha empleado con éxito para la caracterización del mezclado en reactores discontinuos, los estudios sobre el comportamiento del 99mTc en aguas naturales y residuales, la calibración y validación del modelo de calidad de agua del río Almendares, la caracterización de un reactor anaerobio para el tratamiento de los residuales en el CAI “Pablo Noriega”, la verificación y validación del modelo DFC en un cristalizador azucarero, el desarrollo de un generador radisotópico de ? / ?, la modelación de la calidad del agua en el segmento medio del río Luyanó, y para la modelación de la calidad del agua en el río Guaire, Caracas, Venezuela. En los últimos años el grupo ha desarrollado y evaluado a nivel de laboratorio radiotrazadores para fluidos orgánicos, particularmente relacionados con la industria del petróleo y para sólidos, empleando como precursor al ?. Mientras la técnica de escaneo se ha utilizado para el perfilaje gamma en torres de destilación de alcohol de los CAI "Héctor Molina”“Heriberto Duquesne" y "Jesús Rabí".

Assessment of radiation exposure from cesium-137 contaminated roads for epidemiological studies in Seoul, Korea

OBJECTIVES: We aimed to assess the radiation exposure for epidemiologic investigation in residents exposed to radiation from roads that were accidentally found to be contaminated with radioactive cesium-137 (137Cs) in Seoul. METHODS: Using information regarding the frequency and duration of passing via the 137Cs contaminated roads or residing/working near the roads from the questionnaires that were obtained from 8875 residents and the measured radiation doses reported by the Nuclear Safety and Security Commission, we calculated the total cumulative dose of radiation exposure for each person. RESULTS: Sixty-three percent of the residents who responded to the questionnaire were considered as ever-exposed and 1% of them had a total cumulative dose of more than 10 mSv. The mean (minimum, maximum) duration of radiation exposure was 4.75 years (0.08, 11.98) and the geometric mean (minimum, maximum) of the total cumulative dose was 0.049 mSv (<0.001, 35.35) in the exposed. CONCLUSIONS: An individual exposure assessment was performed for an epidemiological study to estimate the health risk among residents living in the vicinity of 137Cs contaminated roads. The average exposure dose in the exposed people was less than 5% of the current guideline.

Assessment of radiation exposure from cesium-137 contaminated roads for epidemiological studies in Seoul, Korea

OBJECTIVES: We aimed to assess the radiation exposure for epidemiologic investigation in residents exposed to radiation from roads that were accidentally found to be contaminated with radioactive cesium-137 (137Cs) in Seoul. METHODS: Using information regarding the frequency and duration of passing via the 137Cs contaminated roads or residing/working near the roads from the questionnaires that were obtained from 8875 residents and the measured radiation doses reported by the Nuclear Safety and Security Commission, we calculated the total cumulative dose of radiation exposure for each person. RESULTS: Sixty-three percent of the residents who responded to the questionnaire were considered as ever-exposed and 1% of them had a total cumulative dose of more than 10 mSv. The mean (minimum, maximum) duration of radiation exposure was 4.75 years (0.08, 11.98) and the geometric mean (minimum, maximum) of the total cumulative dose was 0.049 mSv (<0.001, 35.35) in the exposed. CONCLUSIONS: An individual exposure assessment was performed for an epidemiological study to estimate the health risk among residents living in the vicinity of 137Cs contaminated roads. The average exposure dose in the exposed people was less than 5% of the current guideline.

Evaluation of a novel decorporation approach to prevent radioactivity uptake by using acidosis in experimental animals.

With an aim to devise a prophylactic and/or therapeutic approach for preventing internalization of radiothallium (201Tl), and more importantly by implication, its chemical analogue radiocesium (137Cs) during any nuclear emergency, different ex vivo and in vivo animal models were created to determine the role of pH in absorption of 201Tl across jejunum/muscle tissue and whole body retention of 201Tl respectively. Movement of Tl+ under simulated pH conditions proved that pH had direct influence on its absorption. Oral intake of acidified water or parenteral administration of lactic acid was able to reduce the body burden of 201Tl by up to 12 and 50% respectively. The results indicate that acidification of gut, within physiological range may be used as an option for decorporation/inhibition of incorporation of radiothallium and radiocesium, particularly in cases of mass casualty.

Inventario de referencia de para estudios de erosión de los suelos en la provincia de Cienfuegos, Cuba / reference inventory for the soils erosion studies in Cienfuegos, Cuba

Para la aplicación exitosa de la técnica del en estudios de erosión del suelo es necesario establecer correctamente el inventario de referencia que representa la entrada total de este radionúclido a la superficie terrestre. En tal sentido, se selecciona un sitio que no haya sido perturbado ni por la erosión ni por el depósito, reconocido como sitio de referencia. En la práctica encontrar estos sitios suele ser difícil. El objetivo de esta investigación fue establecer el inventario de referencia de para localidades de la provincia de Cienfuegos. Quedó establecido que el intervalo de confianza del inventario de referencia de es [1082; 1266] , con una confiabilidad del 90% y el coeficiente de variación del inventario de referencia en las localidades investigadas fue de 11%. Estos valores están en correspondencia con los reportados por otros autores para sitios similares. Asimismo, se determinó la dependencia lineal entre los inventarios de y los promedios históricos de las precipitaciones, con un coeficiente de correlación de 0.94. Esta función lineal se podrá utilizar en la estimación de los inventarios de referencia donde sea complejo encontrar sitios de referencia y por el contrario se disponga de suficiente información respecto a las precipitaciones.

For the successful application of the technique in soil erosion studies, it is necessary to establish the reference inventory correctly as it represents the total entrance of this radionuclide into the earth’s surface. In this sense, a site that has not been perturbed neither for the erosion nor for the deposit, is selected as reference site. In practice to find such sites is usually difficult. The objective of this research was to establish the reference inventory of for the studied localities of Cienfuegos province. It was established that the confidence interval at 90% of probability of the reference inventory is [1082; 1266] , and the variation coefficient of the reference inventory in the researched localities was of 11%. These values are in correspondence with those reported by other authors for similar places. Also the lineal dependence between the inventories of and the historical averages of the precipitations was determined, with a correlation coefficient of 0.94. This lineal function will be able to be used to obtain or to confirm the reference inventories from rainfall data.

Validade comercial de filés de Tilápia do Nilo (Oreochromis niloticus) resfriados embalados em atmosfera modificada e irradiados / Shelf life of refrigerated tilapia fillets (Oreochromis niloticus) packed in modified atmosphere and irradiated

O objetivo do presente estudo foi avaliar os efeitos dos processos de irradiação (com dose de 1,5kGy) e embalagem em atmosfera modificada (60% N2 e 40% CO2), aplicados isoladamente ou combinados, na extensão da validade comercial de filés de Tilápia do Nilo (Oreochromis niloticus) resfriados. Nos experimentos, foram utilizados 120 filés separados em lotes, de acordo com o tratamento: (T1) embalagem em ar (controle), (T2) embalagem em atmosfera modificada, (T3) embalagem em ar e irradiação, (T4) embalagem em atmosfera modificada e irradiação. Foram realizadas análises físico-químicas (BVT, TMA, pH, amônia e TBARS), bacteriológicas (contagem de bactérias heterotróficas, aeróbias, mesófilas e psicrotróficas) e avaliação sensorial. Os resultados consistentemente indicaram uma redução progressiva da qualidade do produto com o tempo de armazenamento, a qual foi significativamente mais rápida nas amostras controle do que naquelas submetidas aos demais tratamentos, tendo sido observada uma extensão na validade comercial dos filés embalados em atmosfera modificada e/ou irradiados de 4 dias para aproximadamente duas semanas.

This paper investigated the effects of modified atmosphere packing (60% N2 and 40% CO2) and irradiation (with a 1.5kGy dose) either used alone or combined on the shelf life of fillets of refrigerated Nile Tilapia. A total of 120 fillets were used in the experiments in order to test four different treatments and included samples: packed in air (control), packed in modified atmosphere, packed in air and irradiated, and finally, packed in modified atmosphere and irradiated. Regular monitoring of physicochemical parameters (TVB, pH, ammonia and TBARS), bacteriological conditions (heterotrophic aerobic mesophilic and psychrotrophic bacteria) and sensory acceptance were performed. The results consistently indicated an increasing deterioration of the fillets with time, however those treated with irradiation, modified atmosphere or both combined had longer shelf lives (around two weeks) in comparison with the control (4 days only).

Estudio de la erosión de los suelos en áreas protegidas de Cienfuegos, utilizando el cesio 137 como radiotrazador / Soil erosion studies in protected areas of Cienfuegos, using cesium 137 as radiotracer

RESUMEN Las explosiones nucleares de gran potencia a cielo abierto, debido a las pruebas de armas nucleares o como consecuencia de accidentes que han tenido lugar, son las principales causas de que gran número de radionúclidos se haya dispersado en todo el globo terráqueo. Entre estos se encuentra el cesio-137, que al llegar al suelo se adhiere fuertemente a sus partículas más finas. Ello, junto a su período de semidesintegración de 30 años y su fácil detección por gamma espectrometría hacen que se use como radiotrazador de los movimientos del suelo. Esta técnica, ampliamente usada y validada en diferentes entornos en todo el mundo, también fue previamente validada y se demostró su eficacia en la provincia de Cienfuegos. El objetivo de esta investigación fue estudiar mediante el uso del cesio 137, la redistribución del suelo y cuantificar la erosión en áreas protegidas de la provincia, donde las pérdidas de suelo y el arrastre de sedimentos son las principales causas del deterioro de estos ecosistemas con las consiguientes pérdidas económicas y ambientales. Los resultados obtenidos se interpolaron, empleando el método kriging mediante el software gvSIG, obteniendo un mapa de la distribución del suelo en las parcelas estudiadas, y garantizando una mejor visibilidad al respecto. El método se puede aplicar en otros lugares donde sea necesario conocer la magnitud de los problemas de erosión y la redistribución del suelo en el paisaje, lo cual puede ser muy útil para trazar los planes de reordenamiento de los usos del suelo.

ABSTRACT The large-scale nuclear explosions as a result of nuclear weapons tests or nuclear accidents are the main causes of/for the great dispersion of artificial radionuclides all over the world. One of these radionuclides is cesium-137, which is strongly fixed to the fine soils particles. This fact, together with its half-life of 30 years and its easy detection by gamma spectrometry have turned cesium 137, in a good radiotracer of soil movement. This technique has been widely used and validated in different landscapes throughout the world. Its effectiveness was also previously validated and proved in Cienfuegos province as well. This research was aimed at using the cesium-137 technique to study soil redistribution and quantify erosion in the so called Protected Areas in Cienfuegos province, where soil loss and sediment transport are the main causes of deterioration of these ecosystems with the consequent economic and / or environmental losses. The results were represented in a map using the gvSIG software by kriging, thus achieving greater visibility of the soil redistribution in the studied plot. The methodology used in this study could be used in other places wherever the magnitude of erosion problemsas well as knowing the soil redistribution plot pattern in the landscape are necessary and very useful to elaborate plans for rearrangement in land use management.

Assesment of soil erosion by 137Cs technique in native forests in Londrina City, Parana, Brazil

The aim of this work was to assess the soil erosion process in native forest by the 137Cs methodology. The mass balance model was applied to assess the rates of soil loss in three native forests around of Londrina city, Paraná, Brazil. 137Cs distribution depth was of exponential type for the three forests and 137Cs inventory was 241 Bq m-2 for Mata 1, 338 Bq m-2 for Mata 2 and 325 Bq m-2 for Mata UEL. The soil loss value calculated for three native forests was: 6,684 kg ha-1 yr-1 for Mata 1, 1,788 kg ha-1 yr-1 for Mata 2 and 4,524 kg ha-1 yr-1 for Mata UEL.

O processo de erosão de solo em floresta nativa tem sido pouco investigado. Como a metodologia do césio-137 dá resultados tanto de taxas de erosão de solo como a bioturbação no perfil de solo, ele tem sido usado para avaliar o processo de erosão de solo nestes ecossistemas. O modelo de balanço de massa foi aplicado para avaliar as taxas de perdas de solo em três florestas nativas na região de Londrina, Paraná, Brasil. A distribuição em profundidade do césio-137 para as três florestas é do tipo exponencial. O inventário de césio-137 foi de 241 Bq m-2 para Mata 1, 338 Bq m-2 para Mata 2 e 325 Bq m-2 para Mata UEL.O valor de perda de solo calculado para Mata 1 foi 6,684 kg ha-1 yr-1, 1,788 kg ha-1 yr-1 para Mata 2 e 4,524 kg ha-1 yr-1 para Mata UEL.

Desarrollo de un nuevo tipo de generador radisotópico de / / Development of a new type of / radioisotope generatorc

Se brindan los resultados del desarrollo y el comportamiento de un nuevo tipo de generador piloto de /. Empleando CsCl estable y radiactivo se realizaron ensayos en batch y en columna con el objetivo de determinar los parámetros de sorción para tres tipos diferentes de resina de intercambio iónico de hexacianoferrato de cobre y potasio inmovilizada en silicagel. Los resultados mostraron que la capacidad de sorción de estos sistemas puede alcanzar valores en el orden de 112 mmol/Kg de resina seca comparable con los reportados en la literatura. La retención de más del 95% de cesio y la sorción prácticamente nula del bario mostraron la alta eficiencia de estos sistemas para la separación de estos dos elementos. A partir de estos resultados se desarrolló y construyó un pequeño generador piloto de /, empleando la misma estructura física de un generador decaído de con una actividad nominal de 18,5 KBq y con una eficiencia de elución cercana al 99% que confirma la hipótesis inicial sobre la separación efectiva del par / en estos sistemas. La realización de más de 20 eluciones después de casi año y medio de trabajo con relevantes características hidrodinámicas y la ausencia de en las soluciones eluidas demostraron la relativa larga funcionalidad de este nuevo tipo de generador radisotópico de /.

Results of the development and performance of a new type of /. generator are presented. Batch and column tests employing stable and radioactive CsCl were performed in order to determine the sorption parameters for three different cupper potassium hexacianferrate immobilized on silicagel ion exchange resin. Results showed that the sorption capacity of these systems can reach values in the order of 112 mmol/Kg of dry resin, comparable with those reported in the literature. The retention of more than 95% of cesium with practically no sorption of Barium, showed the high efficiency of these systems for the separation of these two elements. From these results a pilot small / generator, employing the same physical structure of a decayed generator, has been developed and constructed with a nominal activity of 18.5 KBq and a elution efficiency close to 99% that confirms the initial hypothesis of the separation of the pair / in these systems. More than 20 elutions performed after nearly a year and a half working with reliable hydrodynamic characteristics and the absence of in the eluted solution demonstrate the relative long functionality of the new type of / generator, that undoubtedly erect as the scientific newness of the present work.