The PKL-1 test programme investigated pressurised water reactor (PWR) safety issues and specifically:
- boron dilution accidents and
- loss of residual heat removal in mid-loop operation (during shutdown conditions).
These issues were investigated by means of thermal-hydraulic experiments that will be conducted at the Primarkreislauf-Versuchsanlage (primary coolant loop test facility) PKL. This facility is owned and operated by AREVA NP and is situated in Erlangen, 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 are believed 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:
- Boron dilution events after small-break loss-of-coolant-accidents;
- Loss of residual heat removal during mid-loop operation in closed reactor coolant systems, potentially also leading to boron dilution;
- Loss of residual heat removal during mid-loop operation with open reactor coolant systems.
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:
- Run A: Loss of RHR with RCS filled, initial level mid loop, pressuriser cold;
- Run B: Loss of RHR with RCS filled, initial level mid loop, pressuriser hot.
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.
Belgium, Czech Republic, Finland, France, Germany, Hungary, Italy, Japan, Republic of Korea, Spain, Sweden, Switzerland, United Kingdom, 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 fur Anlagen- und Reaktorsicherheit (GRS) and by AREVA NP.
Project period: January 2004 to May 2007.
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