NEA Primary Coolant Loop Test Facility (PKL-1) Project

The PKL-1 test programme investigated pressurised water reactor (PWR) safety issues and specifically:

These issues were investigated by means of thermal-hydraulic experiments that will be conducted at the Primärkreislauf-Versuchsanlage (primary coolant loop test facility) PKL. This facility is owned and operated by AREVA NP and is situated in Erlengen, Germany.

In the first category of tests – which dealt with inherent boron dilution during a small-break loss-of-coolant accident - the key issue was whether or not there are plant thermal-hydraulic conditions that can produce reactivity insertion into the core, and thus a potential accident situation. The experiments aimed to reproduce different plant and system configurations, especially those that arebelieved to be potentially most serious, thus encompassing an envelope of conservative cases. Where appropriate, measures that can remedy the boron dilution issue were also investigated.

The second category of tests was to assess accident management operations of the primary circuit after a loss of residual heat removal capability during mid-loop operation. Tests with closed reactor circulation system explored safe procedures for re-establishing heat removal and avoiding significant reactivity insertion into the core. Tests with open circulation systems aimed to explore measures for preventing fuel uncoverage and to maximise safety margins provided by different ways of coolant injection.

The test matrix focused inter alia on the following items that are currently receiving great attention within the international reactor safety community:

AREVA NP have for a number of years conducted valuable experiments on reactor thermal-hydraulics in the PKL facility, including earlier experiments carried out in the framework of the SETH Project. Two tests were carried out in 2004 and two in 2005. A workshop covering an analytical exercise with code predictions related to the PKL tests was also conducted in 2005.The tests carried out in 2005 focused on the loss of residual heat removal in three quarter loop operation with the reactor cooling system closed and on the effect of pressuriser temperature on RCS inventory distribution. In particular, two tests were carried out to address the following scenarios:

The three final tests of the current programme were carried out and reported upon in 2006; the project ended with the final meeting in May 2007. A follow-up to the project, PKL-2, is now under way.

Project data

The data abstract is public.


Belgium, Czech Republic, Finland, France, Germany, Hungary, Italy, Japan, Korea, Spain, Sweden, Switzerland, the United Kingdom and the United States.

Safety organisations, research laboratories and industry from fourteen countries are supporting the PKL project. On the German side, the project is supported by the utilities (VGB Power Tech Service GmbH), by the Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) and by AREVA NP.

Project period

January 2004 to May 2007.


USD 1.2 million per year, with German parties covering 50% of this cost.


K. Umminger, B. Schoen, T. Mull, PKL Experiment on loss of Residual Heat Removal under Shutdown conditions in PWR, Paper 6440, 2006 International Congress on Advances in Nuclear Power Plants (ICAPP'06), Reno, NV, USA, 4-8 June 2006.

Related links

Last updated: 21 October 2014