Analysis with TRACE Code of PKL-III Test F 1.2

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Publication Information

Manuscript Completed: January 2013
Date Published: February 2013

Prepared by:
J.L. Munoz-Cobo, S. Chiva, A. Escrivá

Instituto de Ingenierίa Energética
Univesitat Politécnica de Valéncia
Camino de Vera s/n. 46022 Valéncia

A. Calvo, NRC Project Manager

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

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

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The goal of this report is to explain the main results obtained in the simulations performed with the consolidated code TRACE for the OCDE TEST PKL-III F 1.2. The transient was produced by a set of successive extractions of refrigerant performed through the bottom of the vessel of the PKL-III facility in Germany, after each extraction phase no extraction was performed during a certain time, this no-extraction time was long enough to reach a quasi-stationary state so the new natural circulation conditions could be experimentally observed. Therefore, the goal of this test is to see how the inventory of refrigerant in the primary circuit affects to the natural circulation conditions in the primary circuit and when the natural circulation stops. The experiment had two different parts during, the first one were performed a set of extraction of refrigerant followed by no extraction intervals, until a minimum inventory was reached, during this set of extractions and the quasi-stationary periods that followed to each extraction period, the power was maintained constant. The second step of the experiment consisted in a set of injections symmetrical to the extractions, which refilled again the primary system although the total number of refilling steps was smaller than the number of the extractions and, therefore, the initial conditions were not achieved. The total duration of the experiment was 90000 s. After each extraction step the relief valves of the secondary system were manipulated in order to maintain constant the pressure in the primary system, this was done manually by the operator. In the code simulation, we simulate with TRACE the first 40000 s of the experiment until the natural circulation was completely stopped and the system enters in reflux condenser conditions.

The TRACE code was able to predict correctly the natural circulation mass flow rate along time. We note that the natural circulation mass flow rate at the beginning of the transient is 1.21 kg/s that is correctly predicted by TRACE, then after several successive extractions steps this mass flow rate increases reaching a maximum value of 3 kg/s. This value is also correctly predicted by the TRACE code. When the inventory is too low the natural circulation start to diminish progressively with the successive extractions until it stop.

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