The Department of Mechanical and Nuclear Constructions of the University of Pisa has developed a computer code, HOCRA, which is able to make an initial evaluation of the capability of catalytic recombiners to remove hydrogen from the atmosphere of the safety containments of nuclear reactors in accident conditions. The code allows the analysis of the average concentration transient of hydrogen in a generic compartment of a safety containment in a nuclear reactor. The software is structured into two groups. The first, mode-1, analyzes the average concentration in all the free volume of the containment before a possible venting; whereas the second, mode-2, analyzes the average concentration transient in a containment compartment, assuming input and output flow rates into and from the compartment itself. The first part of this paper outlines the physical and mathematical model of the code, the second part reports calculations made for an advanced PWR in cooperation with ENEL.

In severe accidents, hydrogen may be generated in a nuclear power reactor and may explode damaging safety and containment systems. In a multi-compartment safety containment, phenomena due to partition walls and vents between compartments may cause a sort of 'amplification' of the maximum deflagration overpressure in single compartments; then greater pressure differences may destroy internal structures with equipment supported. Department of Mechanical and Nuclear Constructions of the University of Pisa carried out experiments with multi-compartment small scale containers about this problem. Peculiar phenomena have been identified, like 'jet ignition' oxyhydrogen torch' and 'recoil'. A new version of the experimental apparatus "LargeView" was built with a 0.3 MPa design limit pressure. A set of transducers takes the overpressure transients, while a videocamera system records the flame evolution through the glass walls of the container. Tests have been held with equipment models put inside the first and second chambers of the facility. Sensible differences in recorded maximum overpressures in tests held under the same nominal experimental conditions might be related to slight errors in the hydrogen concentration measurement, because the pressure seems to be very sensitive to the initial hydrogen concentration. These results suggest to reduce the present safety limit for the hydrogen concentration in a nuclear reactor containment.

High-temperature reactors are a potential low-carbon source of high-temperature heat for chemical plants-including hydrogen production plants and refineries. Unlike electricity, high temperature heat can only be transported limited distances; thus, the reactor and chemical plants will be close to each other. A critical issue is to understand potential safety challenges to the reactor from the associated chemical plant events to assure nuclear plant safety. The U.S. Nuclear Regulatory Commission (NRC) recently sponsored a Phenomena Identification and Ranking Table (PIRT) exercise to identify potential safety-related physical phenomena for high-temperature reactors Coupled to a hydrogen production or similar chemical plant. The ranking process determines what types of chemical plant transients and accidents could present the greatest risks to the nuclear plant and thus the priorities for safety assessments. The assessment yielded four major observations. Because the safety philosophy for most chemical plants (dilution) is different than the safety philosophy for nuclear power plants (containment), this difference must be recognized and understood when considering safety challenges to a nuclear reactor from coupled chemical plants or refineries. Accidental releases of hydrogen from a hydrogen production facility are unlikely to be a major hazard for the nuclear plant assuming some minimum separation distances. Many chemical plants under accident conditions can produce heavy ground-hugging gases such as oxygen, corrosive gases, and toxic gases that can have major off-site consequences because of the case of transport from the chemical plant to off-site locations. Oxygen presents a special concern because most proposed nuclear hydrogen processes convert water into hydrogen and oxygen; thus, oxygen is the primary byproduct. These types of potential accidents must be carefully accessed. Last, the potential consequences of the failure of the intermediate heat transport loop that moves heat from the reactor to the chemical plant must be carefully assessed.

Autonomous energy supply systems provide the possibility of producing electricity without the connection to an interconnected power grid. While modem computer programs are able to simulate such systems in detail, they usually do not take into account the time varying availability of renewable energy sources, component life and repair times. In addition, safety aspects which are important if e.g. hydrogen is involved in the system are normally not addressed. This is done in the present paper.

Testing sour gas wells safely is still a difficult problem in the world, and testing offshore gas wells with sulfureted hydrogen (H(2)S) presence requires an even higher safety level. But offshore researches published are limited, and standards, principles, regulations and manuals are scattered. Distinctive structures of well bore, well head and surface, and peculiar emergency response plan, are all need deep research. Based on the long term study on high pressure high temperature well development both on land and offshore, a brief introduction about hazards of H(2)S during well testing, and the difference between on land and offshore well testing is given firstly. Then, according to monitoring, alarming and precaution measures to H(2)S effusion in the field, typical potential engineering accidents and treating methods when testing offshore sour wells are studied. The results are helpful to establishing regulations on testing offshore sour wells.

The aim of this review is to attract hydrogen community care to the hydrogen-materials problem, that may slow down hydrogen economy entering into the mankind life. Two contrary aspects of the problem are discussed. The first is hydrogen degradation of materials, hydrogen energy equipment deteriorating, its time-life and safety. The second is hydrogen treatment of materials (HIM) permitting to create novel hydrogen technologies and advanced materials. A special attention is paid to HTM as a new, not very wide known field of Materials Science and Engineering.

The Brookhaven National Laboratory (BNL) High-Temperature Combustion Facility (HTCF) was used to perform hydrogen deflagration and detonation experiments at temperatures to 650K, Safety features that were designed to ensure safe and reliable operation of the experimental program are described. Deflagration and detonation experiments have been conducted using mixtures of hydrogen, air and steam. Detonation cell size measurements were made as a function of mixture composition and thermodynamic gas conditions. Deflagration-to-detonation transition experiments were also conducted. Results of the experimental program are presented, and implications with respect to hydrogen safety are discussed.

This report describes the progress made on the design of the cryogenic cooling system for the liquid absorber for the international Muon Ionization Cooling Experiment (MICE). The absorber consists of a 20.7-liter vessel that contains liquid hydrogen (1.48 kg at 20.3 K) or liquid helium (2.59 kg at 4.2 K). The liquid cryogen vessel is located within the warm bore of the focusing magnet for the MICE. The purpose of the magnet is to provide a low beam beta region within the absorber. For safety reasons, the vacuum vessel for the hydrogen absorber is separated from the vacuum vessel for the superconducting magnet and the vacuum that surrounds the RF cavities or the detector. The absorber thin windows separate the liquid in the absorber from the absorber vacuum. The absorber vacuum vessel also has thin windows that separate the absorber vacuum space from adjacent vacuum spaces. Because the muon beam in MICE is of low intensity, there is no beam heating in the absorber. The absorber can use a single 4 K cooler to cool either liquid helium or liquid hydrogen within the absorber.

There are analized the history and up-to-date status of cooperation in hydrogen energy community and hydrogen-materials one. The noticeable progress here is attained during the last two decades. The conclusion is made that promoting this cooperation will be a responsible task of hydrogen movement in the 21st century.