Natural circulation and stability performance of BWRs (NACUSP)

Natural circulation characteristics at low pressure/low power have been studied by performing experimental investigations and numerical simulations. The PANDA large-scale facility was used to provide valuable, high quality data on natural circulation characteristics as a function of several parameters and for a wide range of operating conditions. The new experimental data allow for testing and improving the capabilities of the thermal-hydraulic computer codes to be used for treating natural circulation loops in a range with increased attention. This paper presents a synthesis of a part of the results obtained within the EU-Project NACUSP “natural circulation and stability performance of boiling water reactors.” It does so by using the experimental results produced in PANDA and by showing some examples of numerical simulations performed with the thermal-hydraulic code ATHLET.

Section: Nd Groupsupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Natural Circulation Characteristics at Low-Pressure Conditions through PANDA Experiments and ATHLET Simulations

Paladino

Huggenberger

Schäfer

2008

“…One of its main aims is understanding the physics of the phenomena involved during the startup phase of natural-circulation-cooled BWRs, providing a large experimental database and validating state-of-the-art thermal-hydraulic codes in the low-pressure low-power operational region of these reactors [11].…”

Section: Inadvertent and Induced Bwr Instabilitiesmentioning

confidence: 99%

Analyses of Instability Events in the Peach Bottom-2 BWR Using Thermal-Hydraulic and 3D Neutron Kinetic Coupled Codes Technique

Costa

Petruzzi

D'Auria

et al. 2008

Boiling water reactor (BWR) instabilities may occur when, starting from a stable operating condition, changes in system parameters bring the reactor towards an unstable region. In order to design more stable and safer core configurations, experimental and theoretical studies about BWR stability have been performed to characterise the phenomenon and to predict the conditions for its occurrence. In this work, contributions to the study of BWR instability phenomena are presented. The RELAP5/MOD3.3 thermalhydraulic (TH) system code and the PARCS-2.4 3D neutron kinetic (NK) code were coupled to simulate BWR transients. Different algorithms were used to calculate the decay ratio (DR) and the natural frequency (NF) from the power oscillation predicted by the transient calculations as two typical parameters used to provide a quantitative description of instabilities. The validation of the code model set up for the Peach Bottom Unit 2 BWR plant is performed against low-flow stability tests (LFSTs). The four series of LFST have been performed during the first quarter of 1977 at the end of cycle 2 in Pennsylvania. The tests were intended to measure the reactor core stability margins at the limiting conditions used in design and safety analyses.

“…As such, the operating pressure of the proposed system must be lower than permitted pressure in the containment due to heat transfer requirement, which means the OLPCCS is a system with very low pressure (near to atmosphere pressure). At present, most investigations on the behaviors of the natural circulation under low-pressure conditions were contributing to the studies of either start-up procedures to cross the instability region (Jiang et al [10], van der Hagen and Stekelenburg [11], Manera et al [12], and Kuran et al [13]) or two-phase flow instabilities (Aguirre et al [14], Aritomi et al [15], Van Bragt and van der Hagen [16], Guanghui et al [17], etc.) for the boiling water reactors (BWRs).…”

Section: Introductionmentioning

confidence: 99%

Study on the Behaviors of a Conceptual Passive Containment Cooling System

Wang

Guo

Sui

et al. 2014

The containment is an ultimate and important barrier to mitigate the consequences after the release of mass and energy during such scenarios as loss of coolant accident (LOCA) or main steam line break (MSLB). In this investigation, a passive containment cooling system (PCCS) concept is proposed for a large dry concrete containment. The system is composed of series of heat exchangers, long connecting pipes with relatively large diameter, valves, and a water tank, which is located at the top of the system and serves as the final heat sink. The performance of the system is numerically studied in detail under different conditions. In addition, the influences of condensation heat transfer conditions and containment environment temperature conditions are also studied on the behaviors of the system. The results reveal that four distinct operating stages could be experienced as follows: startup stage, single phase quasisteady stage, flashing speed-up transient stage, and flashing dominated quasisteady operating stage. Furthermore, the mechanisms of system behaviors are thus analyzed. Moreover, the feasibility of the system is also discussed to meet the design purpose for the containment integrity requirement. Considering the passive feature and the compactness of the system, the proposed PCCS is promising for the advanced integral type reactor.