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Bharat Reactor Analysis for Hydraulics, Malfunctions, and Accidents (ब्रह्मा२३) (BRAHMA23)
Bharat Reactor Analysis for Hydraulics, Malfunctions, and Accidents (ब्रह्मा२३) (BRAHMA23)

  • What is Natural Circulation?

    Natural circulation is a passive heat removal mechanism. In this mechanism, the working fluid flow within a closed loop is driven entirely by the buoyancy force generated from the density difference between the hot and cold sections, without relying on any mechanical pump. This mechanism forms the core support for the passive safety designs of multiple types of nuclear reactor concepts, including small modular reactors (SMRs), pressurized water reactors, boiling water reactors (BWRs), as well as liquid metal cooling systems and molten salt cooling systems. To ensure the safe operation and obtain licensing for these reactor types, it is necessary to accurately predict the steady-state flow rate, axial temperature, and void fraction distribution. Among these tasks, the most critical one is to accurately forecast the onset of hydrodynamic instability.

Why Stability Matters

Vijayan et al. (2019) documents two experimentally distinct instability mechanisms in two-phase natural circulation loops. Type I instability is gravity-dominated, triggered under conditions of low power and low quality, and manifests as an exponentially diverging flow excursion (the Ledinegg instability) or an ultra-low-frequency oscillation. Type II instability is friction-dominated, caused by the finite transit time of density waves between the heater and the riser section. This forms a regenerative feedback loop that produces self-sustained oscillations with frequencies ranging from 0.1 to 2 hertz. The two mechanisms are not mutually exclusive. As the loop power increases, the loop will sequentially pass through a stable region, a Type I unstable region, a restabilised region, and then enter a Type II unstable region. This evolutionary sequence cannot be captured by any single steady-state correlation.

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Why ब्रह्मा२३/BRAHMA23  

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Industry-Scale Limitations

Established industrial codes offer validated simulation capability, but their scale makes them cumbersome for rapid research iteration and exploratory analysis.


Project Planning
Built for PYTHON, First of Its Kind

ब्रह्मा२३/BRAHMA23 closes this gap as the first Python-based suite of its kind, with a modular and fully transparent architecture designed for extensibility.


Site Management
Traceable, Efficient, Reliable

Every equation is directly traceable to published literature, offering a more efficient alternative for natural circulation stability research and test-loop design.


Suite Overview

This modular Python code suite, ब्रह्मा२३/BRAHMA23, contains 8 independent modules for analysing two-phase natural circulation loops (TPNCL) in nuclear reactor systems. It covers a complete analysis chain ranging from basic steady-state loop characterization to full time-domain reactor transient simulation. All physical models follow the notation and equation numbering of Vijayan et al. (2019), enabling direct cross-reference between the code and the source textbook.