Assessment of the Capability of the TRACE Code to Calculate Hydraulic Piping Loads During Fluid Transients (NUREG/IA-0559)

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Publication Information

Manuscript Completed: December 2025
Date Published: April 2026

Prepared by:
José Manuel Mourin Candocia 

Empresarios Agrupados Internacional
Magallanes, 3.  
Madrid 28015 Spain 

A. Hsieh, NRC Project Manager

Division of Systems Analysis
Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

Prepared as part of
The Agreement on Research Participation and Technical Exchange
Under the Thermal-Hydraulic Code Applications and Maintenance Program (CAMP)

Published by:
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

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Abstract

This document assesses TRACE v.5 Patch 9 code for its ability to calculate hydraulic piping loads during fluid transients (i.e., water hammer). Current software for water hammer analysis assumes liquid flow at low Mach numbers and rather limited cavitation.  However, nuclear power plants must also be designed for fluid transients that fall beyond the capabilities of programs commonly used for water hammer analysis because of the appearance of two-phase flow at high speed (in other words, with a Mach number close to or greater than 1). Examples of these special fluid transients are pipe break, safety relief valve discharge and steam pocket collapse. So far, RELAP5 has been the tool commonly used for analyzing these types of fluid transients, but RELAP5 is now being phased out, so a replacement is needed. TRACE is designed to replace RELAP5 for analyzing the transient thermal-hydraulics in nuclear reactors. The aim of this study, then, is to determine if TRACE may be used to calculate the hydraulic loads during fast fluid transients. 

In this study, the TRACE code was used to calculate three representative cases in which significant pipe loads may arise due to the formation and propagation of shock waves: 

1) Shock tube with nitrogen gas 

2) Discharge line of a safety relief valve with steam 

3) Discharge line of a safety relief valve with hot water 

The results for Case 1, 2 and 3 are compared with the analytical solutions. The accuracy of the results relevant to the predicting of hydrodynamic loads are assessed.