atw - July 2017

Avoid Disruption of "Disorderly" Withdrawal from Euratom
Elements of Severe Accident Management
Analysis for Main Control Room Fire Scenario
Nuclear Power Plants: 2016 atw Compact Statistics

Nuclear Industry Calls on UK to Avoid Disruption of ‘Disorderly’ Withdrawal from Euratom


The UK will need to set priorities for Brexit talks if it is to avoid disruption in the nuclear sector and the possibility of a disorderly withdrawal from the Euratom Treaty affecting ambitious plans to build new nuclear reactors, Tom Greatrex, chief executive of the London-based Nuclear Industry Association (NIA), said. Mr Greatrex, a former Labour MP and shadow energy minister, warned that a lack of prioritisation in Brexit talks could lead to problems related to moving nuclear-purpose components and difficulties collaborating with counties in nuclear R&D projects with significant economic, industrial and scientific impact.

Decommissioning and Environmental Remediation Scenario Development for Fukushima Daiichi

Hideki Kawamura, Shoko Yashio and Ian G. McKinley

Although the general approach to reactor decommissioning is well established, there is no direct precedent for managing the 6 units of the Fukushima Daiichi nuclear power plant. Apart from damaged reactors, challenges include extensive contamination of the entire reactor site and a huge tank farm currently storing contaminated cooling water. In order to move forward with planning decommissioning, it is important to decide on the desired end state of the site and understand the impact on such a decision on the costs, hazards and environmental impact of the project. A decommissioning roadmap and reference dismantling concept provide a basis for short-term planning, but the potential for technological optimisation should be carefully considered.

The Countdown for the Negotiations on the Exit of Great Britain from the EU and Euratom has begun

Ulrike Feldmann

On 29 March 2017 the official letter from the United Kingdom to the President of the EU Council was presented to inform the European Council of its intention to withdraw from the European Union (EU). The period of 2 years in Article 50 of the EU Treaty provided for the exit negotiations has thus begun to run. In the letter to the President of the Council, the UK Government expressly declares its intention to withdraw from the EU and from the Euratom Treaty (EAV). Thus the controversy about the conjunction of the withdrawal from the EU and Euratom has become obsolete.

The Five Essential (´Key`) Elements of Severe Accident Management – To be Developed as Part of a SAMG Industry Standard

George Vayssier

The Fukushima-Daiichi accident has caused a renewed interest in tools and guidelines to mitigate severe accidents. Notably, industry approaches have been reviewed and features added from the lessons learned. The various severe accident management approaches vary considerably: they have different measures, different priorities for the various actions, different staff responsibilities and different sorts of communication to the off-site authorities. It appears that there is no common basis from which the approaches have been developed. In this paper, the five elements are treated which the author considers essential for proper tools to terminate severe accidents and mitigate their consequences. These five elements should be trained in well-developed drills/exercises, involving all functions of accident management. An industrial standard to define a minimum common basis, to which individual approaches should adhere and so decrease the large scatter in these approaches present now.

Uncertainty Analysis for Parameters of CFAST in the Main Control Room Fire Scenario

Wanhong Wang, Yun Guo and Changhong Peng

The fire accident is one of important initial events in the nuclear power plant. Moreover, the fire development process is extremely difficult and complex to predict accurately. As a result, the plant internal fire accidents have become one of the most realistic threat on the safety of the nuclear power plants. The main control room contains all the control and monitoring equipment that operators need. Once it is on fire, hostile environments would greatly impact on the safety of human operations. Therefore, fire probability safety analysis on the main control room has become a significant task. By using CFAST and Monte Carlo sampling method as a tool for fire modeling to simulate main control room on fire, we can examine uncertainty analysis for the important parameters of CFAST.

Transient Subchannel Simulation of Sodium Boiling in a 37 Rods Bundle with Semi Implicit and Full Implicit Algorithms

Hamed Moslehi Azad and A.S.Shirani

Thermal hydraulic analysis of sodium boiling in fuel assemblies is an important issue in safety of sodium cooled reactors and subchannel method is an efficient approach in transient two phase flow analyses. Almost all of the subchannel codes which use two-fluid model in two phase flow analysis, are based on semi implicit algorithm. With the full implicit method it is possible to use larger time steps. In order to compare the semi implicit algorithm with full implicit algorithm, two transient subchannel numerical programs which one is based on semi implicit algorithm and the other is based on full implicit algorithm have been written in FORTRAN in this work for simulation of transients in sodium cooled Kompakter-Natriumsiede-Kreislauf (KNS) at the former Kernforschungszentrum Karlsruhe (KfK) in Germany.

Ultrafast X-ray Tomography for Two-phase Flow Analysis in Centrifugal Pumps

Katharina Amend and Markus Klein

The paper presents a three-dimensional numerical simulation for water running down inclined surfaces using OpenFOAM. This research project aims at developing a CFD model to describe the run down behavior of liquids and the resulting wash down of fission products on surfaces in the reactor containment. An empirical contact angle model with wetted history is introduced as well as a filtered randomized initial contact angle field. Simulation results are in good agreement with the experiments.

Heat Transfer by Long Closed Two-Phase Thermosiphons

Claudia Graß, Rudi Kulenovic and Jörg Starflinger

The removal of decay heat from spent fuel pools is presently realized by active cooling systems. In case of a station black out, a passive heat removal based on closed two-phase thermosiphons can contribute to the power plant safety. In this paper, the basic laboratory setup for closed two-phase thermosiphons and first experimental results are presented. Depending on the driving temperature difference and the heat input, steady-state and pulsating operation of the thermosiphons are investigated.

Nuclear Power Plants: 2016 atw Compact Statistics


At the end of the last year 2016, nuclear power plants were operating in 31 countries worldwide. In total, 450 nuclear power plants were operating on the key date. This means that the number raised by 8 units compared to the previous year’s number on 31 December 2015 and is the highest ever. 10 units started operation, 2 units stopped operation. Installed nuclear capacity is now also the highest that it has ever been at 421 gigawatts electrical gross. 58 plants in 15 countries were under construction. In addition, there are about 125 nuclear power plant units in 25 countries worldwide.

As US Breathes New Life into Nuclear, Switzerland Says Adieu, Japan Hello Again

John Shepherd

The US has given its strongest signal to date, since President Donald Trump moved into the Oval office at the start of the year, that nuclear will have a strong role to play in the administration’s energy policy. In May, Switzerland confirmed that it would follow the lead of neighbouring Germany in beginning a phase-out of nuclear power as part of a revised energy strategy. Japan’s actual actions stand in marked contrast to those of Switzerland – and Germany. Instead of turning its back on nuclear, Japan took a sensible, long-term pragmatic view of its energy needs into the future with restarts of nuclear power plants.


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