Endüstriyel Atık Malzemesi Olan Kağıt İle Bor Elementi Kullanılarak Nötron Zırhlamasında Etkili Bir Zırh Geliştirilmesi

Abstract

Radyasyon etkilerinin canlılar üzerinde yarattığı büyük tehlikeden dolayı, nükleer enerji kullanılmasında radyasyon korunmasına büyük önem verilmiş ve çeşitli zırh- lama teknikleri ile zırh malzemeleri geliştirilmiştir. Bu amaçla geliştirilen zırh malzemesi, nötronların zırhlama işleminde endüstriyel atık malzemesi olan kâğıdın kullanılmasıyla gerçekleştirilmiştir. Kâğıdın endüstriyel alanda kolayca kullanılabilen ekonomik bir malzeme oluşu ve yüksek oranda selüloz (C6H12O5) hammaddesini içermesi onu seçici kılmaktadır. Kâğıdın zırh malzemesi olarak başlı başına kullanımı zırhlama tekniğinde yetersiz kalmaktadır. Bundan dolayı katkı malzemesi olarak bor elementi gibi nötronları fazla sıyla zayıflatan yeni bir zırh malzemesi geliştirilmesi amaçlanmıştır. Katkı malzemesi olarak seçilen bor elementinin nötron yutma tesir kesidinin yüksek, yakalama reaksiyonunda yayınladıkları gama enerjisinin düşük olması kağıt ile iyi bir zırh malzemesi oluşturmasını sağlamıştır. Deneysel çalışmanın ilk aşamasında sadece kağıt mal zemesinden sayımlar alınmış ve nötronların en fazla soğu rulduğu zırh kalınlığı seçilmiştir. Bu zırhlama etkisinin aynısını veya fazlasını daha az kalınlıkta zırhlama malzemesi kullanılarak gerçekleştirmek amaçlanmıştır. Farklı konsantrasyonlarla hazırlanmış zırh malzemesinden sayı mi ar alınmış ve ideal zırh kalınlığı belirlenmiştir. Kağıt malzemeye katılan borik asidin nötronlara karşı zırhlama yeteneğinden yararlanarak daha az kalınlıkta bir zırh malzemesi geliştirilmiştir. Düşük konsantrasyonlarda borik asit kullanılarak daha ince kağıt ile oldukça etkin bir zırh malzemesini üretmenin mümkün olabileceği görülmüştür.

Nowadays, the use of radiation and radioactive materials increases rapidly and the field of applications spreads widely. Because of the increasing of the usage of radiation, several radiation risk factors come along in it. Radiation effect on living things is so important and dangerous. Therefore to protect the human being from the radiation, the most important factor is shielding. New shielding techniques were developed for the protection of radiation. The use of shielding makes the possibility of usage of radiation all over the world. Of course for the development of shielding, the type and the activity of the radiation should be known. It was the main aim of this work to develop a new shielding materials for neutrons in order to protect the living tissues from radiation. In this work, neutrons from Howitzer neutron source (NH-3) produced by (a, n) reactions used. Experimental set up in this work, made from neutron Howitzer, BF3 detector, high voltage supply, amplifier and counting system. The body of neutron Howitzer source contains an irradiation canal in which BF3 detector and shielding material are placed. The BF3 detector is placed behind the shielding material for counting the neutrons, penetrated from the matter. The BF3 detector which is placed inside of the neutron Howitzer source is connected to high voltage supply and amplifier. The detector that takes the voltage from the high voltage supply transforms to voltage signals in itself. Because of the weakness of these signals amplification became necessary and the amplifier used for this purpose. In this work, it was aimed to use the paper in order to use the industrial residual material for the process of neutron shielding. Different quantities of the paper are chosen because of their inexpensive and widely uses in many industries. The most important reason for choosing the paper material in this work is its components. The paper material is formed by high percentage cellulose (C6H12O5). As it shown in the cellulose chemical formula, carbon and especially hydrogen elements are in large amount which makes the cellulose has a big advantageous to slow down the neutrons. For the shielding of the neutrons, the industrial residual paper are used with bor element to produce a new cheap material which is not being tested before. Bor element is not found by naturally and also it is not an element that is found in the crust of earth. However Turkey is one of the top countries that is so rich with underground bor element sources. The main criteria of choosing of additive materials should have high neutron absorption cross section and the low energy gammas emitted in the capture reactions. It was observed that in this conditions bor element with the paper material can be the best shielding for neutron protection. The aim of this experiment is to form an ideal shielding material by using bor element and paper materials together. Therefore the produced shielding is going to reduce the intensity of radiation by absorption. Generally, instead of stopping radiations completely it is preferred reducing their intensities into maximum permissible level. After getting positive results from developed shielding material, it is planned to produce a new shielding material. In the first stage of experimental work, it is aimed to know how effective the paper material is as a shielding material against neutrons without using any other additive elements. Since paper material is found to be not effective vi enough for neutrons by itself in the shielding techniques it is planned to used bor element as an additive material. In the stage of preparing shielding material, boric acid solution has been made in different concentrations (0,25, 0,5, 0,75, 1, 3%), and different amounts of bor elements were used. Paper material in different solutions has been absorbed by different chemical reactions and thus the shielding material has been formed. Different levels of boric acid are worked in order to find the ideal amount of boric acid concentration to mix with paper material. Separate shielding material is prepared for each boric acid concentration levels. The counts taken from the paper material are examined, and it was satisfactorily observed that absorption of neutrons were increased as the paper thickness increases. But one of the aim of this work is to form thinner and more effective shielding material against radiation. First of fall the counts are taken from the shielding material having 0,25 % boric acid concentration and these counts are seen more effective in neutrons shielding comparing with the paper material. Increasing the thickness of shielding material having 0,25 % boric acid concentration, the increasing is observed in absorption of neutrons. It is observed that effective results to absorb neutron are achieved the paper material with 0,25 % boric acid concentration paper when compared with some thickness, and without the boric acid. But the differences between them are not in great values. In order to form more effective shielding material comparing with the paper material the more boric acid concentration is needed. Therefore, shielding material having 0,5 % boric acid concentration are prepared when the results are compared with different shielding materials having 0,25 % boric acid concentration observed the values more effective. When boric concentration is increased to 0,75 %, similar Vll improvement are observed comparing with 0,25 % and 0,5 % boric acid concentration. These different boric acid concentrations (0,25 %, 0,5 % and 0,75 %) couldn't absorb neutrons at the desired level. When compared with the paper material it is found that the great differences are not shown on different boric acid concentrations. When boric acid concentration level is increased to 1 %, very different values are observed compared with 0,25 %, 0,5 % and 0,75 % boric acid concentration used in shielding materials. Increasing the thickness of shielding material, the high values of absorption are observed. These high values for absorption of neutrons show that how effective the boric acid is in the paper material. The shielding material having 1 % boric acid concentration proved that absorption neutrons are more effective than 0,25 %, 0,5 % and 0,75 % boric acid concentration. This results leaded to measure the results from 3 % and 5 % boric acid concentration. The results are taken separately for 3 % and 5 % boric acid concentration. When these counts are compared with 1 % boric acid concentration different absorptions were seen. Differences of concentrations in shielding material gives very similar absorption results and therefore there is no need to use the high concentrated sampled. Finally, it was thought that 1 % boric acid concentration is preferable. The usage of 1 % boric acid concentration, shielding material is more economical than the other higher level concentration shielding materials. The main aim of this work is to use the shielding material developed in the industrial field. 1 % boric acid concentration is chosen because all three types of concentration (1 %, 3 % and 5 %) give similar results. After choosing the ideal boric acid concentration level the last stage of experimental work is to decide the ideal thickness of neutron shielding material. This is done viii by the help of the results of thickness of papers and the boric acid concentration. First of fall, it is found that 90,4 % neutron absorption observed by using 5 cm thickness of paper material without any additive materials. The final aim of this work is to achieve the same or higher level of shielding with thinner shielding materials. Then it is started to use different boric acid concentrations with different thickness of paper material and different level of boric acid concentration the shielding material which is formed in this thickness and concentration showed the absorption of neutron in 95,5 %. Since success of shielding for neutrons it is found to be sufficient to use 1 % boric acid concentration instead of using 5 cm thickness of paper material by itself. As a result thinner shielding material is achieved by using effectiveness of boric acid concentration as a shielding to absorb neutron with paper material. Therefore it is possible to produce effective shielding material by using lower concentrations of boric acid with a thinner paper.