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Demetrio Gregoratto

Demetrio Gregoratto
UK Health Security Agency

PhD
Radiation protection scientist

About

44
Publications
4,990
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999
Citations
Citations since 2017
12 Research Items
356 Citations
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2017201820192020202120222023020406080
2017201820192020202120222023020406080
2017201820192020202120222023020406080

Publications

Publications (44)
Article
Full-text available
The aim of CONFIDENCE WP2 is to improve the situation awareness in the early phase of a nuclear accident by trying to reduce the uncertainty in individual dose assessment when dealing with external and internal exposures. Main WP2 research actions to improve external dosimetry in this emergency frame were the development of destruction-free protoco...
Article
The paper presents a “one-step” procedure for the direct dose assessment based on thyroid monitoring data obtained after a severe nuclear accident at a light water power reactor. The developed methodology is based on the “dose per content” concept that allows the direct conversion of the measured value to the dose estimate. The paper provides metho...
Article
Following a nuclear incident, ¹³¹ I monitoring is usually carried out by performing in vivo measurements of the retained activity in the thyroid. The measurement equipment needs to be calibrated in order to convert thyroid count rates into retained activity. This calibration relies on measurements or Monte Carlo computations using appropriate anthr...
Article
Full-text available
Following a severe nuclear reactor accident large amounts of radioactive iodine are released in the atmosphere. Health consequences estimation for the affected population is based on the dose assessment which can be derived from in vivo measurements. Since the uptake of radioactive iodine increases the thyroid cancer risk of children it is of parti...
Article
Following inhalation of an aerosol of relatively insoluble particles, it is usually found that the fractional dissolution rate of material retained in the lungs decreases with time, and the amount remaining undissolved can be represented simply by a decreasing exponential function with two or more components. A few exceptions are known, in which th...
Book
Abstract –: The 2007 Recommendations of the International Commission on Radiological Protection (ICRP, 2007) introduced changes that affect the calculation of effective dose, and implied a revision of the dose coefficients for internal exposure, published previously in the Publication 30 series (ICRP, 1979, 1980, 1981, 1988) and Publication 68 (IC...
Book
The 2007 Recommendations of the International Commission on Radiological Protection (ICRP, 2007) introduced changes that affect the calculation of effective dose, and implied a revision of the dose coefficients for internal exposure, published previously in the Publication 30 series (ICRP, 1979, 1980, 1981, 1988) and Publication 68 (ICRP, 1994). In...
Technical Report
Full-text available
This report summarizes the findings about parameters influencing thyroid in vivo monitoring of 131 I. The parameters were studied by Monte Carlo calculations using realistic anthropomorphic voxel phantoms and four previously validated detector models (3 NaI detectors and 1 Germanium detectors). The voxel phantoms corresponded to the following ages:...
Technical Report
Full-text available
DESCRIPTION This report gives technical guidelines for radio-iodine monitoring following a nuclear incident. Monitoring aspects addressed include the choice of detectors, the calibration and measurement process, factors affecting measurements, measurement uncertainties, the preparation of equipment and measurement locations, the measurement time, t...
Technical Report
Full-text available
DESCRIPTION This report presents the result of the work carried out by the Work Package 6 of the CAThyMARA project. This work focused on the direct assessment of the thyroid dose or committed effective dose from measurements. As a result dose per content functions are derived for different ages (new born, 1,5,10,15-years old children and adult) and...
Article
In the Mayak Worker Dosimetry System (MWDS-2013), intakes of plutonium and organ doses are assessed on the basis of measurements made on the plutonium content of 56 400 urine samples. Altogether, there were urine bioassays for 7591 (29%) of the 25 757 cohort members who were employed any time at Mayak between 1948 and 1982. These measurements are s...
Article
In 1983, a young man inhaled accidentally a large amount of plutonium and americium. This case was carefully followed until 2013. Since no decorporation measures had been taken, the undisturbed metabolism of Pu and Am can be derived from the data. First objective was to determine the amount of inhaled radionuclides and to estimate committed effecti...
Article
Purpose: This paper reviews data related to the behavior of the lanthanoid elements (lanthanum through lutetium, atomic numbers 57-71) in the human body and proposes biokinetic models for internally deposited radio-lanthanoids in workers. Materials and methods: Published data on the following topics are reviewed and analyzed: Physico-chemical pr...
Article
The European Commission project IDEAS has produced guidelines for internal dose assessments from monitoring data. A key stage in the guidelines requires assessment of the goodness-of-fit of biokinetic models to bioassay data. The present note extends the use of an autocorrelation coefficient to assess the fits of multiple types of bioassay quantity...
Article
To facilitate the estimation of radiation doses from intake of radionuclides, the International Commission on Radiological Protection (ICRP) publishes dose coefficients (dose per unit intake) based on reference biokinetic and dosimetric models. The ICRP generally has not provided biokinetic models or dose coefficients for intake of noble gases, but...
Article
Epidemiological studies on uranium miners are being carried out to quantify the risk of cancer based on organ dose calculations. Mathematical models have been applied to calculate the annual absorbed doses to regions of the lung, red bone marrow, liver, kidney and stomach for each individual miner arising from exposure to radon gas, radon progeny a...
Article
New information on particle retention of inhaled insoluble material indicates that the ICRP Human Respiratory Tract Model (HRTM) significantly underestimates long-term retention in the lungs. In a previous paper, the information from three studies was reviewed, and a model developed to predict particle retention in the lungs of coal miners was adap...
Article
Lung cancer is a well-known effect of radon exposure in uranium mines. However, little is known about the induction of leukemia by radiation exposure in mines. Moreover, miners usually have occupational medical checkup programs that include chest x-ray examinations. Therefore, the aim of the present study was to re-examine leukemia risk among miner...
Article
Better information is available now on long-term particle retention in the human lungs than there was in 1994, when the human respiratory tract model (HRTM) was adopted by the International Commission on Radiological Protection (ICRP). Three recent studies are especially useful because they provide such information for groups of people who inhaled...
Article
Full-text available
A two-dimensional array of saddle coils at Mc poloidal and Nc toroidal positions is used on the EXTRAP T2R reversed-field pinch (Brunsell P R et al 2001 Plasma Phys. Control. Fusion 43 1457) to study active control of resistive wall modes (RWMs). Spontaneous growth of several RWMs with poloidal mode number m = 1 and different toroidal mode number n...
Article
A system of evenly spaced poloidal arrays of saddle coils was recently installed on the reversed field pinch device EXTRAP T2R to perform experiments on the active control of MHD modes. The implementation of different control strategies, such as “intelligent shell” and “mode control”, was made possible by a flexible digital control system. After gi...
Article
Arrays of magnetic coils and sensors in the EXTRAP T2R [ P. R. Brunsell et al., Plasma Phys. Controlled Fusion 43 1457 (2001) ] reversed-field pinch have been used to investigate the plasma response to an applied resonant magnetic perturbation in the range of the resistive-wall modes (RWMs). Measured RWM growth rates agree with predictions of a cyl...
Article
An array of saddle coils having Nc = 16 equally spaced positions along the toroidal direction has been installed for feedback control of resistive wall modes (RWMs) on the EXTRAP T2R reversed-field pinch [ P. R. Brunsell, H. Bergsaker, M. Cecconello et al., Plasma Phys. Controlled Fusion 43, 1457 (2001) ]. Using feedback, multiple nonresonant RWMs...
Article
Full-text available
Active feedback control of resistive wall modes (RWMs) has been demonstrated in the EXTRAP T2R reversed-field pinch experiment. The control system includes a sensor consisting of an array of magnetic coils (measuring mode harmonics) and an actuator consisting of a saddle coil array (producing control harmonics). Closed-loop (feedback) experiments u...
Article
Full-text available
Active feedback stabilization of multiple independent resistive wall modes is experimentally demonstrated in a reversed-field pinch plasma. A reproducible simultaneous suppression of several nonresonant resistive wall modes is achieved. Coupling of different modes due to the limited number of the feedback coils is observed in agreement with theory....
Article
We report here on MHD active control experiments performed in the Extrap T2R device, which has been recently equipped with a set of 32 feedback controlled saddle coils couples. Experiments aiming at selectively exciting a resonant resistive instability in order to actively induce Quasi Single Helicity states will be presented. Open loop experiments...
Article
Full-text available
EXTRAP T2R mode control system The EXTRAP T2R device is a thin shell medium size RFP (R/a=1.24/0.183 m) (2). The thin wall stainless steel corrugated vacuum chamber of the device is placed inside a closely fitting thin shell at a radius r/a=1.08, having a vertical field penetration time of v=6.3 ms. In the present experiments, the plasma current i...
Article
For the success of thermonuclear fusion by magnetic confinement it is important to improve on the stability limits imposed by large-scale magnetohydrodynamics (MHD) instabilities. This thesis focuses on the stabilisation of the "resistive-wall mode" (RWM), an instability which affects high-pressure tokamaks but also Reversed Field Pinches (RFP). In...
Article
Feedback control of nonaxisymmetric resistive wall modes is studied analytically for cylindrical plasmas and computationally for high beta tokamaks. Internal poloidal sensors give superior performance to radial sensors, for instance in terms of the highest achievable plasma pressure. A single poloidal array of feedback coils allows robust control w...
Article
Feedback stabilization of magnetohydrodynamic modes in reversed field pinches is analysed for a set of discrete coils driven by voltage control. It is found that the resistive wall mode can be stabilized with a very simple controller structure and with acceptable voltages in the coils. These results are obtained by using a sufficient number of acti...
Article
The theory of resistive wall modes (RWMs) is discussed and compared with experimental results. Special attention is given to the possibilities of stabilizing the RWM by plasma rotation and active feedback. A simple cylindrical model is used to illustrate various aspects of active control. Fully toroidal computations are also presented, including pr...
Conference Paper
A multivariable electromagnetic model for the active control of resistive wall modes in RFP devices was developed. It accounts for the dynamic behaviour of both the saddle coil currents and the plasma modes. Side-bands effects due to the finite numbers of active coils and sensors are properly considered. First simulations of closed loop stabilizati...
Article
Scientific and technical activities on JET focus on the issues likely to affect the ITER design and operation. Our understanding of the ITER reference mode of operation, the ELMy H-mode, has progressed significantly. The extrapolation of ELM size to ITER has been re-evaluated. Neoclassical tearing modes have been shown to be meta-stable in JET, and...
Article
Feedback stabilization of magnetohydrodynamical modes in reversed field pinches is studied in cylindrical geometry, taking into account a finite number of coils, both in poloidal and toroidal directions. The robustness and stability of the feedback scheme is analysed by means of Nyquist diagrams for different arrangements of the feedback coils and...
Article
The large-aspect-ratio model for current-driven external kinks is applied to study control of non-axisymmetric resistive wall modes in tokamaks. Comparison with toroidal computations indicates that the cylindrical instabilities react in similar ways to feedback as the pressure-driven toroidal modes, when the feedback and sensor coils are placed on...
Article
Density profiles measured in RFX by a 13 chord mid-infrared (MIR) interferometer are found to be flat or hollow. Density gradients are large only in a region typically of the order of 2 to 4 cm from the edge. A detailed investigation of the form of the electron density profile during the current flat-top phase in different experimental conditions h...
Article
Full-text available
The article presents an overview of recent experimental results obtained on the RFX device. The authors obtained and studied a reversed field pinch plasma with a plasma current of up to 1 MA, negligible radiation losses and low effective charge. The local power and particle balance shows that in standard operation the plasma core is dominated by ma...
Article
Active feedback stabilization of resistive wall modes in tokamaks is studied both analytically, using large aspect ratio theory, and by means of toroidal computations. Extensive studies show that robust stabilization, with respect to variations in plasma current, pressure and flow velocity, can be achieved with a simple control system using poloida...
Article
The influence of non-uniform toroidal plasma rotation on the stability of resistive wall modes is analysed for high-β advanced tokamak equilibria, using toroidal ideal MHD. For advanced tokamak equilibria with qmin in the range of 1.6-2.1, a main role is played by the rotation at the resonance where q2. A rotation frequency of at least 3% of the ce...
Article
To the present knowledge, the most fundamental issue for RFP confinement devices is, in a proper sense [1,2,3], the existence itself of such MHD quasi-equilibria, The purpose of this paper is carry out a kinetic analysis of the conditions of their existence. In addition, the role of toroidal and poloidal rotation, strong equilibrium drift, as well...
Article
A new non-perturbative and non-variational solution method is proposed for the gyrokinetic equation, based on a suitable approximation for the linearized Fokker-Planck collision operator. The approach, which allows, in principle, the accurate evaluation of arbitrary moments of the distribution function for a weakly collisional magnetoplasma with to...

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