Design of an electron microscope phase plate using a focused continuous-wave laser

We propose a Zernike phase contrast electron microscope that uses an intense laser focus to convert a phase image into a visible image. We present the relativistic quantum theory of the phase shift caused by the laser-electron-interaction, study resonant cavities for enhancing the laser intensity, and discuss applications in biology, soft materials science, and atomic and molecular physics.Comment: 5 pages, 3 figure

Conjugating ALARA, BEPU, Safety Margins and Independent Assessment in Nuclear Reactor Safety

ALARA (As-Low-As-Reasonably-Achievable) is an early principle in Nuclear Reactor Safety, NRS (Nuclear Reactor Safety): Designers and Operators must do their best to minimize doses to the humans. BEPU (Best Estimate Plus Uncertainty) is an approach in Accident Analysis, part of NRS: one may state that BEPU implies the best use of computational tools to determine the safety of nuclear installations. Then, ALARA may be seen at the origin of BEPU, or ALARA is at the origin of BEPU. Furthermore, BEPU (and BEPU elements like V & V, Scaling, procedures of code application and code coupling, etc.) can be extended to all analytical parts of the Final Safety Analysis Report (FSAR). This brings to BEPU-FSAR. Safety Margin (SM) is an established concept in NRS: a few dozen SM values must be calculated in current safety analyses and demonstrated to be acceptable. The SM concept can be extended to everything part of the design, the operation and the environment for a Nuclear Power Plant (NPP) Unit. Here the environment includes the personnel in charge of activities connected with the NPP. The Extended SM concept, E-SM, implies the formulation of some ten-thousands SM values, which shall correspond to a similar number of monitored variables. Reasons for E-SM are the examples in section 4.1. Independent Assessment (IA) is an early requirement in NRS: data ownership and system complexity prevented so far a comprehensive application of the requirement. IA analyses conflict with industry policies to keep proprietary data. IA based BEPU-FSAR analyses are essential to finalize the E-SM design. In the paper we discuss that: a) ALARA is at the origin of BEPU; b) BEPU-FSAR analyses are the natural origin of E-SM values; c) The implementation of E-SM equals to introducing an additional physical barrier against the release of fission products

NEW SAFETY BARRIER FOR CURRENT AND FUTURE NUCLEAR REACTORS

A proposal is formulated in the present paper to improve the safety of existing and future nuclear reactors. The proposal is based upon the introduction of new safety barrier against the release of radioactivity generated by the fission chain process. Basically, two motivations for the proposal arise: a) in the last two or three decades experimental evidence demonstrated that the established barrier constituted by the fuel pin clad is weak and easily trespassed by fission products during various phases of the fuel cycle, with main regard (here) to the in-core irradiation; b) the probability of core melt must (and can) be substantially lowered by adopting outcomes from recent researches with main reference to the reached capabilities of computational tools. Furthermore, the correct interpretation of the words ‘feedback from lessons learned’ impose that the conditions which led to the occurred severe accidents are understood to be not replicable in the future and, according to the statement of Australian and Chinese scientists, “upgrading and strengthening a nuclear regulatory system is not optional but imperative to prevent the next core meltdown”. The proposal aims at fixing bases for possible strengthening of current Nuclear Reactor Safety by combining the logical frameworks connected with the terms As-Low-As-Reasonably- Achievable (ALARA), Best-Estimate-Plus-Uncertainty (BEPU), Extended-Safety-Margin (ESM) and Independent-Assessment (IA). The cost for the implementation of the proposal is expected to be affordable from a financial viewpoint and to contribute to restoring the public confidence towards nuclear technology

Improving Safety: Current and Future Nuclear Reactors

THE ELEMENTS FOR THE PROPOSAL ALARA (As-Low-As-Reasonably-Achievable) is an early principle, adopted for Radioprotection & disconnected from DSA. IA (Independent Assessment) is a requirement, pursued only in principle: a wish rather than an achievement . BEPU (Best Estimate Plus Uncertainty) is a key approach [origin of the term: nuclear thermal-hydraulics and AA during the ‘90s], not commonly accepted. E-SM (Extended Safety Margin) is derived from SM, i.e. an established concept in nuclear reactor safety ERT (Emergency Rescue Team) is a virtual entity: it shall be mandatory after Fukushima

ADDING A SAFETY BARRIER FOR EXISTING AND NEW NUCLEAR POWER PLANTS

A proposal is formulated in the present paper to improve the safety of existing and future nuclear reactors. The proposal is based upon the introduction of a new safety barrier against the release of radioactivity generated by the fission chain process. Basically, two motivations for the proposal arise: a) in the last two or three decades experimental evidence demonstrated that the established barrier constituted by the fuel pin clad is weak and easily trespassed by fission products during various phases of the fuel cycle, with main regard (here) to the in-core irradiation; b) the probability of core melt must (and can) be substantially lowered by adopting outcomes from recent researches with main reference to the reached capabilities of computational tools. Furthermore, the correct interpretation of the words ‘feedback from lessons learned’ impose that the conditions which led to the occurred severe accidents are understood to be not replicable in the future and, according to the statement of Australian and Chinese scientists, “upgrading and strengthening a nuclear regulatory system is not optional but imperative to prevent the next core meltdown”. The proposal aims at fixing bases for possible strengthening of current Nuclear Reactor Safety by combining the logical frameworks connected with the terms As-Low-As-Reasonably- Achievable (ALARA), Best-Estimate-Plus-Uncertainty (BEPU), Extended-Safety-Margin (E-SM), Independent-Assessment (IA) and Emergency-Rescue-Team (ERT). The cost for the implementation of the additional barrier is expected to be affordable from a financial viewpoint and to contribute to restoring the public confidence towards nuclear technology

[116] THERMAL-HYDRAULIC PHENOMENA

FOREWORD & SCOPE ISSUED PAPER J NED 2018 ORIGINATING DOCS/ BRIEF HISTORY 116 PHENOMENA (TH-P) LIST CROSS-LINKING Reactor Types, TH-P, Accident Scenarios and Parameters CONCLUSIONS & PROPOSED DEVELOPMENTS ACKNOWLEDGEMENT

BEPU and Safety Margins in Nuclear Reactor Safety

Abstract. Approaches like Best Estimate Plus Uncertainty (BEPU) and concepts like Safety Margins (SM) are well established in Nuclear Reactor Safety (NRS). However continuous improvements in analytical techniques and in the sophistication of hardware products do not necessarily correspond to new industrial applications within Nuclear Power Plants (NPP) technology. The declining condition for nuclear technology also contributes to the lag between developments and applications definitely causing NPP safety at a level below the achievable level. The possibility to extend BEPU to all areas of the Final Safety Analysis Report (FSAR), so-called BEPUFSAR is outlined in the paper. This should be combined with the Extension of the SM concept (E-SM). BEPUFSAR techniques may be at the origin of E-SM which also will need specific monitoring hardware. All of this may open new horizons for NRS and for acceptance of NPP by the public and the decisions makers. The paper describes recent accomplishments in the areas of BEPU and E-SM

The need of adding a safety barrier to water cooled nuclear reactors

The present paper deals with the proposal of an additional safety barrier for the class of large (1000 MWe or more) Light Water Reactors (LWR) now in operation, in construction, or under design. Emphasis is given to the motivations or the needs for the barrier. Two main parts of the paper can be distinguished. The following topics are discussed in the former part: (a) the weakness of the barrier constituted by the current design of nuclear fuel; (b) the continuously increasing complexity of the system, with main reference to the Instrumentation and Control (I&C); (c) the role that the Large Break Loss of Coolant Accident (LBLOCA) had for arriving at the current layout of the Reactor Coolant System (RCS). Furthermore avoiding the severe accidents in 1979, 1987 and 2011, is at the basis of the proposal. In the latter part, the elements of the proposed technological safety barrier are discussed: the As-Low-As-Reasonably-Achievable (ALARA) principle, the Best Estimate Plus Uncertainty (BEPU) approach, the Extended Safety Margin Detection (E-SMD) hardware, the Emergency Rescue Team (ERT) strategy (or a virtual entity for the reactor) and the Independent Assessment (IA) concept. The additional safety barrier, although not demonstrated in the paper, is expected to reduce for a factor in the range 10-1000 the probability of core melt and to have a cost in the order of 1% the cost of a nuclear reactor unit

Introduction of an additional safety barrier for nuclear power reactors

In the present paper a proposal is formulated to improve the safety of existing and future nuclear reactors. The idea is based upon the introduction of a new safety barrier against the release of radioactivity generated by the fission chain process. The proposal aims at fixing bases for possible strengthening of current Nuclear Reactor Safety by combining the logical frameworks associated with the concepts As-Low-As-Reasonably-Achievable (ALARA), Best-Estimate-Plus-Uncertainty (BEPU),Extended-Safety-Margin (E-SM), Independent-Assessment (IA) and Emergency-Rescue-Team (ERT). The expected impact of the new barrier upon selected nuclear accidents is outlined. The cost for the implementation of the additional barrier is expected to be affordable from a financial viewpoint and to contribute to restoring the public confidence towards nuclear technology