Nuclear Radiation Detection Through motes

This article is not to debate on whether the nuclear energy is needed or not. Nuclear energy has become part and parcel of our day-to-day lives. For the ever-growing power needs, nuclear energy seems to provide some good answers to it. As of 2008, India has 17 nuclear power plants generating 4,120 MW and six units of 3,160 MW are under construction (Source: Reuters). It is India’s goal to expand its nuclear power generation capacity to at-least 20,000 MW by year 2020 and it is confirmed by (IANS) Atomic Energy Commission (AEC) chairman Anil Kakodkar on Feb,18, 2009.

Effects of radiation levels on humans

Here comes the safety question. How to safeguard the individuals from being affected by nuclear radiation? Nuclear Energy is like friction, a necessary evil. According to "Nuclear Arms Race: Craig and Jungerman, 1990" a dose-rem (roentgen equivalent man) of 5 and above cause damage to human health. Please refer to the following table on the effects of human body due to nuclear radiation.

Gold Leaf Electroscope – Detecting Radiation – Why it is ineffective?

Becquerel invented the 'Gold leaf electroscope' right after the discovery of radiation. He used the concept of ionization of gases to detect radiation in a region. Gold leaf electroscope consists of a metal rod (R) with two small gold foils (G). The metal rod is connected to a metal plate (P) at the upper end. The rod is help by an insulating bush (B) and kept inside in a glass (G) or earthed metal box to protect gold leaves from air currents (refer fig1).

An electric charge is applied to metal plate (P). Since the charge on the both leaves care the same. They repel each other to form an inverted 'V' shape. When the electroscope comes to contact with radioactive area, the gold leaf starts losing the charges and slowly comes back to the normal position. The amount of charge diffused indicates the level of radioactive radiation present in the area.

Eventhough, this simple apparatus can detect radiation effectively, it still needs the human agent to carry the equipment to radiation affected area to detect radiation. Even with highly effective shielding one cannot save the life of humans in a lethal radiation scenario. The major drawback of this mechanism is that it cannot guarantee the life of the human agent carrying the instrument. In crude cases, the scientists determine the effects of radiation by the number of dead agents reported that carried those equipments.

Radiation detection using Motes:

Let me take this opportunity to provide a quick introduction on motes. Motes are small, low powered and cheap computer connected to several sensors and a radio transmitter capable of forming ad-hoc networks (Mesh). They can integrate with different kinds of sensors to measure light, acceleration, position, stress, pressure, humidity, sound, vibration, radiation and others. They transmit data using radio links between one another. The transmission range is usually from 10 -200 feet. They use ultrasound frequency for transmission. They can derive power through 'AA' batteries, solar power, vibrations and magnetic fields emerging from power lines.

Motes have a real-time programmable OS known as TinyOS (www.tinyos.org). It requires only 8KB of memory and does have built-in mechanism for power savings and multi-hop networking. TinyOS can be reprogrammed easily and hence the motes can be reprogrammed at any given instance of time.

System Design
In this scenario, two types are motes are developed; Type 1 and Type 2 devices.

Type 1 devices will be installed in some fixed known locations on a safer locus around the radioactive area. These units will transmit pre-synchronized time data for location identification. These units will be well shielded and can be reused. They have wireless capabilities and transmit data using wireless networking.

Type 2 devices are installed on ad-hoc basis or pre-installed or sprayed from an aircraft in the radiation affected areas. These units will transmit the radiation data. The units will have a sensor that is based on MOSFET (Metal Oxide Semiconductor) radiation detection to identify the level of radioactivity. These units will run TinyOS based application and shall transmit the data to the neighboring motes using Radio Frequency.

Type 2 devices form an ad-hoc mesh networking to transmit the data across each other using motes technology. The Type 2 devices shall forward the information to Type 1 devices and remote handhelds using RF. Type 1 devices further transmits the data to application running on handhelds or workstations using wireless networking.

The remote handled application shall have the capability to directly interact with the Type 2 device motes using RF and with Type 1 devices using wireless networking. The Type 1 devices will provide the location information of the Type 2 devices to the handheld application. The Type 2 devices directly or through Type 1 devices will provide the handheld application about the radiation level. The handheld application will provide the online display of the type of radiation, radiation intensity and half life calculation on a map. It also provides trend curve based on history on the activity.

Why Motes based radiation detection is a better solution?

With the advancement in technology, every care should be taken to save human lives. Motes provide the mechanism to determine the radiation levels of the affected areas without the requirement of any human agents walking into those areas. Also the level of intensity can be measured with ease from a remote location and appropriate steps could be taken to contain the radiation. The motes based system does provide the solution to real-time monitoring. Why not take the capabilities of real-time monitoring and alerting rather manual intervention to detect radiation? At end of the day, every life is valuable. Why not provide a system to take extra precaution to safe guard human lives? As wise would say "Prevention is better than Cure" and I do hope Motes will help prevent radiation based hazards.