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.

Influence of Polymer Modification on the Microstructure of Shielding Concrete

“…This was probably caused by adding too large an amount of fibers, leading to a drop in workability and to an increase in the dimensions of pores, which was proven using the image analysis method (Section 4.3). The literature confirms that low porosity is not the only condition which leads to good quality and durable concrete, since pore size distribution also plays an important role [15].…”

“…In the case of shielding against high-energy photons (gamma radiation) the increase in concrete density by change of aggregate type, e.g., from a normal to a heavy-weight type, is sufficiently effective [12,13]. Protection against neutrons is a more complex and sophisticated task [14][15][16], because neutrons are no-charge particles travelling in straight lines and interacting only with atomic nuclei while passing through matter. Neither the electrons surrounding a nucleus (the atomic electron cloud) nor the electric field caused by a positively charged nucleus affect a neutron's flight.…”

A Sub-Picoampere Measurement Algorithm for Use in Dosimetry of Time-Varying Radiation Fields

“…Such chambers are designed for environmental dosimetry measurements for radiation protection in radiation fields of unknown compositions and energy spectrums. They have been successfully used to study radiation fields produced by isotope sources, nuclear reactors [ 7 ] and research and medical accelerators [ 8 , 9 ]; radiation fields with high particle energies [ 10 , 11 , 12 ]; environmental measurements [ 1 ]; and neutron monoenergetic fields [ 6 ].…”

Badanie Osłonności Radiacyjnej Betonów Specjalnych

“…Badania osłonności próbek betonowych wykonane zostały w Hali Kalibracyjnej Narodowego Centrum Badań Jądrowych zgodnie z metodologią opracowaną na potrzeby badania osłonności różnego rodzaju materiałów osłonowych [2]. Jest to pomieszczenie badawczo-wzorcujące wyposażone m.in.…”

“…: liczymy warstwę połówkową HVL1 -osłabienie 0,5: szukamy punktu dla zlogarytmowanej wartości względnej prądów zmierzonych, która ma wartość najbliżej sprawdzanego osłabienia i wykorzystujemy parametry równania liniowego do obliczenia ilości płyt potrzebnych do otrzymania takiej osłonności); g) wyznaczamy grubości warstwy połówkowej; h) kolejną warstwę połówkową (HVL2), czyli ponowne osłabienie poziomu promieniowania, obliczamy przez odjęcie zgodnie z puntami f) i g) oraz dodatkowo odejmujemy wartość warstwy połówkowej poprzedniej; w ten sposób zawsze wyznaczamy grubość osłony, która obniży pole promieniowania o połowę. Znajomość kolejnych warstw półchłonnych pozwala określać współczynnik jednorodności promieniowania HF = HVL1/HVL2, którego znaczenie szerzej opisano w pracy [2].…”