OVERVIEW OF NEUTRON MEASUREMENTS IN JET FUSION DEVICE.

The design and operation of ITER experimental fusion reactor requires the development of neutron measurement techniques and numerical tools to derive the fusion power and the radiation field in the device and in the surrounding areas. Nuclear analyses provide essential input to the conceptual design, optimisation, engineering and safety case in ITER and power plant studies. The required radiation transport calculations are extremely challenging because of the large physical extent of the reactor plant, the complexity of the geometry, and the combination of deep penetration and streaming paths.

Occupational radiation exposure during removal of radioactive reactor components from GRR-1 pool.

The aim of the study was to control occupational exposure during the removal of radioactive reactor components from a Greek research reactor pool. The method comprised the prediction of the radiation levels, the design of special shielding structures and the occupational dose assessment. Activation calculations were performed using the FISPACT code to predict the source term.

Application of the Monte Carlo method for the calibration of an in situ gamma spectrometer.

A MCNP model was developed for the efficiency calibration of an in situ gamma ray spectrometry system based on a high purity germanium (HPGe) detector. The detector active crystal volume was adjusted semi-empirically against experimental measurements. Calculated full energy peak efficiency curves, over the photon energy range between 50 keV and 5 MeV, are presented for surface and slab source configurations.

An MCNP-based model for the evaluation of the photoneutron dose in high energy medical electron accelerators.

The development of a computational model for the treatment head of a medical electron accelerator (Elekta/Philips SL-18) by the Monte Carlo code mcnp-4C2 is discussed. The model includes the major components of the accelerator head and a pmma phantom representing the patient body. Calculations were performed for a 14 MeV electron beam impinging on the accelerator target and a 10 cmx10 cm beam area at the isocentre.

Nondestructive characterization of radioactive waste drums by gamma spectrometry: a Monte Carlo technique for efficiency calibration.

A semi-empirical non-destructive technique to assay radioactive waste drums is presented. The technique is based on gamma spectrometry performed using a portable NaI detector and Monte Carlo simulations using the MCNP code in order to derive the gamma ray detector efficiency for the volume source. The derivation of detector efficiency was performed assuming homogeneous distribution of the source activity within the matrix material.

Large sample neutron activation analysis: a challenge in cultural heritage studies.

Large sample neutron activation analysis compliments and significantly extends the analytical tools available for cultural heritage and authentication studies providing unique applications of non-destructive, multi-element analysis of materials that are too precious to damage for sampling purposes, representative sampling of heterogeneous materials or even analysis of whole objects. In this work, correction factors for neutron self-shielding, gamma-ray attenuation and volume distribution of the activity in large volume samples composed of iron and ceramic material were derived. Moreover, the effect of inhomogeneity on the accuracy of the technique was examined.

Prompt-gamma neutron activation analysis facility for in vivo body composition studies in small animals.

The design, calibration, dosimetry and performance evaluation of a prompt-gamma neutron activation analysis facility for in vivo body composition studies in small animals (i.e. rats or rabbits) is discussed.

Sodium bromide by instrumental neutron activation analysis quantifies change in extracellular water space with wound closure in severely burned children.

Background: The ability to measure extracellular water (ECW) in critically ill patients can significantly enhance current methods of assessing fluid homeostasis, body composition, and response to nutritional therapy. We measured corrected bromide space to determine change in ECW with wound closure among acutely burned children.

Methods: Fifteen children with burns over 30% of their total body surface area had their ECW determined following hemodynamic stabilization and when wound closure was complete.

Normalized conceptus doses for abdominal radiographic examinations calculated using a Monte Carlo technique.

The aim of the present study was to develop a reliable method for estimating conceptus radiation doses resulting from abdominal radiographic examinations for all trimesters of pregnancy. The method is based on normalized conceptus doses estimated using Monte Carlo modeling. The Monte Carlo N-Particle (MCNP) radiation transport code was employed in the current study.

Personal neutron dosimetry at a research reactor facility.

Individual neutron monitoring presents several difficulties due to the differences in energy response of the dosemeters. In the present study, an individual dosemeter (TLD) calibration approach is attempted for the personnel of a research reactor facility. The neutron energy response function of the dosemeter was derived using the MCNP code.

Calibration of the Brookhaven National Laboratory delayed gamma neutron activation facility to measure total body calcium.

Differences in body size and shape can cause large variances in the in vivo results of neutron activation analysis. To introduce corrections for body size for the delayed gamma neutron activation facility at Brookhaven National Laboratory, "reference man"-sized and "reference woman"-sized phantoms were constructed. Simulation results using the Monte Carlo Neutron and Photon Transport code also provided correction factors for people of different sizes.

Evaluation of neutron dose in the maze of medical electron accelerators.

MCNP code was used to simulate neutron and prompt gamma ray transport for a range of maze geometrical parameters, wall composition, and wall surface lining. Verification measurements were performed at two medical electron accelerator facilities. A very good agreement was observed between the results of the measurements and the MCNP simulation.

In vivo body composition studies in rats: assessment of total body protein.

The precision and accuracy of a prompt-gamma neutron activation facility developed to assess total body protein in rats is estimated. The coefficient of variation of nitrogen measurement, as estimated by repeated measurements on 15 rats, was 5.5% for an equivalent dose of 60 mSv (Q = 20).

Improvement of the prompt-gamma neutron activation facility at Brookhaven National Laboratory.

The prompt-gamma neutron activation facility at Brookhaven National Laboratory was upgraded to improve both the precision and accuracy of its in vivo determinations of total body nitrogen. The upgrade, guided by Monte Carlo simulations, involved elongating and modifying the source collimator and its shielding, repositioning the system's two NaI(Tl) detectors, and improving the neutron and gamma shielding of these detectors. The new source collimator has a graphite reflector around the 238PuBe neutron source to enhance the low-energy region of the neutron spectrum incident on the patient.

A semiempirical method for the description of relative crossbeam dose profiles at depth from linear accelerators.

A semiempirical method for the calculation of the relative crossbeam dose profiles at depth is described. The parameters required to set up the formulae and their dependence with field size and depth are investigated. Using the above method, measured crossbeam dose profiles at depth from two linear accelerators, Philips (SL-18) and AEC (Therac-6) are reproduced.

Prompt-gamma neutron activation facility for measuring body nitrogen in vivo in small animals.

We have designed a prompt-gamma neutron activation facility for in vivo measurements of total body N in small animals. The facility incorporates a 252C neutron source with an emission rate of 3.2 x 10(8) n s-1 (140 micrograms), and a heavy-water neutron collimator-moderator assembly, together providing an optimum thermal flux-to-dose ratio for a 0.

Transurethral radiotherapy for benign prostatic hypertrophy-related urethral obstruction. Dosimetry, ethics, and preliminary results.

The aim of this study is to present our preliminary experience in treating BPH-related urine retention, resistant to other medical treatment, with transurethral brachytherapy. We also deal with dosimetric analysis so as to eliminate ethical concerns about the exposure of patients not suffering from cancer to a certain level of body irradiation. Patients suffering from BPH-related urethral obstruction were treated with two transurethral applications (three weeks apart) of Cs137 MDR, which delivered a total of 16 Gy, at 0.

Calibration for measuring total body nitrogen with a newly upgraded prompt gamma neutron activation facility.

A description is given of the calibration and performance of the upgraded facility at Brookhaven National Laboratory (BNL) for measuring total body nitrogen using the technique of prompt gamma neutron activation analysis. With the improved calibration, total body nitrogen can be more accurately measured not only in normal subjects but also in obese and wasted patients. Body hydrogen is used as an internal standard.

Design studies related to an in vivo neutron activation analysis facility for measuring total body nitrogen.

Design studies relating to an in vivo prompt capture neutron activation analysis facility measuring total body nitrogen are presented. The basis of the design is a beryllium-graphite neutron collimator and reflector configuration for (alpha, n) type radionuclide neutron sources (238PuBe or 241AmBe), so as to reflect leaking, or out-scattered, neutrons towards the subject. This improves the ratio of thermal neutron flux to dose and the spatial distribution of thermal flux achieved with these sources, whilst retaining their advantage of long half-lives as compared to 252Cf based systems.