Tadaaki Ishikawa

Development of Inherently Safe Technologies for Large Scale BWRs: (5) Operation Support System for Plant Accidents

When accident events are caused by a large-scale natural disaster, conditions beyond those at the plant site may affect the accident. As well, quick diagnosis and recognition of damaged equipment are necessary. We have been developing inherently safe technologies for boiling water reactor (BWR) plants in response to these. An operation support system for plant accident events is one of these technologies. Our operation support system identifies accident events and predicts the progression of plant behavior.The system consists of three main functions: sensor integrity diagnosis, accident event identification, and plant simulation functions.The sensor integrity diagnosis function diagnoses whether sensor signals have maintained their integrity by correlating redundant sensors with the plant design information.The accident event identification function extracts a few of candidate accident events using alarm and normal sensor signals received by the sensor integrity diagnosis function. The scale and position of the accident event are determined by comparing plant simulation results with normal sensor signals.The plant simulation function uses a detailed three-dimensional model of the nuclear reactor and plant. This simulation can predict future plant behavior on the basis of identified accident events.This proposed operation support system provides available results of accident event identification and plant condition prediction to plant operators. This system will reduce the occurrence of false identifications of accident events and human errors of operators.Copyright

New Four-stroke Diesel Engine Oil Standards for Japanese Market: JASO DH-2 and DL-1

This paper reviews the development of the new four-stroke diesel engine oil standards, JASO DH-2 and DL-1 (JASO M335-05) for Japanese automotive diesel engines equipped with after treatment devices, e.g. Diesel Particulate Filter (DPF) to meet the new long-term emissions regulations. These standards have been introduced in Japan in April 2005. The standards prescribe the minimum performance for engine oils conforming to Japan-made four-stroke diesel engines with aftertreatment devices using low sulfur diesel fuel (less than or equal to 0.005 mass % sulfur). The engine test requirements for these new standards are basically the same as those of the JASO DH-1 automotive diesel engine oil standard (JASO M-355 2000) to meet engine oil performances with soot dispersancy (ASTM D 5967-99), piston detergency (JASO M336-98), thermal and oxidation stability (ASTM Seq. IIIE and IIIF), and anti-wear performance (JASO M354-99). The specified bench tests measure hot surface deposit control, anti-foaming, volatility, anticorrosion, shear-stability, base number, and seal compatibility. Limits for chemical elements and sulfated ash are newly set to protect aftertreatment devices.

Fabrication of an optical beam scanning array integrating mirror and lens arrays by passive self-alignment using precisely formed through-holes

An optical beam scanning array (OBSA) integrating two mirror arrays and a collimator-lens array was fabricated. The passive self-alignment inserting a pin into a through-hole was carried out for integration of the mirror arrays and the collimator-lens array. The mirror arrays consist of a mirror substrate with 35 single-axis-rotational mirrors and an electrode substrate for actuating the corresponding mirror by electrostatic force. Each substrate includes two kinds of through-holes: one for passing a collimated-optical beam through, the other for inserting a pin. The conditions for deep-reactive-ion etching (DRIE) of silicon were optimized to form through-holes suitable for passive self-alignment. DRIE from both surfaces of a silicon wafer under the optimized DRIE conditions—a C4F8/SF6 gas-flow ratio of 90% and a bias power in SF6 gas of 110 W—formed precision through-holes with an average undercut of 3.4 µm and an average sidewall angle of 89.9°. The passive self-alignment then yielded an assembly deviation of less than 17.5 µm, which meets the specification of less than 50 µm. This means that passive self-alignment using a through-hole formed under the optimized DRIE conditions can be exploited to make OBSAs without requiring optical alignment of mirrors and lenses.