Volume 85, Issue 3

Natural circulation loop (NCL) is mainly used as passive cooling system in nuclear power plants to ensure safety during pump failure and station blackout. Stable operation without flow instability is the most desirable operational mode of natural circulation loop for passive cooling. The present work deals with numerical analysis on the effect of inclination of horizontal leg of a rectangular loop working in single phase and presence of orifice on the thermohydraulic behaviour of NCL, using commercial CFD code ANSYS FLUENT 19.0. The effect of temporal variation of loop mass flow rate and temperature difference across the cooler section is compared for inclined loop with and without orifice. It is observed that the flow stability attained in the loop at inclination h = 308 can be achieved at h = 108 with orifice, with a reduction in the loop mass flow rate of 28.57%. The reduction in loop mass flow rate is accompanied by an increase in temperature difference across the cooler of 46.67%.

Segmented Gamma Scanner (SGS) is a commonly used nondestructive testing (Non-Destructive Assay NDA) method. SGS uses radial rotation, axial segmentation, segmented scanning of the non-uniform sample of the \homogenization", making it possible to accurately measure the radioactivity on each segment and is currently widely used in the field of arms control. This paper introduces a self-designed SGS measuring device and uses this device to perform a large number of subscanning experiments on different measurement objects in the laboratory. It also studied the detection performance, stability and SGS method of different objects the accuracy of the measurement results.

Reaktor Serba Guna-G.A. Siwabessy (RSG-GAS reactor) is a pool type research reactor, located in Serpong village, Indonesia. For safety of RSG-GAS reactor, the maintenance level criterion of System, Structure and Component (SSC) can be carried out by assessing on occurrence likelihood of a potential risks due to ageing degradation and a Risk Priority Number (RPN) value for assigning maintenance criterion, respectively. The objective of present study is to propose using the Failure Mode and Effects Analysis (FMEA) for assigning the maintenance level criterion of SSC and implementing on JE01-AP01 primary pump within a RSG-GAS reactor. In this research paper, SSC screening and failure based maintenance methodology is identified and classified into suitable classes at radar diagram. Results show that SSC can be prioritized based on failure analysis so that maintenance level criterion for SSC can be determined. On the implemented study, preventive maintenance can be performed to JE01-AP01 primary pump because of its RPN value 270.

In new generation PWR the annular fuel has been proposed as one of the options to achieve higher power density, larger safety margin and reduced electricity generation cost. In the current work, RELAP5 code is used to compare the thermal hydraulic parameters for both solid fuel and internally and externally cooled annular fuel in a core of a PWR. MCNP6 code is used to evaluate the neutronic design and basic safety parameters of the annular fuel. To accomplish this goal, RELAP5 input files for both solid and annular fuels are developed. In these files, a 13 · 13 array annular fuel design is used while the 17 · 17 standard array design is used for the solid fuel. A 100% core power, steady state normal operation is assumed in the current investigation. Also, MCNP6 code input files for both fuels are prepared. It is found that annular fuel has lower peak fuel temperature than the standard solid fuel, which is an important advantage of the annular fuel rather than the solid one. Also, comparisons were performed for reactivity feedback coefficients of the two fuel types at BOC. Burnup calculations were performed to study the energy conversion capability of the annular fuel as well as rim effects.

Gadolinium is mixed with nuclear fuel for extended burnup, increased reactor cycle Lengths, and in-out core refueling schemes. The purpose of this work is to investigate the effect of Gadolinium on neutronic parameters. A comprehensive analysis of different fuel assemblies bearing gadolinia with different concentration and different number of gadolinia rods was carried out. The EPR fuel assemblies were chosen in this study. The fuel assemblies are of seven different types, each assembly has unique design characteristics in terms of enrichment, number of gadolinia rods and gadolinium concentration. The calculations were achieved using MCNP6 code and with ENDF/B-VII library. A fine mesh tally was superimposed on the geometry to illustrate flux distribution in the whole assembly and its change with burnup. The variation of reactivity and isotopic composition for each region of the assembly with burnup and its influence on flux distribution was studied. The results showed that the presence of gadolinium greatly affects the power distribution. It causes some skewness in axial power shape towards the top of the assembly, the assembly which has largest number of gadolinia rods and the lowest enrichment has the largest skewness of power distribution at BOC. At EOC the flux and axial power have a double hump shape due to the buildup of gadolinium isotopes and the large decrease in reactivity with burnup.

The effect of burnable poisons on neutronic parameters of PWR is an important issue in nuclear fuel design. Burnable poisons are used to control the reactivity of the core and to improve fuel utilization. It classified to Burnable Poison Rods (BPRs) and Integral Burnable Absorbers (IBAs). This work focuses mainly on Burnable Poison Rods. The main purpose with this paper is to study and analyze the effect of different materials of Burnable Poison Rods (BPRs). The investigation was performed using MCNP6 code together with the Evaluated Nuclear Data Files, (ENDF/B)-VII.1. The investigation included study of the effect of: presence of BPRs and the changes of BPRs number. The calculations were carried out for two types of BPRs; Pyrex and WABA rods. The reactivity and radial power distribution and its variations vs. burnup were carried out up to50 Gwd/MTU. The results evidence that at BOC, the Pyrex and WABA have large compensation of reactivity; Pyrex has more negative reactivity than WABA. Lower power is obtained at the pin near the poisons rods due to large absorption cross section of boron material. The maximum pin power was located at the edge of the assembly due to the absorbing effect of BPRs.