Obrigheim (Germany)

Map of Obrigheim

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PWR 340 MW constructed by KWU; grid connection 1968, shut-down in 2005

Facilities in Obrigheim

plantreactor typconstruction startoperation startshut down

The Bundesamt für Strahlenschutz (BfS) announced that the npp Obrigheim will be shut down soon because it has reached the end of its planned operating period.


In 2004 six events rated INES 0 occured according to the BfS annual report.


In 2003 six events rated INES 0 occured according to the BfS annual report.


The chief nuclear regulator in the state of Baden-Wuertemberg allowed the 357-MW Obrigheim PWR to restart, rejecting claims by critics that pressure vessel embrittlement should have forced decommissioning of the 27-year-old unit.
A conservative estimate for the Obrigheim vessel's resistance to pressurized thermal shock - which could have led to calculation of a higher RT-NDT - was not justified, the lawyers said, since such an estimate must be based on assumption of "faulty plating" in the area of the beltline weld. But the plating at Obrigheim "is intact", the study pointed out.


A dossier of internal documents from German safety agencies, provided to Nucleonics Week, suggest that there are some problems and uncertainties in the data base upon which Baden-Wuerttemberg is making its decision about the health of the Obrigheim vesselectrical
Documents from Gesellschaft fuer Anlagen- und Reaktorsicherheit mbH (GRS) from last month note that five samples of the Obrigheim vessel were taken and that none of these were suitable or judged to be "representative" of the material in the vessel's beltline weld. Two of the samples were not irradiated. A third sample, designated by GRS as "assumed to be representative" was prepared 18 months after the circumferential weld was made and is problematic because the amount of chromium in the sample was less than that in the vesselectrical A fourth sample, made for the Stade PWR, is described by GRS as "similar" but not "representative".
The fifth sample, described by GRS as "assumed to be representative", was collected 13 years after the weld was made, and has provided only a "small amount" of reliable data for analysis.
On the basis of the samples available, however, the Obrigheim owner consortium, led by Energie-Versorgung-Schwaben AG (EVS) and Badenwerk AG, and its consultants, has concluded that the Obrigheim vessel would have to be cooled from an operating temperature of 300 ° C to about 80°C before the vessel material is transformed from a ductile to a brittle state. During a loss-of-coolant accident (LOCA) scenario, such a low temperature would not likely be reached during emergency core cooling.
The U.S. NRC Regulatory Guide for determining a conservative value for NDT temperature, based on known variables such as weld copper and nickel content and core flux led to calculation of a conservative estimate for NDT temperature of about 200 ° C, Hirsch (Greenpeace) said.
With an NDT temperature of 200 ° C, "it is not possible to assure the safety of the reactor under German law", Hirsch said. Calculations carried out by GRS and Obrigheim-owning utilities, reported in internal documents from the Reaktorsicherheitskommission (RSK), show that during LOCA sequences, emergency core cooling can reduce the temperature of the vessel to about 150 ° C - far less than the NDT temperature Hirsch calculated.
After Greenpeace raised the issue in a letter to regulators dated October 21, the decision on restarting the reactor was postponed for several days. During that time, regulators will consider how publicly to address the questions about the vessel's integrity.


Superior Administrative Court of Baden Wuertemberg announced that the commercial operation license for the plant, awarded by the state in 1992 was not based on sufficient examination of safety issues. In October 1992 Obrigheim got a final operating license on condition that a list of safety measures are investigated, especially RPV embrittlement. In April 1995 the Court lifted the conditional operating license, but ecxperts in the regulatory agency do not belive that the state of the RPV will justify a pemature shutdown.