Progress for on-line acoustic emission monitoring of cracks in reactor systems

This paper reviews accomplishments and planned tasks for the NRC-sponsored research program concerned with “Acoustic Emission/Flaw Relationships for Inservice Monitoring of Nuclear Reactor Pressure Boundaries”. The objective of the acoustic emission (AE) monitoring program is to develop and validate the use of AE methods for continuous surveillance of reactor pressure boundaries to detect flaw growth. Topics discussed include testing AE monitoring on reactors, refinement of an AE signal identification relationship, study of slow crack growth rate effects on AE generation, and activity to produce an ASTM standard for AE monitoring and to gain ASME code acceptance of AE monitoring.     

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.     

Condition telemonitoring and diagnosis of power plants using web technology

The monitoring and diagnostic systems currently installed in power plants generally supply information for control room displays and for on-site personnel. Telemonitoring is also frequently used. In this case, relevant diagnostic data are transmitted remotely to a special laboratory for analysis using highly specialized equipment and software.

The appearance of the terms “Monitoring” and “Diagnosis” alongside the term “Web Technology” in the title of this paper does not mean that remote access to diagnostic systems over the Internet is being presented here as a simple extension of the existing situation.

Condition telemonitoring and diagnosis based on Web technology is a new departure in diagnostic system design philosophy. It is the technology used to integrate diagnostic systems into a customer's IT infrastructure (Intranet or Internet).

Siemens has started to use Web-based condition telemonitoring and diagnosis in some power plants (nuclear and fossil-fueled) to provide a global source of specialist support.     

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.     

Performance of advanced self-shielding models in DRAGON Version4 on analysis of a high conversion light water reactor lattice

A high conversion light water reactor lattice has been analysed using the code DRAGON Version4. This analysis was performed to test the performance of the advanced self-shielding models incorporated in DRAGON Version4. The self-shielding models are broadly classified into two groups – “equivalence in dilution” and “subgroup approach”. Under the “equivalence in dilution” approach we have analysed the generalized Stamm’ler model with and without Nordheim model and Riemann integration. These models have been analysed also using the Livolant–Jeanpierre normalization. Under the “subgroup approach”, we have analysed Statistical self-shielding model based on physical probability tables and Ribon extended self-shielding model based on mathematical probability tables. This analysis will help in understanding the performance of advanced self-shielding models for a lattice that is tight and has a large fraction of fissions happening in the resonance region. The nuclear data for the analysis was generated in-house. NJOY99.90 was used for generating libraries in DRAGLIB format for analysis using DRAGON and A Compact ENDF libraries for analysis using MCNP5. The evaluated datafiles were chosen based on the recommendations of the IAEA Co-ordinated Research Project on the WIMS Library Update Project. The reference solution for the problem was obtained using Monte Carlo code MCNP5. It was found that the Ribon extended self-shielding model based on mathematical probability tables using correlation model performed better than all other models.     

Structure and optical properties of sapphire implanted with boron at room temperature and 1000 °C

Many previous studies of ion-implanted sapphire have used gas-forming light ions or heavier metallic cations. In this study, boron (10¹⁷ cm⁻², 150 keV) was implanted in c-axis crystals at room temperature, 500 and 1000 °C as part of a continuing study of cascade density and “chemical” effects on the structure of sapphire. Rutherford backscattering-ion channeling (RBS-C) of the RT samples indicated little residual disorder in the Al-sublattice to a depth of 50–75 nm but almost random scattering at the depth of peak damage energy deposition. The transmission electron micrographs contain “black-spot” damage features. The residual disorder is much less at all depths for samples implanted at 1000 °C. The TEM photographs show a coarse “black-spot damage” microstructure. The optical absorption at 205 nm is much greater than for samples implanted with C, N, or Fe under similar conditions.     

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.     

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.     

Multi-agent-based anticipatory control for enhancing the safety and performance of Generation-IV nuclear power plants during long-term semi-autonomous operation

The use of multi-agents and anticipatory control to improve the performance and safety of nuclear power plants is discussed. The propose program seeks to advance and test via simulation a new control approach for the long-term semiautonomous and economically competitive operation of Generation-IV nuclear power plants. The approach exploits a simple but potentially powerfull idea: In order to regulate themselves in a semi-autonomous manner and be protected from potential anomalies, Generation-IV plants should act proactively, that is, effect control in anticipation of (not just in response to) potential contingencies. It is proposed to envelop the plant with two anticipatory control blankets, one pertaining to problems emerging due to wear and fatigue, and the other pertaining to unanticipated design basis events. Nuclear power plants are by their design well suited for the application of intelligent agents to carry out the safety assurance functions as they are well instrumented for purpose of defining their safety status. Each of the monitoring and control subsystems can be “agentized; i.e., legacy (existing) codes can be encapsulated in an agent “wrapper”, enabling critical information to be autonomously distributed to any agent that needs it to perform its prescribed task.     

Intermediate size pressure vessel programme (ZB 1)

One of the focal points in the discussion about the safety of nuclear power plants is the integrity of the reactor pressure vessel.In order to prove its integrity tests are in progress in an underground test facility of the main power station in Mannheim with an intermediate size vessel from the research programme “Integrity of Components”. Patches of A 533 B and modified A 508 B material were welded into the vessel ZB 1, the test temperatures are approximately 70 and 290°C. The main goal of the tests is to measure the behaviour of artificial and natural flaws during static hydrotests and simulated operational (cyclic) conditions.In the first half of the research programme the objective is to produce a crack growth of some centimetres by cyclic loading between a variable minimum pressure and a maximum pressure of about 24 MPa. The total number of load cycles will be approximately 30 000.In the second half of the tests the vessel will be loaded by a number of pressure cycles which correspond to the loading a reactor pressure vessel experiences during 40 years of operation.During the static and cyclic loading acoustic emission monitoring is being made by German and American laboratories.This paper presents details of the vessel, the test loop, results of the nondestructive examinations conducted to quantify the crack depths and results of the acoustic emission monitoring.     

Modelling of ballistic low energy ion solid interaction — conventional analytic theories versus computer simulations

The “philosophy” behind, and the “psychology” of the development from analytic theory to computer simulations in the field of atomic collisions in solids is discussed and a few examples of achievements and perspectives are given.     

The development of a diagnostic and monitoring system for vibrating pipe branches

This paper deals with a diagnostic and monitoring system for assessing the integrity of pipe branches, during the operation of the nuclear power plant. This system have been developed under the concept of “easy to use without any sophisticated analysis” and “portable”. The accuracy of the diagnosis is based on the model optimization subsystem, which automatically modifies the numerical vibration model so as to fit its natural frequency to the actual natural frequency. The information obtained by this system may be reflected to a maintenance program of the plant to assure more reliable operation of the plant.     

Ceramic matrices for plutonium disposition

One of the major issues related to the expanded use of nuclear power and the development of advanced nuclear fuel cycles is the fate of plutonium and “minor” actinides. In addition, substantial quantities of plutonium and highly enriched uranium from dismantled nuclear weapons now require disposition. There are two basic strategies for the disposition of the actinides: (1) to “burn” or transmute the actinides using nuclear reactors or accelerators; (2) to “sequester” the actinides in chemically durable, radiation-resistant materials that are suitable for geologic disposal. This paper deals with actinide-bearing materials that support the latter approach. During the past two decades, a considerable amount of research and development has been done in an effort to develop matrices for the immobilization of plutonium and the “minor actinides”, Np, Am and Cm. A variety of waste form materials – oxides, silicates and phosphates – have been developed that have a high capacity for the incorporation of actinides, are chemically durable and, in some cases, resistant to the radiation-induced transformation to the aperiodic state. These waste forms can be selected depending on the composition of the waste stream that contains the actinides, the desired materials' properties of the waste form, and the geochemical and hydrologic conditions of the specific repository. The present state-of-knowledge for these materials is such that now one can design materials for very specific conditions, such as the thermal history and accumulated radiation dose, in a repository.     

On-line monitoring of instrument channel performance in nuclear power plant using PEANO

On-Line monitoring evaluates instrument channel performance by assessing its consistency with other plant indications. Industry and EPRI experience at several plants has shown this overall approach to be very effective in identifying instrument channels that are exhibiting degrading or inconsistent performance characteristics “On-Line Monitoring of Instrument Channel Performance by EPRI (2000)”.

On-Line monitoring of instrument channels provides information about the condition of the monitored channels through accurate, more frequent monitoring of each channel's performance over time. This type of performance monitoring is a methodology that offers an alternate approach to traditional time-directed calibration. On-line monitoring of these channels can provide an assessment of instrument performance and provide a basis for determining when adjustments are necessary. Elimination or reduction of unnecessary field calibrations can reduce associated labor costs, reduce personnel radiation exposure and reduce the potential for miss-calibration.

PEANO “A Neuro-Fuzzy Model Applied to Full Range Signal Validation of PWR Nuclear Power Plant Data by Fantoni (2000)” is a system for on-line calibration monitoring developed in the years 1995–2000 at the Institutt for energiteknikk (IFE), Norway, which makes use of Artificial Intelligence techniques for its purpose. The system has been tested successfully in Europe in off-line tests with EDF (France), Tecnatom (Spain) and ENEA (Italy). PEANO is currently installed and used for on-line monitoring at the HBWR reactor in Halden. This paper describes the results of performance tests on PEANO with real data from a US PWR plant, in the framework of a co-operation among IFE, EPRI and Edan Engineering, to evaluate the potentials of PEANO for future installations in US nuclear plants.     

Material dependence of total electron emission yields following slow highly charged ion impact

The total electron emission yields following the interaction of “Slow (2 keV/a.u.) Highly Charged Ions” (SHCI) (O³⁺⁷⁺, Xe¹²⁺⁵²⁺, Au⁵⁴⁺⁶⁹⁺) with different target surfaces (highly-oriented pyrolytic graphite (HOPG), Au and SiO2) have been measured. The emission yields increase with charge state, and is found to be highest for carbon, the HOPG target, and lowest for the SiO₂ target. An empirical formula for the electron emission is including recent results from investigations of plasmon excitation following SHCI impact are used to interpret the results.     

Optimal space-energy splitting in MCNP with the DSA

The DSA theory is based on the possibility to obtain exact explicit expressions for the dependence of the second moment and calculation time on the splitting parameters. This allows the automatic optimization of the splitting parameters by “learning” the problem's bulk parameters from which the problem depended coefficients of the quality function (second moment ^* time) are constructed.

The above procedure was exploited to implement an automatic optimization of the splitting parameters in the MCNP code. This was done in a number of steps. Firstly only spatial surface splitting was considered. In this step, the major obstacle has been the truncation of an infinite series of “products” of “surface path's” leading from the source to the detector. The encouraging results of the first phase led to the inclusion of full space/energy phase space splitting.     

A mechanism for the ease of slip in UO2+x

The microstructure of plastically deformed hyperstoichiometric uranium dioxide crystals has been reexamined by transmission electron microscopy. Although the U₄O₉ phase is present with its usual superlattice structure, dislocations which thread interfaces between it and the adjacent UO₂ phase exhibit uniform contrast, (i.e., no separation into superdislocations is resolved). Dislocations lying totally within the UO₂ phase are decorated by “shadows” of gray contrast, which can be removed by heating in the microscope atmosphere. These have been identified as “atmospheres” of U₄O₉. A geometrical argument, based on the coordinates of anion interstitials published by Willis, is used to explain how these “atmospheres” might account for the observed incidence of extensive cross-slip in plastically deforming UO_2+x.     

Elevated-temperature structural design evaluation issues in LMFBR licensing

This paper describes elevated-temperature structural design issues and concerns identified by the NRC licensing review of the Clinch River Breeder Reactor Plant for a construction permit. Major issues concern weldment evaluation, notch weakening, steam generator tubesheet evaluation, and the use of “average” rather than “minimum” material properties in inelastic analysis. Other questions concern seismic effects, elastic follow-up, creep fatigue evaluation, plastic strain concentration, and transition welds. All of the issues were resolved but several required CRBRP Project commitment to perform additional confirmatory programs.     

Laser-driven pulsed emission and plasma formation of Cs3Sb photocathodes

The experimental progress of laser-driven Cs₃Sb photocathodes is reported. The cathodes prepared in an UHV system can be used to generate short-pulsed, high-brightness electron beams. Emission properties are tested under a 50–200 ns pulsed Xe⁺ laser illumination. The quantum efficiency in the range of 2–5.6% and current density of 108 A/cm² are obtained. A brightness of 1.85 × 10⁹ A/m² rad² is also measured. Mass analysis and other methods have been used for investigating the plasma formation when laser intensity rises above the “break-down” threshold. The current density increases rapidly during the plasma electron emission, but the pulse width of the emission is enlarged, and the brightness is limited. It is observed that the plasma is just composed of cesium and antimony atoms from the cathode rather than adsorbed residual gases.