Modelling and simulation of house load operation of HPR1000 NPP

In this paper, the house load operation of the unit is evaluated, taking the third-generation Nuclear Power Plant (NPP) HPR1000 as an example, considering the primary loop, the secondary loop and the entire on-site electrical power systems. The main work of this study is as following: Firstly, acceptance criteria and specific numerical requirements are set out; the simulation result should meet the relevant criteria. Secondly, the Simulink simulation model of the entire system is built in detail, which can be divided into primary loop, secondary loop and on-site electrical power system parts, with emphasis on the simulation modelling of the turbine generator unit. The component models of each part and their corresponding connection relationships of each part are shown and given. Finally, a house load operation simulation is performed, and the result is compared with the acceptance criteria to verify that whether the generator has the ability to transfer to house load operation as designed.

Numerical Simulation of an Out-Vessel Loss of Coolant from the Breeder Primary Loop Due to Large Rupture of Tubes in a Primary Heat Exchanger in the DEMO WCLL Concept

This work presents a thermohydraulic analysis of a postulated accident involving the rupture of the breeder primary cooling loop inside a heat exchanger (once through steam generator). After the detection of the loss of pressure inside the primary loop, a plasma shutdown is actuated with a consequent plasma disruption, isolation of the secondary loop, and shutoff of the pumps in the primary; no other safety counteractions are postulated. The objective of the work is to analyze the pressurization of the primary and secondary sides to show that the accidental overpressure in the two sides of the steam generators is safely accommodated. Furthermore, the effect of the plasma disruption on the FW, in terms of temperatures, should be analyzed. Lastly, the time transients of the pressures and temperatures in the HX and BB for a time span of up to 36 h should be obtained to assess the effect of the decay heat over a long period. A full nodalization of the OTSG was realized together with a simplified nodalization of the whole PHTS BB loop. The code utilized was MELCOR for fusion version 1.8.6. The accident was simulated by activating a flow path which directly connected one section of the primary with the parallel section of the secondary side. It is shown here that the pressures and the temperatures inside the whole PHTS system remain below the safety thresholds for the whole transient.

Small break loss of coolant accident of 200 cm² in cold leg of primary loop of Angra2 nuclear power reactor evaluation

The aim of this paper is evaluated the consequences to ANGRA 2 nuclear power reactor and to identify the flow regimes, the heat transfer modes, and the correlations used by RELAP5/MOD3.2.gama code in ANGRA 2 during the Small-Break Loss-of-Coolant Accident (SBLOCA) with a 200cm2 of rupture area in the cold leg of primary loop. The Chapter 15 of the Final Safety Analysis Report of ANGRA 2 (FSAR-A2) reports this specific kind of accident. The results from this work demonstrated the several flow regimes and heat transfer modes that can be present in the core of ANGRA 2 during the postulated accident. The results obtained for ANGRA 2 nuclear reactor core during the postulated accident were satisfactory when compared with the FSAR-A2. Additionally, the results showed the correct actuation of the ECCS guaranteeing the integrity of the reactor core.

Evaluation of Single Phase Immersion Cooling System for High Performance Server Chassis Using Dielectric Coolants

Along with advancements in microelectronics packaging, the power density of processor units has steadily increased over time. Data center servers equipped for high performance computing (HPC) often use multiple central processing units (CPUs) and graphical processing units (GPUs), thereby resulting in an increased power density, exceeding 1 kW per U. Many data center organizations are evaluating single phase immersion technology as a potential energy and resource saving cooling option. In this work immersion cooling was studied at a power level of 2.7kW/U with a 5U-height immersion cooling tank. Heat generated by a simulated GPU server was transferred to the secondary loop coolant, and then exchanged with the primary loop facility coolant through the heat exchanger. The chiller supply and return temperature and flow rate was controlled for the primary loop. The simulated GPU server chassis was designed to provide thermal power equivalent to a high power density server. Eight simulated power heaters, of which each unit was the size of a GPU chipset, was assembled in the comparable location to a real IT equipment on a 4U server chassis. Power for the GPU simulated chassis was able to support up to 2700 W maximum. Three investigations for this immersion cooling system evaluation were performed through comprehensive testing. The first is to identify the key decision making factor(s) for evaluating the thermal performance of 4 hydrocarbon-based dielectric coolants, including power parametric analysis, transient analysis, power cycling test, and fluid temperature profiling. The second is to develop an optimization strategy for the immersion system thermal performance. The third is to verify the capability of an 1U heat sink to support high density processor units over 300 W per GPU in an immersion cooling solution.

IHSI Effectiveness for Crack Propagation Observed at Hamaoka PLR Piping

Indications of Ultrasonic Testing (UT) of 4 weld joints in Primary Loop Recirculation (PLR) piping in Hamaoka unit-2 had been identified during the 20th outage (2004). Metallurgical investigation after cutting from 2 weld joins had been conducted because of its accessibility etc. The 4 weld joins had been welded at the plant construction (1978), operated and IHSI (Induction Heat Stress Improvement) had been performed during the 1st outage (1979). 25 years passed by until the metallurgical investigation. As a result of the investigation, crack growth retardation by the IHSI was confirmed since crack tip was round and plastically deformed.