WE-NET Home Page/Summary of Annual Reports 1997

3.5 Safety measures and assessment

3.5.1 R&D Goals

The research and development of an "International Clean Energy Network Using Hydrogen Conversion," known as WE-NET (World Energy NETwork), is launched in fiscal 1993. WE-NET project will construct a clean energy network on a worldwide scale, where hydrogen will be produced by employing various kinds of renewable energy such as hydropower, solar in areas blessed with these energies.

(1) Identification of Guidelines for System Safety Design

In phase I (1993 to 1998), we will conduct a survey on safety ideas, safety goals, safety design guidelines and accidents in domestic and foreign energy systems, as well as on laws and regulations, specifications and standards, which are applicable to hydrogen energy systems.

For each component of the WE-NET system, we will identify postulated anomaly/accident scenarios, and estimate their effects on humans and structures with the objective of specifying the safety requirements required for each component of the system as well as a basic scheme to ensure system safety. In fiscal year 1997, based on the information of the design for each WE-NET system, survey of postulated abnormal incident and accident scenarios will be conducted. We will continue to conduct survey of a set of safety requirement for each of the system considered.

(2) Pre-arrangements for Analyses on Various Accident and Safety

In phase I (1993 to 1998), information to be used in making various accident and safety analyses for each WE-NET system component will be obtained. Simulation programs in public domain will be studied. And proprietary simulation models for application to typical accident cases will be developed. A future research plan for assessment methodology will be identified and reflected in the safety design scheme. In fiscal year 1997, information required for safety analyses and assessments will be collected. We will continue to develop some simulation models that postulate the dispersion, explosion and ignition of the hydrogen. Further, we will make a full-scale investigation of the integration of the models.

(3) Others

Exchange of safety-related information with associated subtask groups from the planning stage of experiment facilities or medium-sized plants will be continued as in the fiscal year 1996 in order to ensure safety measures and assessments for some part or the full part of the WE-NET system. Further, the second mini-workshop on hydrogen safety will be held. Then attendants from overseas and Japan will have a chance to exchange opinions and have discussions on safety topics, and introduce the progress in each country.

3.5.2 Results in fiscal year 1997

(1) Compilation of Guidelines Database for System Safety Design

Information of safety or accident regarding liquid hydrogen and LNG was continuously collected from the existing chemical plants. Survey of safety technologies for hydrogen at high temperature and high pressure has begun. Those shall be useful in making a definite plan for safety design of the WE-NET system. The contents are as follows:

Investigation of instruction manuals for liquid hydrogen available from National Aeronautics and Space Administration (NASA, USA) or National Space Development Agency of Japan(NASDA) was conducted. Referring to safety design concepts of the chemical plants, preparatory work for making safety design guidelines for the WE-NET system has begun.
Based on the progress made by that time and the information about the design of the related systems developing at each subtask groups, investigation was conducted to make specific safety requirements for each WE-NET system.

(2) Modification and Evaluation of Models for Safety Analyses

We have tried to modify both the simulation model for hydrogen dispersion and that for hydrogen explosion or fire. In addition, we have almost completed identification of problems prior to integration of the simulation programs. Actual contents are as follows:

An experiment plan applicable to a small-scale experiment was made to estimate the behavior of evaporation of liquid hydrogen in a fluid state. Further, we have modified the evaporation model included in the CHAMPAGNE code. On the model of hydrogen evaporation dispersion and flow in the atmosphere, we have made research of a turbulent mixing effect. We have summarized tasks for fiscal 1998.
On the SRI code included in AACA which postulates explosion and fire of a compressed hydrogen tank, incorporation of new functions into the program was made to estimate a blast wave, fire and fragment hazard to humans and peripheral structures. In addition, we have preliminarily added a new function to the AACA in order to assess a damage value based on actual cost data, depending upon the conditions of the peripheral structures, such as layout and quality of materials used, etc.
Preliminary research of the interface necessary to link the two codes mentioned above has been conducted. There is much prospect that preliminary pre-integration is possible in fiscal 1998.

(3) Others

The second mini-workshop on hydrogen safety was held in Menlopark, CA, USA. After considerable discussion with experts from USA, Germany and France, we reached an agreement that it needs an actual test data to give grounds for safety standard.
Exchanging safety-related information with associated subtask groups was made. (the test facilities for evaluation of hydrogen combustor; subtask-8, the facilities for materials evaluation in liquid hydrogen; subtask-6, the facilities for insulation performance test in liquid hydrogen; subtask-5). As a result, each subtask groups has decided to adopt practicable measures appropriately.

3.5.3 Research Plan for fiscal year 1998

(1) Identification of Guidelines for System Safety Design

Safety requirements for each WE-NET system and a basic scheme to ensure system safety will be specified for each WE-NET system. Based on them, we will prepare a safety design plan. Actual plans are as follows:

Investigation of safety concepts for LNG facilities, which are considered to be similar to those for hydrogen facilities, will be conducted. Study of safety target in handling hydrogen at high temperature and high pressure will be also conducted. Safety-related information thus collected will be summarized. Further, investigation of domestic and foreign standards will be conducted to make the safety design plan (draft) applicable to the WE-NET system.
Based on the findings obtained from the previous studies, abnormal incident and accident in individual WE-NET systems will be extracted for identification of safety requirements. All these works will be reflected in the compilation of the safety design plan.

(2) Pre-arrangements for Analyses on Various Accident and Safety

By using hydrogen dispersion simulation code and explosion and fire simulation code, we will estimate the hazard of liquid hydrogen spillage from a storage tank. Further, we will identify a research program for assessment methodology and include it in the safety design plan. Actual plans are as follows:

Investigation of experimental data on liquid hydrogen evaporation factors will be conducted. Survey of technologies for validating the evaporation model and the dispersion model included in CHAMPAGNE code will be made. For validation, a definite experiment plan will be prepared. Assessment of the dispersion and flow model in the atmosphere, especially, a turbulent mixing effect, will be conducted by using modified model. Based on the outcome, tasks will be summarized.
On the explosion and fire model for a compressed hydrogen tank, we plan to expand a modeling library of the accident analysis computer algorithm (AACA) to assess the impact of blast wave, radiation, flying objects and loss. Survey of improvements will be started to summarize necessary tasks.
Linking the two simulation models mentioned above will be made to estimate the effect of liquid hydrogen spillage and explosion in a two-dimensional way and identify several problems to be solved in future. A specific research plan for assessment methodology will be made.

(3) Investigation of Safety Technologies for Dispersed Use of Hydrogen

Investigation of safety technologies for dispersed use of hydrogen, including a small scale production, transportation and storage as typified by hydrogen vehicles and hydrogen refueling station planning in the Phase II of the WE-NET project, will be conducted together with the related subtask groups.