Band 90, Heft 5

In the essential service water system (SEC) of the nuclear power plants (NPPs), pressure surges (water hammer) are possible due to the operation of components such as valves, pumps, and heat exchangers, which can cause damage to the pipeline. The main focus of this study is to predict the occurrence of water hammer and to optimize the operation of these components in order to minimize pressure surges to the greatest extent possible. This paper focuses on the SEC of a typical pressurized water reactor (PWR), by employing a thermal-hydraulic system code to model the operation of the SEC. The accuracy of the model is verified by comparing the experimental results with those from the calculations. Through the sensitivity analysis of the time step and the control volume length, the minimum time step is selected as 0.001 to predict the pressure peak under actual working conditions. Two water hammer types are analyzed: 1) void-induced water hammer; 2) rapid operation of the valve-induced water hammer. Void-induced water hammer, the pressure peaks are moderate, and the pressure waves propagate continuously, gradually diminish. In contrast, rapid valve closure generates higher pressure peaks. Upon reaching air-containing section, the pressure waves caused by the valve closure can superimpose, resulting in irregular pressure fluctuations. By tracking pressure and flow variations, we can study the variation process of the water hammer phenomenon better, and provide a reference for the operation and control of SECs in the PWR, and the future research.

In the present study, nanofluids and helical annular tube are investigated as an enhancement technique of heat transfer. Heat transfer and laminar behaviors of two different metal nanoparticles oxide copper oxide and Aluminum oxide (36 nm) and CuO (29 nm), nanofluids flow inside an annular coiled tube heat exchanger (ACTHE) with a boundary condition of constant heat flux which is numerically studied and predicted to assess or evaluate their improvement over the water base fluid. The simulation model covers many volumes of nanoparticles concentration in the range 1.0–6.0 % and flow rate of its mass within range 0.025–0.125 kg/s. Numerical results indicate that a substantial heat transfer improvement is fulfilled by each water based CuO and Al 2 O 3 nanofluids, 46.8 % and 17.7 %, respectively. At the same Reynolds number, an increase of pressure drop and convective heat transfer is observed with increasing particle volumetrically concentration of the nanofluids. The general performance of the two increased heat transfer techniques utilized, and therefore the two nanofluids are assessed employing performance index of thermo-hydrodynamic. Moreover, typical correlations for spiral circular tubes for studying mean friction factor and heat transfer during laminar flow condition like the correlations derived by Mori, Y., and Nakayama, W. (1965). Study on forced convective heat transfer in curved pipes (1st report, laminar region). Int J Heat Mass Trans 8: 67–82 and Manlapaz, R.L, and Churchill, S.W. (1981). Fully-developed laminar convection from a helical-coil. Chem Eng Commun 9:185–200, respectively, are correct for water and therefore the considered nanofluids with very small nanoparticle feeds the coolant inside ACTHE.

Gadolinia (Gd 2 O 3 ), known for its high neutron capture cross-section, is used in nuclear reactors to regulate reactivity and extend reactor life by absorbing excess neutrons. This study uses the OpenMC, an open-source Monte Carlo simulation code, to evaluate the use of Erbia (Er 2 O 3 ) as a potential supplement for Gadolinia in VVER-1200 reactors. Varying fractions of Er 2 O 3 (1 %, 3 %, and 5 %) were compared with the standard 5 % Gd 2 O 3 . Using ENDF/B-VIII.0 nuclear data library, criticality, reactivity, depletion up to 60 MW d/kgHM, pin power distribution at 0 MW d/kgHM and 40 MW d/kgHM, effects of control rods were analysed. Additionally, the effect of control rods, fuel and moderator temperature coefficients, and the effect of boron concentration variation have been observed. The results show that different variations of Er 2 O 3 achieve similar reactivity control and power distribution as current designs, although Er 2 O 3 provide excess reactivity at the start of the cycle, it maintains a relatively balanced power among fuel pins. Actinide production was also comparable to that of the reference 5 % Gd 2 O 3  model.

Improving the level of situational awareness (SA) can effectively decrease the occurrence of human errors in nuclear power plants (NPPs). However, a significant gap exists in systematically identifying the specific information require to build SA and in quantifying the key influencing factors that influence information acquisition. To address this gap, this study proposed a mixed-methods framework to uncover SA requirements in the context of the water supply deaerator system (ADG). Firstly, this study employed Goal-Directed Task Analysis (GDTA) through interviews with experienced operators to establish a hierarchical model of SA information needs. This model was used to reveal the operator’s SA information requirement during the operation of ADG system, and the information was divided into three levels. Subsequently, the combination of the entropy weight and the coefficient of variation methods were used to determine the relative importance of SA influencing factors. This research contributes a detailed, operationalized SA information model for a specific NPPs system, and it provides an empirically-grounded basis for the targeted optimization of human-computer interface (HCI) design and operator training programs, ultimately enhancing NPPs safety.

Spent nuclear fuel discharged from a nuclear power reactor is stored in a wet pool for approximately 7–10 years to reduce decay heat. Then, it transferred for processing or to a dry storage waiting for final disposal. Dual-purpose metal casks have proven to be a good technical, economic, safe, and flexible solution that is adaptable to long term spent fuel storage. This research work explores the critical aspects of safety and security related to the dry storage of Boiling Water Reactor (BWR) spent fuel assemblies cooled down for 10 years were loaded in the TN-68 dual purpose casks. The source term of the spent fuel was calculated using ORIGEN- ART/SCALE code, which used as input for MCNP5 code for dose rate calculations around the cask. The radioactive source term will be compared with the safe dose rate limits according to the recommendations of 10 CFR Part72. Additionally, the security measures and preparedness of the proposed site will be monitored and analyzed to fulfill the nuclear safety, security and safeguards objectives in normal storage and in case of attack from terrorism or malicious acts. Surveillance ground radars system with large microwave perpendicular detection field equipped with long-range laser infrared cameras used formonitoring and detecting any intrusion to the dry fuel cask storage site. Onsite cranes used for the movement and handling of the casks will be protected by using motion alarm cameras. For security system evaluation we used the Estimate of Adversary Sequence Interruption (EASI) model.