atw - October 2015

German Repository Engineering in International Markets
Activity Calculation of Core Components
Control Rod Reactivity Determination of a MTR Research Reactor
Assessment for Follow-up Liability in the Nuclear Sector
Workshop: Preserving Competence in Nuclear Technology

“As a German Citizen, I Am Curious as to How Grid Stability Will Be Maintained”

NucNet

With Germany pushing ahead with plans to phase out nuclear energy by 2020, Ralf Güldner, president of the German Atomic Forum, talks to NucNet about the future of nuclear, continuing efforts to open a high-level waste repository, and potential economic problems caused by high levels of uncertainty in the country’s power market.

German Repository Engineering in Inter­national Markets – DBE TECHNOLOGY GmbH Success Story

Enrique Biurrun, Thilo v. Berlepsch and Jürgen Krone

DBE TECHNOLOGY GmbH was founded in 2000 as a spin-off from the Technology and Development Division of DBE, the German Company for the Construction and Operation of Repositories for Wastes. Today, 15 years later, DBE TECHNOLOGY GmbH can draw upon a tremendous amount of experience and knowledge, which goes far beyond the planning and operaation of Deep Geologic Repositories and the development of technologies for the disposal of radio­active waste. The capabilities of DBE TECHNOLOGY GmbH are presented by leading through its history, describing its roots and highlighting main projects the company has been involved in.

Determination of Representative Nitrogen Contents for the Activity Calculation of Core Components with Respect to the C-14 Activity

Philipp Kruse, Frank Hüttner and Peter-Wilhelm Phlippen

For the final repository Konrad during operating and decommissioning phase, ten radionuclides and two radionuclide groups are restricted regarding their maximum storable activity quantities. One of the ten relevant radionuclides is C-14. The determination of the C-14 activities within activation calculations is currently performed with conservative assumptions. With the results of the presented analysis a method for a realistic determination of representative C-14 contents of irradiated steels is available now. The relevant N-14 contents as a source for the C-14 amount are lower than previously estimated.

Control Rod Reactivity Worth Determination of a Typical MTR Research Reactor

M. Rizwan, S. S. Raza and R. Khan

The safe and reliable utilization of research reactor demands the possible accurate information of control rod (CR) worths. The criticality positions of the control rods changes with time due to build up fission products. It is therefore important to determine the reactivity worth of control rods. The aim of this article is to estimate the reactivity worth of controls rods in the equilibrium core of a Materials Testing Reactor (MTR). A deterministic model of the reactor core was developed and confirmed against the reference results of excess reactivity, shutdown margin and combined control rod reactivity worth using the combination of WIMS/D4 and CITATION computer codes.

A Desire, if Fulfilled ... Order for Reference in Case of the Prohibition for Transhipment of Nuclear Fuel

Ulrike Feldmann

Three companies appealed against the ‘Bremischen Hafengesetz’ (Bremen Port Act) before the ‘Verwaltungsgericht Bremen’ (Bremen Adminis­trative Court) regarding the ban on nuclear fuel tran­ship­ment. The court is convinced that the act is unconstitutional and referred the case to the Bundesverfassungsgericht (Federal Constitutional Court).

New Law on Extension of Liability for Nuclear Obligations Unconstitutional

Herbert Posser

The provisions of the draft law are highly relevant with regard to fundamental rights and do not stand up to the required proportionality scrutiny. The following fundamental rights are affected: Article 14 (1), (2) GG (German Basic Law): guaranteed right to property; Article 12 (1) GG: freedom of occupation; Article 9 (1) GG: freedom of association; Article 2 (1) GG: general freedom of action; Article 3 (1) GG: equality before the law. In view of the German system of contingency reserves, which is tried and tested in practice and which has been working for 40 years without objections or failure, the envisaged provisions are not necessary, to begin with. If the draft law such as it is today became actual legislation, this would evidently be contrary to the constitution.

AMNT 2015: E.ON’s Strategy: Managing Regulation and Political Uncertainty

Leonhard Birnbaum

Energy turnarounds are currently going on in several countries and many countries already underwent energy turnarounds. From a global perspective we see a competition of energy turn­arounds in e.g. Germany, the US, Spain or UK: Which energy concept will contribute best regarding the future of a country resp. a region? Speed and direction of an energy turnaround is in the long run determined by technological innovation and by the demand of the energy customers. Consequently, energy policy in Europe and in Germany should now switch to a macro-management. The nuclear industry can take an active role in all energy turnarounds.

AMNT 2015: Workshop: Preserving Competence in Nuclear Technology

Wolfgang Steinwarz

On the 17th workshop Preserving Competence in Nuclear Technology 21 young scientists presented the scientific results from their thesis work for a diploma, mastership or a PhD covering a broad spectrum of technical areas. This demonstrated again the strong engagement of the younger gen­eration as part of the German nuclear society. Prof. Dr.-Ing. Eckart Laurin, Prof. Dr.-Ing. Marco K. Koch and Dr.-Ing. Wolfgang Steinwarz as members of the jury assessed the written compacts and the oral presentations to award the Siempelkamp Competence Price 2015 to Tobias Seidel from Helmholtz-Zentrum Dresden- Rossendorf e.V.

AMNT 2015: Direct Condensation and Entrainment Steam Experiments at the Topflow-Denise Facility

Tobias Seidel

In a hypothetical Small Break Loss of Coolant Accident (SB-LOCA) in a Pressurized Water Reactor (PWR), the Reactor Pressure Vessel wall (RPV) may be exposed to thermal stress, since the Emergency Core Cooling System (ECCS) injects cold water. The loads on the primary loop and RPV walls are determined by mixing processes with the surrounding hot water and by the condensation of steam on the surface. For the development and validation of CFD-models, experiments have to meet a high standard of reproducibility, measurement certainty and temporal and local resolution. The pressure tank technology of the TOPFLOW facility allows conducting such experiments at reasonable effort.

AMNT 2015: Experiments on the Dryout Behavior of Stratified Debris Beds

Simon Leininger, Rudi Kulenovic and Eckart Laurien

In case of a severe accident with loss of coolant and core meltdown a particle bed (debris) can be formed. The removal of decay heat from the debris bed is of prime importance for the bed’s long-term coolability to guarantee the integrity of the RPV. In contrast to previous experiments, the focus is on stratified beds. The experiments have pointed out that the bed’s coolability is significantly affected.

AMNT 2015: Experimental Investigation of High Cycle Thermal Fatigue in a T-Junction Piping System

P. Karthick Selvam, Rudi Kulenovic and Eckart Laurien 

High cycle thermal fatigue damage of structure in the vicinity of T-junction piping systems in nuclear power plants is of importance. Mixing of coolant streams at significant temperature differences causes thermal fluctuations near piping wall leading to gradual thermal degradation. Flow mixing in a T-junction is performed. The determined factors result in bending stresses being imposed on the piping system (‘Banana effect’).

AMNT 2015: Key Topic: Enhanced Safety & Operation Excellence | Radiation Protection

Erik Baumann and Angelika Bohnstedt

Summary report on the Focus Session “Radiation Protection” of the 46th Annual Conference on Nuclear Technology (AMNT 2015) held in Berlin, 5 to 7 May 2015. Other Sessions of AMNT 2015 have been covered in atw 7 and 8 (2015) and will be covered in further issues of atw.

60th year atw: About Decommissioning of Nuclear Facilities

Dieter Brosche, K. Klein and Jürgen Vollradt 

The IAEA organised an International Symposium in 1978, which dealt with the main aspects of decommissioning nuclear plants. Sufficient practical experiences and elaborated decommissioning concepts and techniques are already available. Unsolvable problems or only solvable with tremendous efforts of time and expenses are according to the opinion of experts not to be expected. Important statements concern above all the dose load of the decom­missioning staff and the costs for decommissioning.

Why Switzerland’s ‘Summer Break’ from Nuclear was a Wake-up Call for Us All

John Shepherd

The summertime Alpine sunshine in Switzerland this year smiled on all of those who want to halt the use of nuclear energy in the country by granting their wishes … at least for a few weeks. An unplanned outage at the country’s single unit Gösgen nuclear plant meant electricity generation at all of Switzerland’s five nuclear reactor units ceased unexpectedly in August. What happened at Gösgen did not have any impact on safety or the environment. But the background leading up to this unusual scenario and consequences for system stability and safety of supply are worth considering in greater detail.

 

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