Measurement of radioactivity in bottled drinking water in Spain.

The radioactive parameters in the Spanish regulations on water intended for human consumption (law decree 140/2003) have been determined in 30 different brands of some of the most common bottled mineral waters produced and consumed in Spain. These waters are not included in this legislation but if their consumption increases, the dose of radiation in the population may also increase. After gross alpha activity, gross beta activity, gross beta without potassium contribution and tritium activity had been determined, only a few samples (16% of the samples analysed) were over the normative limit for gross alpha activity (0.1 Bq/l), whereas all the samples were below the normative limits for the other parameters. For samples with high gross alpha activity values, (226)Ra and (224)Ra were determined. The values were between 0.01 and 1.52 Bq/l, and between 0.01 and 0.38 Bq/l, respectively, so alpha activity should be considered to be of natural origin.     

The separation of carrier-free 85Sr from a rubidium chloride cyclotron target

A method is presented for the separation of carrier-free ⁸⁵Sr from a rubidium chloride cyclotron target. The deuteron bombarded target is dissolved in 100 mL of 0.1 M hydrochloric acid. The solution is loaded onto an 8 mL column of AG50-X12 cation exchange resin and ⁸⁵Sr retained. The partially loaded rubidium is eluted with 250 mL of 0.5 M hydrochloric acid. Copper, iron and ⁶⁵Zn are eluted with 40 mL of 0.5 M hydrochloric acid-95% acetone. A final elution with 3.0 M nitric acid gives very high purity ⁸⁵Sr with a nearly 100% yield.     

Development of a simple neutron irradiation facility utilizing the stray neutron field of a medical cyclotron

During the routine isotope production schedule at the Australian National Medical Cyclotron thick copper plates, electroplated with enriched target materials, are bombarded with 30 MeV protons with an average beam current of 200 μA. As a result an intense high-energy, prompt neutron flux of the order of 1.72 × 10¹³ neutrons·cm⁻²·2⁻¹ is generated in the immediate vicinity of the target. The stray fast neutrons were moderated using a water-filled PVC bucket placed on the target station. A maximum thermal neutron flux of 3.88 × 10⁹ neutrons·cm⁻²·s⁻¹ was measured in the bucket using cobalt activation discs. The thermal neutrons from this irradiation facility has been used for the neutron activation analysis of trace elements in archaeological artefacts. It has also been planned to utilize the fast neutron flux by varying the geometry of the water moderator in order to estimate oxygen concentration in high-temperature superconductors and aluminium and silicon in ceramics.     

加速器治疗室内感生放射性研究现状

高能加速器缓发辐射危害不容忽视。本文对加速器治疗室内感生放射性产生的原理以及对患者、工作人员、公众等不同人群造成的危害作了综述性介绍；对加速器机头部结构材料处、治疗室空气中的感生放射性水平及有关影响因素的研究现状作了较详细的讨论；最后提出了目前研究中存在的问题及对今后研究的展望。     

加速器治疗室内感生放射性研究现状

高能加速器缓发辐射危害不容忽视。本文对加速器治疗室内感生放射性产生的原理以及对患者、工作人员、公众等不同人群造成的危害作了综述性介绍;对加速器机头部结构材料处、治疗室空气中的感生放射性水平及有关影响因素的研究现状作了较详细的讨论;最后提出了目前研究中存在的问题及对今后研究的展望。     

Measurement of low-level radioactivity in environmental samples by gamma-ray spectrometry

A low-level high-purity Ge detection system has been set up at about 15 m above the sea level in a normal counting room where the exposure rate is about 60 nSv h⁻¹. A background reduction is achieved by material selection, cryostat configuration and a single lead shielding. The integrated count rate within the energy interval 70 to 3000 keV is (0.498 ± 0.001) s⁻¹. The background in this energy range is reduced by a factor of about 100. An efficiency calibration of the detector in the energy range 50 to 2000 keV and according to the Marinelli-beaker configuration, type IEC-450, filled up with different matrices and suitable radionuclides has been performed.Field sampling of phragmites communis and juncus communis and gamma-ray measurements performed on dry matrices after treatment of the fresh material, indicate low-level contents of the nuclides ¹³⁴Cs, ¹³⁷Cs, ⁶⁰Co, ²³²Th, ²²⁶Ra, ⁷Be and ⁴⁰K distributed in the plants. It can be concluded that both selected plants are suitable bioindicators to measure the distribution of some anthropogenic and natural radionuclides in the environment.     

Measurement of natural radioactivity levels in Indian foodstuffs by gamma spectrometry

Measurements of natural radioisotopes present in some of the foodstuffs which form the main components of the composite Indian diet are presented. Assessment of daily intake of these natural radionuclides has been made on the basis of the average daily intake of these food-items by the population of Bombay and its environment. The content of ⁴⁰K, ²²⁶Ra and ²²⁸Th radioactivity varies from 45.9 to 649.0 Bq/kg, 0.01 to 1.16 Bq/kg and 0.02 to 1.26 Bq/kg, respectively. The average daily intakes of ⁴⁰K, ²²⁶Ra and ²²⁸Th have been estimated as 105.6, 0.17 and 0.18 Bq d⁻¹, respectively for the period 1970–1982.     

Comments on the feasibility of 61Cu production by proton irradiation of (nat)Zn on a medical cyclotron.

Feasibility of 61Cu production in high radionuclidic purity form via (nat)Zn(p,x) 61Cu nuclear process is discussed. Based on the experimentally available cross-sections of the (nat)Zn(p,x) 61Cu, (nat)Zn(p,x) 60Cu and (nat)Zn(p,x) 64Cu nuclear processes the usefulness of the (nat)Zn(p,x) 61Cu process for high-scale production is questionable in the 22 --> 12 MeV energy range.     

Measurement of the natural radioactivity at the international high energy stereoscopic system (HESS) project in Southern Africa.

The concentrations of the natural radionuclides 40K, 238U, and 232Th in soil samples taken from the international high energy stereoscopic system (HESS) project in Namibia have been determined using an HPGe detector and found to vary from 10.8 +/- 1.4 to 26.4 +/- 1.8 Bq kg(-1) for 238U, 12.8 +/- 2.4-52.3 +/- 3.7 Bq kg(-1) for 232Th and 212.1 +/- 12.1-683.8 +/- 27.1 Bq kg(-1) for 40K. The corresponding annual effective dose equivalent is 0.06 +/- 0.01 mSv y(-1) which is less than the limit of 1 mSv y(-1) recommended for the public by the ICRP.     

Photon beam attenuation for a patient support assembly during arc therapy for a medical linear accelerator.

Arc therapy is one of the treatment techniques for small, centrally located deep-seated tumors. However, care must be taken to remove any components that would interfere with the beam as the gantry rotates around the patient. One such component that may interfere with the beam is the patient support assembly (PSA) or treatment table. Beam attenuation factors due to the presence of the couch side-rails and the centerspine bar of the PSA are presented for both 6 MV and 18 MV photon beams of a Clinac 1800 during a 360 degrees rotation. Dose perturbations arising from these obstructions are displayed using an Alderson Rando phantom. A method is described to calculate the start and stop angles for the largest unobstructed arc for a given field size (FS), centerspine bar to the isocenter height (H), centerspine bar width (W), and SAD. As an illustration, for an SAD of 100 cm and a W of 4 cm, the start and stop angles for arc therapy with a FS of 10 x 10 cm2 and an H of 12.7 cm would be 29 degrees and 331 degrees.     

Separation of iron-55 from manganese cyclotron target material on a 2% cross-linked anion exchanger in hydrochloric acid

A simple method is presented for the separation of iron-55 from manganese cyclotron targets. Anion exchange chromatography with 9.0 M hydrochloric acid on a 2% cross-linked resin provides separation not only from large amounts of managanese but also from copper and zinc impurities. Separations are sharp and quantitative and less than 1 μg of manganese remains with the iron-55 when 2 g have been present originally.     

Measurement comparisons of radioactivity among European monitoring laboratories for the environment and food stuff

For more than 15 years, European Union (EU) laboratories monitoring environmental radioactivity have been obliged to participate in measurement comparisons organised by the European Commission. After a short review of comparisons conducted during the 1990s, the approach of IRMM organising these comparisons since 2003 is presented. It relies on the provision of comparison samples with reference values traceable to the International Reference System for radionuclides (SIR). The results of the most recent comparison, the determination of ⁴⁰K, ⁹⁰Sr and ¹³⁷Cs in milk powder, are presented. The influence of repetitive participation in measurement comparisons on laboratory performance is studied on the basis of data from more than 20 laboratories having participated in several exercises during the last 15 years.     

重混凝土屏蔽质子放疗机房的感生放射性估算

目的 估算肿瘤质子治疗时重混凝土屏蔽墙中铁元素因中子活化产生的感生放射性⁵⁶Mn及其水平。方法 采用Geant4程序构建某质子治疗机房的重混凝土屏蔽墙模型,模拟245 MeV的质子束照射水模体产生的次级中子,统计屏蔽墙内放射性核素⁵⁶Mn的分布。将屏蔽墙按每10 cm厚度分层,计算前3层屏蔽墙中放射性核素⁵⁶Mn产生的周围剂量当量率。结果 在最大的束流照射条件（1.872×10¹⁰个）下,前3层屏蔽墙内的放射性核素⁵⁶Mn个数分别为3.10×10⁸、1.60×10⁸和9.33×10⁸个;对治疗室内1 m远处产生的周围剂量当量率分别为2.13×10^-3、8.82×10^-4 和9.10×10^-4 μSv/h,总的周围剂量当量率为3.92×10^-3 μSv/h。结论 在质子治疗时,距离射束中心轴越近,屏蔽墙的感生放射性越强;屏蔽墙前端中子活化铁元素产生的感生放射性最强,感生放射性随着屏蔽墙厚度增大呈指数形式减小,应主要考虑质子治疗机房屏蔽墙前端产生的感生放射性。