atw - February 2018

_Gas Colled Reactor Development in China
_Severe Accidents Safety Research for Reactor Buildings
_Knowledge Management and TRIZ for Safe Shutdown Capability
_Corrosion Processes of Alloyed Steels in Salt Solutions
_Playing Politics with Nuclear is all Part of the Game

WANO to Increase Focus on New Nuclear as Industry’s Centre of Gravity ShiftsTowards Asia

NucNet

The World Association of Nuclear Operators (WANO) intends to focus more on new nuclear units coming into operation around the world as the “­centre of gravity” in the industry shifts from the US and Europe to the Middle East and Asia. Theorganisation’s chief executive officer, PeterProzesky, told NucNet that new-build projects in China, India, Turkey and the United Arab Emirates are giving WANO the opportunity to make sure those countries start the operational life of their new units “in a very positive way”. In supporting countries with new units beginning operation, WANO is working more closely with the International Atomic Energy Agency (IAEA). One of the IAEA’s tasks is to help emerging nuclear countries develop the infrastructure andcapability they need to have nuclear power as part of their energy mix.

Development of High Temperature Gas Cooled Reactor in China

Wentao Guo and Michael Schorer

High temperature gas cooled reactor (HTGR) is one of the six Generation IV reactor types put forward by Generation IV International Forum (GIF) in 2002. This type of reactor has high outlet temperature. It uses Helium as coolant and graphite asmoderator. Pebble fuel and ceramic reactor core are adopted. Inherit safety, good economy, high generating efficiency are the advantages of HTGR.According to the comprehensive evaluation from the international nuclear community, HTGR hasalready been given the priority to the research and development for commercial use. A demonstration project of the High Temperature Reactor-Pebble-­bed Modules (HTR-PM) in Shidao Bay nuclearpower plant in China is under construction. In this paper, the development history of HTGR in China and the current situation of HTR-PM will be introduced. The experiences from China may be taken as a reference by the international nuclear community.

The Liability According to § 26 of theGermanAtomic Energy Act – A Wallflower?

Christian Raetzke

According to German law, liability for damage caused by radioactivity can arise from several regulations. In most cases, liability under the Paris Convention on Third Party Liability in the Field of Nuclear Energy, which applies in the field of nuclear power, is at the forefront of discussion. According to § 26 of the German Atomic Energy Act, liability is somewhat in the shadow of the Paris Convention. It applies to the handling of radioactivity in medicine, research and industry (e. g. for test emitters) as well as activities involving natural and depleted uranium and nuclear fusion. The article outlines the basic elements of liability under Section 26 of the German Atomic Energy Act, which may become increasingly important in future due to recent developments such as the phasing out of nuclear power in Germany.

Investigation of Conditions Inside theReactor Building Annulus of a PWR Plant of KONVOI Type in Case of Severe Accidents with Increased Containment Leakages

Ivan Bakalov and Martin Sonnenkalb

Improvements of the implemented severe accident management (SAM) concepts have been done in all operating German NPPs after the Fukushima Daiichi accidents following recommendations of the German Reactor Safety Commission (RSK) and as a result of the stress test being performed. The efficiency of newly developed severe accident management guidelines (SAMG) for a PWRKONVOI reference plant related to the mitigation of chal­lenging conditions inside the reactor building (RB) annulus due to increased containment leakages during severe accidents have been assessed. Based on two representative severe accident scenarios the releases of both hydrogen and radionuclides into the RB annulus have been predicted with different boundary conditions. The accident scenarios have been analysed without and with the impact of several SAM measures (already planned or proposed in addition), which turned out to be efficient to mitigate the consequences. The work was done within the frame of a research project financially supported by the Federal Ministry BMUB.

Sensitivity Analysis of MIDAS Tests Using SPACE Code: Effect of Nodalization

Shin Eom, Seung-Jong Oh and Aya Diab

The nodalization sensitivity analysis for the ECCS (Emergency Core Cooling System) bypass phe­nomena was performed using the SPACE (Safety and Performance Analysis CodE) thermal hydraulic analysis computer code. The results of MIDAS (Multi-­dimensional Investigation in Downcomer Annulus Simulation) test were used. The MIDAS test was conducted by the KAERI (Korea Atomic Energy Research Institute) for the performance evaluation of the ECC (Emergency Core Cooling) bypass phenomenon in the DVI (Direct VesselInjection) system. The main aim of this study is to examine the sensitivity of the SPACE code results to the number of thermal hydraulic channels used to model the annulus region in the MIDASexperiment. The numerical model involves three nodalization cases (4, 6, and 12 channels) and the result show that the effect of nodalization on the bypass fraction for the high steam flow rate MIDAS tests is minimal. For computational efficiency, a 4 channel representation is recommended for the SPACE code nodalization. For the low steam flow rate tests, the SPACE code over-­predicts the bypass fraction irrespective of the nodalization finesse. The over-­prediction at low steam flow may be attributed to the difficulty to accurately represent the flowregime in the vicinity of the broken cold leg.

 

The Application of Knowledge Management and TRIZ for solving the Safe Shutdown Capability in Case of Fire Alarms in Nuclear Power Plants

Chia-Nan Wang, Hsin-Po Chen, Ming-Hsien Hsueh and Fong-Li Chin

The Fukushima nuclear disaster in 2011 has raised widespread concern over the safety of nuclear power plants. This study employed knowledge management in conjunction with the Teoriya Resheniya Izobreatatelskih Zadatch (TRIZ) method in the formulation of a database to facilitate the evaluation of post-fire safe shutdown capability with the aim of safeguarding nuclear facilities in the event of fire. The proposed approach is meant to bring facilities in line with US Nuclear Regulatory Commission (NRC) standards. When implemented in a case study of an Asian nuclear power plant, our method proved highly effective in the detection of 22 cables that fell short of regulatory requirements, thereby reducing 850,000 paths to 0. This study could serve as reference for industry and academia in the development of systematic approaches to the upgrading of nuclear power plants.

Corrosion Processes of Alloyed Steels in Salt Solutions

Bernhard Kienzler

A summary is given of the corrosion experiments with alloyed Cr-Ni steels in salt solutions performed at Research Centre Karlsruhe (today KIT), Institute for Nuclear Waste Disposal (INE) in the period between 1980 and 2004. Alloyed steels show significantly lower general corrosion in comparison to carbon steels. However, especially in salt brines the protective Cr oxide layers on the surfaces of these steels are disturbed and localized corrosion takes place. Data on general corrosion rates, and findings of pitting, crevice and stress corrosion cracking are presented.

Design and Development of a Radio¬ecological Domestic User Friendly Code for Calculation of Radiation Doses and Concentration due to Airborn RadionuclidesRelease During the Accidental and Normal Operation in Nuclear Installations

A. Haghighi Shad, D. Masti, M. Athari Allaf, K. Sepanloo, S.A.H. Feghhi and R. Khodadadi

A domestic user friendly dynamic radiological dose and model has been developed to estimate radiation doses and stochastic risks due to atmospheric and liquid discharges of radionuclides in the case of a nuclear reactor accident and normal operation. In addition to individual doses from different pathways for different age groups, collective doses and stochastic risks can be calculated by the developed domestic user friendly KIANA Advance Computational Computer Code and model. The current Code can be coupled to any long-range atmospheric dispersion/short term model which can calculate radionuclide concentrations in air and on the ground and in the water surfaces predetermined time intervals or measurement data.

 

Matthias Rey

Future management requires careful planning and knowledge of what options are available, how far optimizations make sense and which measures and process changes have already proven themselves elsewhere. The 2017 advanced course of the Swiss Nuclear Forum took up this topic. On the first day of the course, the focus was on solutions for optimizing system operation and maintenance. The second day focused on the employees in their changing environment. As a novelty this year, the topics of the morning input presentations were discussed in depth in workshops on both afternoons.

 

Playing Politics with Nuclear is all Part of the Game

John Shepherd

If a week is a long time in politics – a statement attributed to former British prime minister Harold Wilson – then what about a month, or several months – a period relevant for the use of nuclear power? The nuclear industry has long accepted that it can be used as a political football, to be kicked into goal or off the pitch completely depending on the situation at hand. Our industry therefore has power in the political sense too, but with power comes responsibility – nuclear leaders know that only too well and now is as good as time as ever to lead by example.

 

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