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The OECD/NEA - US/NRC
PWR Main Steam-Line Break Benchmark Summar

Scope / Objective

This benchmark incorporates full 3D modelling of the reactor core into system transient codes for "best-estimate" simulations of the interactions between reactor core behaviour and plant dynamics and their testing on a number of transients of importance for plant behaviour and safety analysis. This includes verifying the capability of codes to analyse complex transients with coupled core-plant interactions, to fully test the 3D-neutronics/thermal-hydraulics coupling, and to evaluate discrepancies between predictions of coupled codes in best-estimate transient simulations.

Description of the problem

The benchmark is based on a well-defined problem concerning a PWR Main Steam Line Break (MSLB), which may occur as a consequence of the rupture of one steam-line upstream of the main steam isolation valves. This event is characterised by significant space-time effects in the core caused by asymmetric cooling and an assumed stuck-out control rod during reactor trip. It is based on reference design and data from the Three Mile Island Unit 1 Nuclear Power Plant (TMI-1). It includes a description of the event sequence with set points of all activated system functions and typical plant conditions during the transient.

Methodology

It consists of three exercises:
1. Point kinetics simulation to test the primary and secondary system model responses
2. Coupled 3D neutronics / core thermal-hydraulics response evaluation using inlet and outlet core transient boundary conditions
3. Best-estimate coupled core – plant transient modelling

The first two exercises have helped tuning the models in the different codes in order to ensure they all solve the same problem and parametric studies and scenarios were developed to help understanding the source of uncertainties. Suite of statistical methods has been applied to analyse code-to-code comparisons involving different type of data – single values, 1-D and 2-D distributions, and time histories. The statistical methods have been modified to analyse correctly relative normalized parameters.

Sponsors / Participants

The exercise is co-organised by the OECD/NEA Nuclear Science Committee and the Committee on the Safety of Nuclear Installations and the US Nuclear Regulatory Commission. It has involved about 70 experts from 15 countries representing 30 organisations. It has brought together specialists in neutronics and thermal-hydraulics from universities, research centres, utilities, engineering companies and vendors. They have worked together on this project. It is co-ordinated by the Penn State University Nuclear Engineering Program Team.

Conclusions and Recommendations

This exercise has shown:

References

Special Session on MSLB at the ANS Annual Meeting, Milwaukee, 18-19 June 2001, List of papers to be published in "Progress in Nuclear Energy".


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Last reviewed: 8 December 2011