Study of Fast Transient Pressure Drop in VVER-1000 Nuclear Reactor Using Acoustic Phenomenon

This article aims to simulate the sudden and fast pressure drop of VVER-1000 reactor core coolant, regarding acoustic phenomenon. It is used to acquire a more accurate method in order to simulate the various accidents of reactor core. Neutronic equations should be solved concurrently by means of DRAGON 4 and DONJON 4 coupling codes. The results of the developed package are compared with WIMS/CITATION and final safety analysis report of Bushehr VVER-1000 reactor (FSAR). Afterwards, time dependent thermal-hydraulic equations are answered by employing Single Heated Channel by Sectionalized Compressible Fluid method. Then, the obtained results were validated by the same transient simulation in a pressurized water reactor core. Then, thermal-hydraulic and neutronic modules are coupled concurrently by use of producing group constants regarding the thermal feedback effect. Results were compared to the mentioned transient simulation in RELAP5 computer code, which show that mass flux drop is sensed at the end of channel in several milliseconds which causes heat flux drop too. The thermal feedback resulted in production of some perturbations in the changes of these parameters. The achieved results for this very fast pressure drop represent accurate calculations of thermoneutronic parameters fast changes

Neutronic simulation of a CANDU-6 reactor with heavy water-based nanofluid coolant

In recent years, extended studies are developed for investigation the effects of using nanofluids in NPP as coolant. CANDU-6 reactors have the potential to use nanofluid coolants because in these reactors, the moderator system is fully independent of the primary heat transport system. MCNPX code has been used for modelling and simulation of a CANDU-6 reactor containing a nanofluid as primary coolant. The variation of multiplication factor and total neutron flux distribution along a fuel channel, next to the central axis, has been investigated by using different nanofluids. In this analysis, heavy water-based nanofluids containing various volumetric percentages of Al2O3, TiO2, CuO, Ti, Cu, Zr, and Si nanoparticles were used. A typical CANDU-6 reactor was selected as reference for reactor core modelling. The results of the neutronic analysis show that Al2O3 nanofluids with 1% volumetric percentage are the most suitable coolant for CANDU-6 reactors which can increase the coolant heat transfer coefficient and consequently enhance the plant efficiency

Presenting and simulating an innovative model of liver phantom and applying two methods for dosimetry of it in neutron radiation therapy

AimA new model of liver phantom is defined, then this model is simulated by MCNPX code for dosimetry in neutron radiation therapy. Additionally, an analytical method is applied based on neutrons collisions and mathematical equations to estimate absorbed doses. Finally, the results obtained from two methods are compared to each other to justify the approach.BackgroundThe course of treatment by neutron radiation can be implemented to treat cancerous tissues, although this method has not yet been widespread.The MIRD and the Stylized Family Phantom were the first anthropomorphic phantoms, although the representation of internal organs was quite crude in them. At present, a water phantom is usually used for clinical dosimetry.Materials and methodsEach of the materials in an adult liver tissue including water and some organic compounds is decomposed into its constituent elements based on mass percentage and density of every element. Then, the accurate mass of every decomposed material of human liver tissue is correlated to masses of the phantom components.ResultsThe absorbed doses are computed by MCNPX simulation and analytical method in all components and different layers of this phantom.ConclusionsWithin neutron energy range of 0.001[[ce:hsp sp="0.25"/]]eV–15[[ce:hsp sp="0.25"/]]MeV, the calculated doses by MCNPX code are approximately similar to results obtained by analytical method, and the derived graphs of both methods approve one another. It is also concluded that through increasing the incident neutron energy, water receives the largest amounts of absorbed doses, and carbon, nitrogen and sulfur receive correspondingly less amounts, respectively