M. A. Gryziński

Characterisation of radiation field for irradiation of biological samples at nuclear reactor—comparison of twin detector and recombination methods

Central Laboratory for Radiological Protection is involved in achieving scientific project on biological dosimetry. The project includes irradiation of blood samples in radiation fields of nuclear reactor. A simple facility for irradiation of biological samples has been prepared at horizontal channel of the nuclear reactor MARIA in NCBJ in Poland. The radiation field, composed mainly of gamma radiation and thermal neutrons, has been characterised in terms of tissue kerma using twin-detector technique and recombination chambers.

Experimental investigation on radiation shielding of high performance concrete for nuclear and radiotherapy facilities

Abstract This paper presents the set of procedures developed in Radiation Protection Measurements Laboratory at National Centre for Nuclear Research for evaluation of shielding properties of high performance concrete. The purpose of such procedure is to characterize the material behaviour against gamma and neutron radiation. The range of the densities of the concrete specimens was from 2300 to 3900 kg/m3. The shielding properties against photons were evaluated using 137Cs and 60Co sources. The neutron radiation measurements have been performed by measuring the transmitted radiation from 239PuBe source. Scattered neutron radiation has been evaluated using the shadow cone technique. A set up of ionization chambers was used during all experiments. The gamma dose was measured using C-CO2 ionization chamber. The neutron dose was evaluated with recombination chamber of REM-2 type with appropriate recombination method applied. The method to distinguish gamma and neutron absorbed dose components in mixed radiation fields using twin detector method was presented. Also, recombination microdosimetric method was applied for the obtained results. Procedures to establish consecutive half value layers and tenth value layers (HVL and TVL) for gamma and neutron radiation were presented. Measured HVL and TVL values were linked with concrete density to highlight well known dependence. Also, influence of specific admixtures to concrete on neutron attenuation properties was studied. The results confirmed the feasibility of approach for the radiation shielding investigations.

Ambient dose equivalent measurements in secondary radiation fields at proton therapy facility CCB IFJ PAN in Krakow using recombination chambers

Abstract This work presents recombination methods used for secondary radiation measurements at the Facility for Proton Radiotherapy of Eye Cancer at the Institute for Nuclear Physics, IFJ, in Krakow (Poland). The measurements of H*(10) were performed, with REM-2 tissue equivalent chamber in two halls of cyclotrons AIC-144 and Proteus C-235 and in the corridors close to treatment rooms. The measurements were completed by determination of gamma radiation component, using a hydrogen-free recombination chamber. The results were compared with the measurements using rem meter types FHT 762 (WENDI-II) and NM2 FHT 192 gamma probe and with stationary dosimetric system.

A ring-shaped recombination chamber for hadron therapy dosimetry

An innovative recombination chamber has been designed for estimation of stray radiation doses and quality factors in hadron therapy. The chamber allows for determination of absorbed dose and recombination index of radiation quality in phantoms at small distances from simulated organs. The chamber body and electrodes are ring shaped, so the beam may be directed through the empty centre of the ring. The ionisation of the filling gas is caused by secondary or scattered radiation and can be related to the dose absorbed in the tissues close to the irradiated target volume.

INVESTIGATION ON RADIATION SHIELDING PROPERTIES OF SPECIAL CONCRETE IN NEUTRON FIELDS

This paper presents the results on radiation shielding of special types of concrete, designed for nuclear reactor containments. The research focused on the study of shielding properties against neutron component of ionizing radiation. For this purpose, two types of ionizing source were used: the isotopic reference neutron field of 239Pu-Be in calibration laboratory and the MARIA Research Reactor.

Study on the influence of the B4C layer thickness on the neutron flux and energy distribution shape in multi-electrode ionisation chamber.

A model of a multi-electrode ionisation chamber, with polypropylene electrodes coated with a thin layer of B4C was created within Monte Carlo N-Particle Transport Code (MCNPX) and Fluktuierende Kaskade (FLUKA) codes. The influence of the layer thickness on neutron absorption in B4C and on the neutron spectra in the consecutive intra-electrode gas volumes has been studied using the MCNPX and FLUKA codes. The results will be used for designing the new type of the ionisation chamber.

A micro-gap, air-filled ionisation chamber as a detector for criticality accident dosimetry

A micro-gap air-filled ionisation chamber was designed for criticality dosimetry. The special feature of the chamber is its very small gap between electrodes of only 0.3 mm. This prevents ion recombination at high dose rates and minimises the influence of gas on secondary particles spectrum. The electrodes are made of polypropylene because of higher content of hydrogen in this material, when compared with soft tissue. The difference between neutron and gamma sensitivity in such chamber becomes practically negligible. The chambers envelope contains two specially connected capacitors, one for polarising the electrodes and the other for collecting the ionisation charge.

A Method of determination of ambient quality factor of fast neutrons in mixed radiation fields using advanced recombination methods

Sposób wyznaczania przestrzennego współczynnika jakości neutronów prędkich w polach promienowania mieszanego wykorzystujacy zaawansowane metody rekombinacyjne Przedstawiono sposób wyznaczania przestrzennego współczynnika jakości neutronów prędkich, Qn*(10), w polu promieniowania mieszanego o nieznanym, lecz ograniczonym, widmie energii neutronów. W tym sposobie wykorzystuje się korelacje między wartościami Qn*(10), obliczonymi metodą Monte Carlo dla neutronów monoenergetycznych, a parametrami doświadczalnych charakterystyk nasycenia komory rekombinacyjnej, umieszczonej we wzorcowych polach neutronów monoenergetycznych wraz z towarzyszącym promieniowaniem gamma. Omija się przy tym szereg niepewności, m.in. związanych z brakiem pełnej odpowiedniości między współczynnikiem jakości promieniowania a parametrami, od których zależy lokalna rekombinacja jonów, a także z brakiem pełnej odpowiedniości konstrukcji komory rekombinacyjnej z tzw. kulą MKJR (ang. ICRU) definiującą wielkości operacyjne H*(10) i Q*(10). A Method of determination of ambient quality factor of fast neutrons in mixed radiation fields using advanced recombination methods The paper presents a method for determination of ambient quality factor for fast neutrons, Qn*(10), in mixed radiation fields with unknown neutron energy spectrum of limited energy range. The method uses a correlation between the Qn*(10) values, calculated by Monte-Carlo method for monoenergetic neutrons, with parameters of saturation curves of the recombination chamber, determined experimentally in the fields of monoenergetic neutrons and accompanying gamma radiation. In such a way, a number of discrepancies can be omitted, among them those associated with limited conformity between radiation quality factor and parameters of initial recombination of ions, as well as between construction of the recombination chamber and ICRU sphere, for which the quantities H*(10) and Q*(10) were defined.

Application of recombination chambers for determination of neutron ambient dose equivalent at the door to the maze of linear accelerator vault

Application of recombination chambers for determination of neutron ambient dose equivalent at the door to the maze of linear accelerator vault Recombination chambers and 2202D Studsvik-Alnor reference remmeter were used for determination of ambient dose equivalent, H*(10) and its neutron and gamma components at the door to the maze of 15 MV medical accelerator. The measurements were performed at opened and partly closed door. The results showed that the ambient dose equivalent rate was 76.2 μSv h-1 at the opened door and only 2.7 μSv h-1 at slightly opened door, 2.5 m from the entrance to the maze.

Ionisation Chambers Containing Boron as Neutron Detectors in Mixed Radiation Fields

Ionisation Chambers Containing Boron as Neutron Detectors in Mixed Radiation Fields The paper presents a newly designed ionisation chambers containing boron, operated in the initial recombination regime. The chambers were either filled with BF3 or the chamber electrodes were covered with B4C. The chambers can be placed in paraffin moderators. The sensitivity of the chambers was investigated depending on gas pressure, moderator thickness and polarizing voltage. The results showed that it was possible to obtain nearly the same sensitivity of the chamber to H* (10) for photons and neutrons in restricted energy range, however further investigations are needed to make an optimum design. The examples of applications for dosimetric measurements in mixed radiation fields near medical linear accelerator and in the vicinity of high-energy proton accelerator are presented.