Development of a Landmine Detection System with Nuclear Sensors

INDEX

1. Introduction
2. The problem of landmines
3. Types of landmine
4. Current detection method
5. Nuclear LMD
6. How nuclear LMD works
7. Future detector
8. Application
9. Advantage
10. Conclusion

Development of a Landmine Detection System with Nuclear Sensors

The problem of landmines in Egypt and the detection techniques currently used for deminingare described and discussed. Most of these techniques depend on metal detectors. This makes the demining ofvast areas of contaminated lands difficult, dangerous, slow and very costly processes. Although some of thesetechniques are very effective to locate metal or metal like anomalies, but they suffer from high false alarm ratesbecause they are not capable to identify these anomalies as mines. However, in the last four decades, techniquesbased on using neutrons of different energies have proved themselves as powerful tools for elemental analysis andare therefore capable to identify explosive materials and to confirm the presence or not of a landmine.Nuclear techniques based on measuring the density variation of hydrogen by measuringthermal neutrons backscattered from buried object are given and discussed. In addition, the use of two nuclearsensors with other two sensors based on EMI and GPR in an integrated system with data fusion and how tointegrate these sensors onto a land vehicle are described and discussed.

1. Introduction

Egypt is the country with millions of landminesresult of extensive combat operations between alliedand axis forces during World War II that took place between December 1940 to May 1943.UNICEF estimates that about 23 million landmines

and unexploded ordinances have been leftfrom the World War Two Campaigns [1]. Thesehidden killers are scattered over 3902 minefieldsin the Northern part of the Western Desert ofEgypt, left behind by the troops of Germany,Italy and the allied forces led by Britain battlingfor the control of North Africa in the 1942 Battleof El-Alamein. These abandoned landmines ravaging270’000 Hectares of pastoral and agriculturallands between El Alamein and the Libyanborder. Other 6 million landmines are buried inlarge number of minefield spread in the Northernand Western parts of Sinai, Suez Gulf and WesternCoast of Red Sea. These buried landminescontaminate _25’000 Hectares of lands in Northernand Western parts of Sinai.The buried landmines in these vast areas ofthe Egyptian lands killed and maimed more than10,000 civilian persons during the last six decades.The effect of these hidden killers on survivors isdevastating and the threat is real and lasting. It

has a very serious social and economical impact,but it is considered first and foremost as a humanitarian problem. Egypt needs to clear thecontaminated areas at least $ 300 million for initiatingand starting national projects in agriculture,industry, tourism and for oil and gas exploration.More than $ 30 million was spent to

clear nearly one tenth of the total contaminatedareas. The mine clearance should not go slowlyas it is now, but requires international efforts andsupport especially from the countries involved inWorld War II.

2. Currently used Detection TechniquesIn Egypt, the humanitarian de-mining activities,carried-out to remove landmines from thevast contaminated areas are not on the same levelof the problem. The conventional methods whichare used, such as metal detectors, magnetometersand ground penetrating radar, etc., make the

procedure of removing this great numbers of landminesvery slow, inefficient, dangerous and costly.In addition, most of these detectors can not distinguish

a mine from metallic debris, and in caseof metal detectors, the extremely high false alarmrate, only one out of about one thousand alarmsturned out to be a landmine. This results in arather inefficient, costly and slow operation.

3. Developing and Adopting Nuclear TechniquesResearch activities are running to develop theabove-mentioned nuclear techniques since the beginningof the IAEA TC project in 2003. In caseof detection by thermal and fast neutron analysis,no progress was achieved due to lack of a neutronsource with energy high enough to detect Carbonand Oxygen. However, for hydrogen densityvariation measuring technique the activities runningin collaboration with the University of Delftusing the DUNBID system have achieved resultsthat are promising for landmine detection in aridcountries like Egypt . The measured backscatteredthermal neutrons using this system wereused to reconstruct 2D images for the tested objects.Some of them are displayed in pic.These 2D images make it possible to recognize the

presence of buried objects with different moderatingelements. Also the count rates of thermalneutrons back-scattered from plain soil and soilembedded with the tested objects buried at differentdepths were used to plot the attenuationrelations given in Fig. 4. These relations are plottedas net count rate, (count with object – countfrom plain soil) versus soil depth in cm. It is quiteclear from these relations that, the DUNBID systemcan easily detect and distinguish small APmines with 100 g explosive buried at depths downto 15 cm. The plotted attenuation relations also

show that, the system is capable to distinguish, between hydrogen containing objects and othersof higher density buried at depths down to 20 cm.However, the main limitation of the system is theun-capability to distinguish between objects ofnearly the same hydrogen content.

4. Weighting of Metal and Nuclear SensorsEMI provides capabilities to detect and allocateall types of landmines very fast but lacksspecificity. GPR provides capability for decidingwhether anomalies showing low metal contentare mines or can be disregarded as metal clutter.NHBS provides capability for identifying plasticland mines of low metal content. PFTNA provideselemental based identification of explosives.This will be needed to resolve the most difficultcases, namely those in which the decision betweenlandmine and no landmine cannot be made fromthe information provided by the previous sensors.If metal clutter is prolific in the region that isbeing demined, a simple two sensors system consistingof EMI as a location sensor and PFTNASas a confirmation sensor will probably be inefficient.

The low speed response of PFTNA willlimit its ability to deal with large numbers of falsealarms (due to metal clutter) fed to it by EMI.Incorporating additional sensors in the integratingsystem can reduce this problem. For exampleGPR or NHBS can be used to filter out clutter eitherby imaging by GPR or by identifying plasticland mines with NHBS sensor, among the anomaliesdetected and localized by the EMI sensor.

Nuclear Method Of Landmine Detection

The Problem: Landmines

There are nearly 50 million unexploded landmines in 60 countries around the world.

These landmines causes approximately 10,000 deaths per year.

Large portions of land goes unused due to fear of mines.

Geopolitical

Landmines kill and maim long after the war is over

90% of those killed are civilians

 It costs ~$3 to place a mine

It costs $300 to $1000 to detect it and remove it

Many victims are children

Modern Mines:

Modern mines can be constructed with plastics and composites.

The low metal content of mines makes detection extremely difficult.

Current Detection Methods:

•Metal Detectors

A metal detector is a device which responds to metal that may not be readily apparent.The simplest form of a metal detector consists of anoscillator producing an alternating current that passesthrough a coil producing an alternating magnetic field. Ifa piece of electrically conductive metal is close to thecoil, eddy currents will be induced in the metal, and thisproduces an alternating magnetic field of its own. Ifanother coil is used to measure the magnetic field (actingas a magnetometer), the change in the magnetic field dueto the metallic object can be detected.

•Ground Penetrating

Radar (GPR)

Ground penetrating radar

Conventional metal detectors rely on electromagnetic signals with frequencies of the order of 10–100kHz, which are not sensitive to plastic or wooden mine bodies and the high explosive block itself. The only part of a low-metal mine that they may be able to detect is the detonator. Much higher frequency signals (of the order of 1GHz) are employed in Ground Penetrating Radar (GPR) and these signals are also sensitive to the non-metallic parts of the mine. Unfortunately, as they are also affected by innocuous objects such as tree roots and stones and by local changes in soil moisture, it is difficult to distinguish a mine on a GPR image.

•Probing

•All the methods above canbe extremely dangerous.

• By Animal:

Dogs

Well-trained dogs can sniff out explosive chemicals like TNT in landmines, and are used in several countries.

Rats

Like dogs, Giant pouched rats are being trained to sniff out chemicals like TNT in landmines.These rats are currently working in minefields in Mozambique and are trained in Tanzania by APOPO. The rats are called HeroRATS.

These animals also have the advantage of being far lower mass than the typical human. They are less likely to set off small mines intended to injure or kill people, if the bomb-sniffing animal crosses directly over the top of a buried mine.

The Solution:Nuclear LMD

Introduction:

Nuclear detection

There are two principal techniques to detect land mines through nuclear reactions. Both rely on the use of neutrons.

The first such technique relies on the fact that the vast majority of explosives used in land mines are very nitrogen rich when compared with other materials. To detect such anomalies one may make use of the nuclear reaction

14(n, γ)15N (10.8 MeV)

In practice a detection system using this reaction works by subjecting the mine to thermal neutrons while searching for the characteristic gamma ray emitted from the excited state in nitrogen-15; these photons will only be observed when an object containing nitrogen is being subjected to the neutron irradiation.One possible neutron source is californium-252 which undergoes spontaneous fission. A better neutron source is to use a sealed tube electrostatic D-T neutron generation tube, this has the advantage that the tritium is much less radiotoxic than the californium so in the event of an accident such as an explosion the nuclear mine detection equipment would pose a smaller threat to humans. This type of explosive detection has been proposed for use in airport security and for the detection of explosives in trucks coming into military bases.

An alternative way of spotting land mines through nuclear reactions with the help of neutrons is that of measuring the thermalization of neutrons. In this technique the soil is irradiated by fast neutrons and the flux of thermal neutrons scattering back is measured. The motivation for this technique is that explosives contain much higher concentrations of hydrogen, which is a very effective moderator of neutrons.

The Physics:

•The detector uses both thermal and fast neutrons to cause gamma ray emissions from N,O and H.

•A gamma ray spectrometer can then be used to determine if the concentrations of N and O are high.

•The neutrons can be produced by either D-T fusion or radioisotopes.

How it Works:

All explosives have high concentrations of both N and O.

By shooting neutron into the soil concentrations of N,O and H can be determined.

The concentrations of N and O is high in a particular area, this is likely an explosive.

Future Detectors:

… will likely be robotic and combine nuclear detection techniques with GPR and GPS.

This combination will allow for extreme accuracy and speed with minimal false alarms.

Other Application:

• There are several research groups around the world currently working on ways to use NQR to detect explosives.
• Units designed to detect landmines and explosives concealed in luggage have been tested.
• A detection system consists of a radio frequency (RF) power source, a coil to produce the magnetic excitation field and a detector circuit which monitors for a RF NQR response coming from the explosive component of the object.

Airport Security:

The same technology used in nuclear LMD can also be used to scan luggage in airports.

This technology will allow faster and far more accurate scanning of luggage.

The Future:

Despite global political movements and treaties the global landmine and UXO threat is increasing

ADVANTAGE:

An Effective Detection System Would Save Lives and Money

1. Save up to two-thirds of $14-50 billion mine clearance price tag.

1. Prevent millions of casualties among civilians and deminers .
2. Create potential spin-off benefits

airline explosive detection

signal processing

underground imaging

medical imaging

Conclusions and Recommendations:

Thermal neutron back-scattering techniqueshows reliable results that are encouraging to use a device based on this method as a nuclear sensor for detection of hydrogen containing objects including landmines. Such a device will tend to reduce the number of false alarm rate given by metal detectors. International co-operation will help Egypt to develop novel detection techniques, not only to overcome the most dangerous problem, but also will make Egypt capable to take the technical lead for assisting regional countries in similar conditions.

Reference

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