 |
 |
 |
||
 |
 |
 |
||
|
|
Column No.3 Safety and Nemoto - (1) "Smoke detectors" (November 30, 1999)It is often said in Japan that there are four things all people dread: Earthquake, Lightening, Fire, and Father. Fathers, perhaps, have become much less fearful nowadays but Earthquakes, Lightening, and Fire can still be horrific. Earthquakes and Lightening are natural disasters that cannot be controlled by humans but Fire can be prevented. Nemoto is a company that has developed technologies used in preventing fires!  In years past, many fires resulted in disaster simply because of delays in detection. In the 20th century, fire alarm systems were developed which were capable of detecting fires without the aid of the human eye. Initially, they were installed on ceilings to detect increases in ambient heat, however the first detection systems were only capable of detecting fires of a certain scale. Earlier detection would require a system capable of detecting the smoke that is generated before a fire flares up. As a result, smoke detectors were developed. There are two kinds of smoke detectors. Photoelectric smoke detectors which actually detect inconsistencies in the permeability of light and ionization smoke detectors which detect slight variations in electric current caused by the ionization effect of a radioactive substance. Ionization type smoke detectors are much more widely used (See Figure 1) as they have a higher sensitivity while remaining accurate over a wider range of smoke types and colors. Cerberus Corporation of Switzerland was the first to develop an ionization type smoke detector. Japanese companies wanted to develop competitive products. In 1966, several Japanese detector manufacturers asked Nemoto to develop a radiation source for an ionization type smoke detector. Nemoto initially used the technology it had acquired though use of radioactive self-luminous pigments to designed a sealed radiation source that utilized Radium's alpha rays. This initial radiation source was well accepted by the market, but Nemoto continued its efforts to develop even better radiation sources.  In 1970 63Ni, which was both safer and less expensive than Radium was adapted for use in smoke detectors. Two years later, when it was learned that 241Am was an even a safer radiation source, this became the de facto radiation source smoke sensors. In 1977, Nemoto added several electrical engineers to its R&D department and began work on the development of its own smoke detectors. This effort led to the mass-production of a new smoke sensor [NIS-09](Figure 2). The novelty of this sensor was that it used a single radiation source for two chambers, which halved the radioactive emission of conventional smoke sensors.
In addition to supplying smoke sensors, Nemoto produces and exports portable smoke detectors with their own circuit design, such as the one combined with an alarm clock as well as cigarette-pack-sized portable smoke detectors called "Smokie". (See above photos)  The latest development out of Nemoto's R&D Labs is the new high performance sensor (NIS-05A) that currently has the lowest radioactivity level in the world (241Am 18.5kBq). This sensor has seen excellent market acceptance and is rapidly gaining market share. (See photo at left) Nemoto's current R&D efforts are geared towards developing smoke sensors that emit even less radioactivity than 10kBq, the exemption level stated in BSS (Basic Safety Standard)*1. Footnote) *1 BSS exemption level : The radioactivity that may be exempted from the regulations of Radioisotope International Basic Safety Standard "Safety Series No.115" published by IAEA (International Atomic Energy Association) in 1996. The exemption radioactivity level of 241Am is defined as 10kBq. ** Reference link: IAEA 1996 Publications |
