PSB-VVER simulation of Kozloduy NPP “loss of feed water transient”

This paper provides a comparison between the PSB test facility experimental results obtained during the simulation of loss of feed water transient (LOFW) and the calculation results received by INRNE computer model of the same test facility. Integral thermal-hydraulic PSB-VVER test facility located at Electrogorsk Research and Engineering Center on NPPs Safety (EREC) was put in operation in 1998. The structure of the test facility allows experimental studies under steady state, transient and accident conditions.RELAP5/MOD3.2 computer code has been used to simulate the loss of feed water transient in a PSB-VVER model. This model was developed at the Institute for Nuclear Research and Nuclear Energy for simulation of loss of feed water transient.The objective of the experiment “loss of feed water”, which has been performed at PSB-VVER test facility is simulation of Kozloduy NPP LOFW transient. One of the main requirements to the experiment scenario has been to reproduce all main events and phenomena that occurred in Kozloduy NPP during the LOFW transient. Analyzing the PSB-VVER test with a RELAP5/MOD3.2 computer code as a standard problem allows investigating the phenomena included in the VVER code validation matrix as “integral system effects” and ”natural circulation“. For assessment of the RELAP5 capability to predict the “Integral system effect” phenomenon the following RELAP5 quantities are compared with external trends: the primary pressure and the hot and cold leg temperatures. In order to assess the RELAP5 capability to predict the “Natural circulation” phenomenon the hot and cold leg temperatures behavior have been investigated.This report was possible through the participation of leading specialists from Kozloduy NPP and with the support of Argonne National Laboratory (ANL), under the International Nuclear Safety Program (INSP) of the United States Department of Energy.     

Progress in “COE-INES”

In the year 2002 and 2003, the Japanese Ministry of Education, Culture, Sports, Science and Technology started the “ The 21st Century Center of Excellence (COE) Program”, which is planned to continue for 5 years. A program proposed by Tokyo Institute of Technology “Innovative Nuclear Energy Systems for Sustainable Development of the World” simply called as COE-INES was selected as only one program in nuclear engineering field. The program consists of four main activities: research, education, society and internationalism. The research will be performed on the innovative nuclear energy systems, which include innovative nuclear reactors and innovative fuel cycles. Both free thinking and overall vision are taken on the research, and stressed on education also. In the education, COE-INES Captainship Program is promoted by integrating research with education, and we will foster creative researchers and engineers. Society is also a very important issue for nuclear energy. We try to coevolve nuclear energy with society and to strive towards the fulfillment of SR as well as to research innovative nuclear energy systems. We believe these ideas are occupied by many scientists in various countries. Then we are promoting the international collaboration for research and education on innovative nuclear energy systems.     

Irreversible energy losses of flow through porous and perforated plates

For a realistic numerical simulation of a hypothetical core disruptive accident (HCDA) it is often important to take into account perforated plates. Inclusion of the plates drastically changes the loading pattern of the containment and a significant amount of the fluid's energy is dissipated as it passes through the plates. At present the PISCES-2DELK program simulates the perforated plates explicitly by defining the geometric boundary and the fluid passages. This boundary is attached to a movable structure, thereby ensuring the correct fluid-structure interaction. Equally important as the correct fluid-structure interaction is the energy dissipation, associated with fluid flow through the narrow passages. This aspect will be treated in this paper. Simple PISCES-2DELK calculations will illustrate that the fluid undergoes an internal energy rise, well beyond the reversible component (de = −pdv). The excess energy can be marked as heating of the fluid and is therefore irreversible. Furthermore, as the flow through the narrow passages tends to a “stationary state”, an a posteriori computed energy loss factor C_D levels off to a value which corresponds to those common in the literature. The method of explicitly defining the geometric boundaries of perforated/porous structures is advantageous, for the following reasons: (a) it takes into account volume occupying effects of the perforated/porous plates; (b) it is equally applicable for the dynamic and for the more or less stationary state; and (c) it simulates the fluid-structure interaction and energy dissipation of the fluid, without any a priori assumptions about energy loss factors.     

Addendum to “an evaluation of alternative nuclear strategies”

This paper presents an assessment by Battelle-Columbus of the technology associated with several reactor concepts which may be considered “advanced” beyond existing LWR's in terms of improved natural resource utilization. The concepts chosen for evaluation and intercomparison are the HTGR, GCFR, MSBR and LWBR. Numerous conclusions may be reached from the study and some interesting trends can be observed. Of greatest significance is the fact that the strategies associated with alternative reactors/fuel cycles will not produce dramatic decreases in short-term fissile demand. A second major conclusion is that all of these advanced systems are considered capable of meeting applicable environmental requirements. A third conclusion is that there is no apparent technical reason for deletion of development efforts on any of these reactors, providing that a commercial interest, complete with significant commitment, is existent.     

Conceptual design of multi-purpose heat reactor “Nuclear Heat Generator”

Small heat reactors can apply to on site demand such as district heat and air conditioning, industrial process heat, greenhouse, and seawater desalination in urban and rural areas. The purpose of this paper is to design conceptually a multi-purpose reactor named “Nuclear Heat Generator (NHG)” which could be installed in energy consuming area. The reactor of 1MWt output is designed without any needs for fuel exchange and decommissioning on site. This cassette typed reactor vessel with sealing is transported to specified fuel fabrication shop every 3 to 4 years in order to exchange used fuels. Steam generators are involved in the self-pressurized integrated reactor with natural circulation. Generated steam pressure from heating reactor is 0.88 MPa (saturated) which is so less than that of current water reactors. Under low steam pressure it is considerably easy to make design of containment vessel and safety device. For economic competition overcoming scale demerit it will be necessary for the cassette type reactor to optimize its system design for the multi-production effect as well as modular construction and recycling system.     

The new code “RCC-MR” — Rules for design and construction of LMFBR components

In 1978, Commissariat à l'Energie Atomique, Electricité de France, and Novatome decided to undertake a common effort to gather a complete collection of rules to apply for design of LMFBR components. The first issue of this work is now being published by AFCEN as the “RCCM” code. The preparation of the design rules used largely the experience gained in Superphenix components analysis, and the results of the large R&D program performed as a support for the design of this plant or at longer term perspective, coordinated by a scientific advisary council of AFCEN (Association Française pour les règles de Conception et de Construction des matériels des Chaudières Electronucléaires).     

On the Lambropoulos-Luco's δ-“no go” conjecture in variational flux synthesis

The Lambropoulos-Luco's δ-“no go” conjecture and related controversies in the domain of the variational flux synthesis with discontinuous trial functions are completely resolved in terms of the functionals, ^(±)δ⁽ⁿ⁾(x − x_o), in the frame of the new spaces of functionals, which are topological dual spaces of discontinuous complex valued functions spaces occurring with left and right continuities.     

Low-energy unstable nuclear beam channel “SLOW” at the RIKEN ring cyclotron

A new type of low-energy radioactive nuclear beam channel “SLOW” has been constructed at the RIKEN ring cyclotron facility, intended not only for the study of emission mechanisms of various low-energy radioactive as well as stable isotope ions from a characterized surface of the primary target, but also for the generation of useful radioactive ion beams for surface-physics studies of the secondary target.

In the commissioning experiment of the SLOW beam channel, the reaction products of a heavy-ion induced nuclear reaction have been observed after surface ionization at a hot tungsten target.     

Attachment concept for the “multi module segments” in a pulsed DEMO reactor

The pulsed thermonuclear demonstration reactor (DEMO) features challenging operational conditions such as high neutron fluxes, high temperatures, and significant thermo-mechanical stresses. These conditions do not require only a selection of advanced structural materials, but also the development of reliable means to assemble the in-vessel components together; allowing thermal expansions, disassembly, and maintenance in attractive scenarios. Over the course of DEMO lifetime, the materials are subjected to embrittlement by neutron irradiation, swelling, considerable thermo-mechanical fatigue and creep. Traditional joining methods may be rarely used in the harsh fusion environment to assemble different components. In addition any proposed layout should cope with the limited space available inside the vacuum vessel (VV).The objective of this study is to review the proposed attachment systems (developed within the latest European DEMO Conceptual Study) for the vertical segmentation concept called “multi module segments” (MMS). In order to find some place to house the attachments the blanket is cut respecting the Tritium Breeding Ratio limit for tritium self sufficiency. The conditions, neutronic and thermal, in which the attachments are supposed to operate, are calculated. The effects of pulsed operations have also been taken into account. The design of the attachments with the available structural materials with and without an active cooling system is analysed and a new concept for plug/unplug attachments is also suggested.     

The 21 century coe program: COE-INES “innovative nuclear energy systems for sustainable development of the world”

In the year 2002 and 2003 the Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT) started the “Priority Assistance for the Formation of Worldwide Renowned Centers of Research — The 21st Century Center of Excellence (COE) Program”, which is planned to continue for 5 years.

A program proposed by Tokyo Institute of Technology “Innovative Nuclear Energy Systems for Sustainable Development of the World” simply called as COE-INES was selected as only one program in nuclear engineering field.

The program consists of research, education and international collaboration. The research will be performed on the innovative nuclear energy systems, which include innovative nuclear reactors and innovative fuel cycles. The research on innovative nuclear reactors does not cover only reactor design studies but also its utilization systems such as hydrogen production. Both free thinking and overall vision are taken on the research. They are stressed on education also.

In the education program (COE-INES Captainship Program) by integrating research with education, we will foster creative researchers and engineers. The program also provides lectures at the professional engineer level, and also various opportunities to cultivate internationalism.

We believe these ideas are occupied by many scientists in various countries. Then we have a plan to promote the international collaboration for research and education on innovative nuclear energy systems.     

Main R&D issues for fast reactor structural design standard

For realization of economical and reliable fast reactor (FR) plants, the Japan Atomic Energy Agency (JAEA) and the Japan Atomic Power Company (JAPC) are cooperating on the “Feasibility Study on Commercialized FR Cycle Systems”. To certify the design concepts through evaluation of the structural integrity of FR plants, the research and development of the “Elevated Temperature Structural Design Guide for Commercialized Fast Reactor (FDS)” is recognized as an essential theme. The FDS focuses on particular failure modes of FRs such as ratchet deformation and creep-fatigue damage due to cyclic thermal loads. For precise evaluation of these modes, the research and development for three main issues is in progress. First, the “Refinement of Failure Criteria” needs to be addressed for particular failure modes of FRs. Secondly, the development of “Guidelines for Inelastic Design Analysis” is conducted to predict elastic plastic and creep deformation under elevated temperature conditions. Lastly, efforts are being made toward preparing “Guidelines for Thermal Load Modeling” for the design of FR components where thermal loads are dominant.     

The use of energy absorbers to protect structures against impact loading

When a flying missible impacts a fixed structure, the interface loading is dependent on the deformation characteristics of both impacting and impacted bodies. If both are too rigid to accommodate the amount of gross deformation required to neutralize the incoming kinetic energy, or if such energy absorption has a chance to proceed in uncontrolled and unreliable ways, then there is a need to interpose a specifically designed “energy absorber” between missile and structure, from which a well-defined load time history can be derived during the course of impact.

The required characteristics of such an energy absorption material are:

• the capability to accommodate large permanent deformation without structural failure; and

• the reliable and controlled “load-deformation” (or “stress-strain”) behaviour under dynamic conditions, with an aim at an optimal square shape curve.

Consideration must also be given to environmental or other disturbing effects, like temperature, humidity, and “out of plane” loading. A short survey is presented of the wide range of energy absorbers already described in technical papers or used in a number of practical safety applications within varied engineering fields (from vehicle crash barriers to high energy pipe whipping restraints). However, with such open a literature, information is usually lacking in the specific data required for design analysis.

The following “energy absorption” materials and processes have thus been further experimentally investigated, with an a aim at pipe whipping restraint application for nuclear power plants:

1. (1) plastic extension of austenitic stainless steel rods;

2. (2) plastic compression of copper bumpers; and

3. (3) punching of lightweight concrete structures.

Dynamic “stress-strain” characteristics have been established for stainless steel bars at several temperatures under representative loading conditions. For this purpose, a test rig has been specifically designed to incorporate a number of adjustable parameters and to behave as a representative “slice” of an actual pipe whipping restraint; typical strain rates are in the 10 sec⁻¹ range. The behaviour of copper bumpers has been compared under static and dynamic conditions (using a conventional drop weight test (DWT) machine); as no significant strain rate effects were emphasized, only static tests have been further developed. The DWT rig was used again to investigate crushing or punching of cellular concrete under varying geometries and loading conditions. To remedy certain deficiencies of the regular commercial grades of cellular concrete, special lightweight mixtures have been studied to optimize material toughness and provide a wider range of specific resistance.Results of this experimental program are presented and discussed. The use of energy absorbers is then illustrated for a few typical pipe whipping restraints. The design of restraints is based on real dynamic characteristics of “energy absorption” material as produced by the test program. To derive design loads of restraints, a number of methods can be used ranging from a simplified “energy balance” graph to sophisticated plastodynamic computer analysis. Typical results are presented and discussed to compare the efficiency of these alternative methods.     

Hybrid soliton nuclear reactors: A model and simulation (encapsulated long living accelerator driven system)

We intend to explore the potential of Hybrid Soliton Reactors (Réacteur Hybride à Soliton, RHYS) for producing energy. In our case an encapsulated long living fission reactor is driven by a proton accelerator, who produces neutrons on a target. In a first part we give the mathematical approach of such a sub-critical reactor, as an extension of the “Soliton Reactor” which was recently proposed by different authors, Edward Teller, L.P. Feoktistov, and others (H. Sekimoto under the name “Candle reactor”). In a second part we give results of simulations and explore the possibilities to control such a system.     

Core concept of a passive-safety fast reactor “METAL-KAMADO” and reactivity coefficients

New concept of a passive-safety simple fast reactor “METAL-KAMADO” with metallic fuels is presented, which has same concept as a passive-safety thermal reactor “KAMADO”. A fuel element of the “METAL-KAMADO” consists of metallic fuel (U–10%Zr) and cooling holes of He gas flow. These fuel elements are located in a reactor water pool of atmospheric pressure (0.1 MPa) and low temperature (<60 °C). In case of LOF, decay heats of fuel elements are removed by natural heat transfer from surfaces of the fuel elements to the reactor water pool.

Preliminary neutronic calculations of the “METAL-KAMADO” show possibility of high burn-up of more than 120 GWd/t with 10% enriched U–Zr fuel. Reactivity coefficients of the core are also discussed.     

Modern applications of high energy ion beams: from “single-event burnout” to human eye cancer treatment

Energetic ion beams, originally the domain of nuclear physics, become increasingly important tools in many other fields of research and development. The choice of ion species and ion energy allows an enormously wide variation of the penetration depth and of the amount of the electronic stopping power. These features are utilized to modify or damage materials and living tissues in a specific way. Materials modification with energetic ion beams is one of the central aims of research and development at the ion beam laboratory, ISL-Berlin, a center for ion-beam applications at the Hahn-Meitner-Institut Berlin. In particular, energetic protons will be used for eye cancer treatment. Selected topics such as the “single-event burnout” of high power diodes and the eye cancer therapy setup will be presented in detail.     

Some conclusions with regard to the safety assessment of cracked components drawn from the research programme “integrity of components” (FKS II) atthe present state

The continuation of the research program “Integrity of Components”, Phase II, mainly deals with further evaluation and assessment of material properties and the application of data from small standard specimens to large scale specimens and components. This includes the use of advanced numerical methods to check the transferability of fracture mechanics parameters with regard to the type of load and degree of multiaxiality on the failure behaviour of fracture mechanics specimens with component-like dimensions. Further points of interest are the relationship between upper shelf toughness and load-bearing capacity, the influence of neutron irradiation on the properties, and the effect of corrosion on cyclic crack growth.     

Shape coexistence effects of super- and hyperdeformed configurations in rotating nuclei with 58 ≤ Z ≤ 74

Total energies are calculated for 138 even-even nuclei with proton numbers Z = 58 – 74 and for spins varying between I = 0 (ground states) and the maximum value corresponding to the fission limit induced by rotation. Calculations are based on the Strutinsky method and the cranking approximation. The results are presented in the form of two-dimensional maps of the total nuclear energy as a function of the quadrupole deformations, β₂ and γ, and spin. At each spin value and at each (β₂, γ) point the energies are minimized with respect to the hexadecapole deformation, β₄. The macroscopic energy term in the Strutinsky formula corresponds to the “folded-Yukawa plus exponential” formulation proposed by Møller and Nix. The microscopic energy term was calculated using the universal Woods-Saxon approach. Both terms were tested to ascertain that they reproduce the observed high-spin behavior of nuclei in the mass range considered.     

Beam heating and cooling of thick targets for on-line production of exotic nuclei

Calculations have been made of energy deposition distributions for “thick” targets (1 mole/cm²) employed in on-line production of exotic nuclei using the Monte Carlo based LAHET code system for high-energy charged particle transport. A variety of target materials and incident proton beam energies have been examined. For 600 MeV protons, the results are compared to those from a similar study reported in the literature. The agreement between the two studies for total energy deposition is reasonably good for monatomic targets, but the results differ in some details of the energy deposition distributions. Target cooling, both radiative and conductive, is examined to assess the suitability of existing target concepts exposed to bombardment by intense (up to 100 μA), energetic (500 MeV to 1.2 GeV) proton beams to produce exotic nuclei. Implications of cooling requirements to target material selection and design are discussed.     

Numeric̀al modelling of ultrasonic scattering by cracks

Two basic aspects of numerical modelling of ultrasonic wave scattering by cracks in solids are discussed in the present paper: how do several standard mathematical procedures to obtain numerical values for scattered fields compare with respect to validity and accuracy, and what conclusions can be drawn from the spatial and temporal structure of these fields for identification and imaging purposes. For simplicity, the model of a plane twodimensional strip-like scatterer with stress-free boundary condition embedded in a linear, homogeneous and isotropic solid has been chosen, and scattering amplitudes for P → P, P → SV, SV → SV, SV → P wave fields are compared with respect to the methods of eigenfunction expansions (EIFU), numerical solution of integral equations (INT), elastodynamic physical optics (EPO) and elastodynamic geometric theory of diffraction (GTD). The first two methods are supposed to yield “exact” numerical results, whereas EPO and GTD rely on physical assumptions to yield simplified approximate but analytical expressions whose range of validity could then be investigated by comparison with the “exact” results giving rise to an estimation of their applicability.The integral equation method is then utilized to yield scattered fields in the time domain for pulsed excitation. Comparison with easily interpretative GTD-results exhibits specific features of these transients in terms of wavefronts and resonances, which form the basis of appropriate imaging and identification algorithms. Preliminary fundamental experiments support the underlying theory.