Pressure Vessel Cracking – Aachen Public Conference

Doel & Tihange Follow-up

In 2012 thousands of defects were discovered in the reactor pressure vessel shells of the NPPs Doel-3 and Tihange-2, Belgium.

The reactor pressure vessel (RPV) is the is the central component of a nuclear reactor, – for safe operation of the nuclear power plant throughout service life RPV failure has to be excluded, because safety systems are not designed to cope with RPV failure

The independent interdisciplinary expertise network, INRAG[1], studied the documents on this issue[2][3], which have been published by the Belgian Regulatory Authority FANC[4]. Based on this study INRAG questions the opinion of the operator – which was accepted by the Regulatory Authority – that these defects were manufacture induced and that these defects did not grow during operation. These defects were not observed during acceptance testing after manufacture.

INRAG is not convinced that the reactor pressure vessel structural integrity assessment using an additional shift for the ductile-brittle transition temperature proposed by the operator[5] is conservative. Experimental testing using non-representative sample material as have been performed by the operator Electrabel cannot eliminate the sets of uncertainties concerning the actual material characteristics of the reactor pressure vessels[6].

INRAG recommended in a letter to FANC that these substantive issues be addressed during the regulatory process, which is now in a decisive stage, relating to the potential restart of these reactors.

Because these issues are potentially generalizable, INRAG strongly recommends inspection of all reactor pressure vessels worldwide for unexpected defects outside the weld regions prescribed in the standards for in service inspection. Therefore INRAG will bring their statement to the attention of the IAEA.

 

Public Conference in Aachen, Germany

The StädteRegion Aachen and INRAG will host a public conference on the safety of Belgian Nuclear Power Plants on April 13 and 14, 2018 in Aachen, Germany.

The aim of the event is to inform the affected population and decision-makers in the federal, state and local authorities about the safety significance of cracks in the reactor pressure vessel of the Belgian nuclear power plant Tihange 2 and to intensify the discourse on further operation among the experts. The Friday afternoon is dedicated to detailed technical lectures, while on Saturday laymen understandable general considerations on the topic of monitoring aging reactors are held.

For the detailed technical lectures, the following presentations are planned:

  • The emergce of hydrogen flakes during fabrication of the reactor pressure vessel (Jan Peirs)

  • The problem of hydrogen flakes in the reactor pressure vessel during operation (Walter Bogaerts)

  • The embrittlement of the reactor pressure vessel (Ilse Tweer)

  • The safety of the nuclear power plant Tihange 2 (Manfred Mertins)

  • Documentation and licensing requirements for nuclear power plants (Dieter Majer)

For the public conference on Saturday, April 14, the following presentations are planned:

  • Presentation of the problem and the explanation of safety-related questions (Christoph Pistner)

  • Importance of the reactor pressure vessel, assumptions on its integrity, and experiences in the US (Gregory Jazcko)

  • The importance of hydrogen flakes in the reactor pressure vessel and the difficulty of verifying material integrity (Rene Boonen)

  • Risk management of the Belgian supervisory authority FANC (Wolfgang Renneberg)

  • Possible radiological consequences of a radioactive release for the Aachen region (Nikolaus Müllner).


 

[1] see www.inrag.org

[2] FANC , Doel 3 and Tihange 2 reactor pressure vessels, Provisional evaluation report, January 30, 2013 http://fanc.fgov.be/GED/00000000/3300/3391.pdf

[3] FANC, Doel 3 Tihange reactor pressure vessels, Final evaluation report, May 2013, http://www.fanc.fgov.be/GED/00000000/3400/3429.pdf

[4] FANC: Federal Agency for Nuclear Control

[5] Electrabel, Safety case report: Doel 3 – Reactor Pressure Vessel Assessment, 05/12/2012 http://www.fanc.fgov.be/GED/00000000/3300/3390.pdf

[6] Ilse Tweer, Flawed Reactor Pressure Vessels in Belgian Nuclear Plants Doel-3 and Tihange-2. Some Comments on the FANC Provisional evaluation report (January 30, 2013). March 2013, Commissioned by the Greens/EFA Group in the European Parliament, Brussels, http://www.greens-efa.eu/fileadmin/dam/Documents/Studies/Flawed%20Reactor%20Pressure%20Vessels.pdf