IP GLOGE 2013 - RADIOATTIVITA'

 Fonte: https://moodle.usal.es/course/view.php?id=9764 (11.07.2013 ore 18.34) 

Dopo un po’ di tempo riprendo a scrivere sul mio blog. Questa volta per raccontarvi della mia esperienza che sto vivendo proprio ora (7-20 luglio 2013) a Salamanca (Spagna). Ho preso infatti parte ad un progetto chiamato “IP GLOGE 2013”, un Corso Erasmus Intensivo organizzato dalle università di Ferrara, Coimbra (Portogallo), Budapest (Hungary) e Salamanca. Al corso, svolto in lingua inglese, hanno preso parte in tutto 4 italiani, 6 ungheresi, 5 portoghesi e 3 spagnoli con altrettanti professori .

 L’obiettivo del progetto “Global Heritage and Sustainability: Geological, Cultural and Historical” è, oltre che lo scambio interculturale di conoscenze tra i vari partecipanti, quello di studiare le rocce dal punto di vista culturale e storico oltre che da quello strettamente geologico, al quale noi geologi siamo abituati a fare . Gli argomenti trattati sono molteplici e li scopriremo piano piano. Inizio però già nel pubblicare la mia prima relazione riguardante la radioattività dove abbiamo potuto osservare le diverse emissioni di radiazioni che le rocce emettono (ignee, sedimentarie e metamorfiche). 

Group report

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Natural radioactivity in different natural

stones

Theoretical Introduction

All natural rocks contain minerals that have radioactive elements in their constitution, even

if they are only present in insignificant amounts. Three important elements to the study of

radioactivity are Potassium (K), Thorium (Th) and Uranium (U), but only the isotopes 40K, 232Th,

238U/235U are radioactive, which means, they release radiation - α, β and γ radiation. We usually

measure this radiation in Becquerel (Bq), which is a measure of the physical/real amount of

radiation. We can also use Sievert (Sv), which measures the biological effect of radiation.

When working in the field of radioactivity one should never forget the importance of radon –

a noble gas that is involved in the decaying of 238U and is harmful for the environment in high

doses.

Purpose of the experiment

• Learn the techniques/methods used to measure radioactivity, as well as, learning which apparatuses/equipment are better suited for this kind of work.
• Measure the natural radioactivity (in counts/minute*) of 38 different kinds of rocks – (igneous, metamorphic and sedimentary rocks).
• Compare the data acquired (on a table) on the experiment, in terms of radioactivity, with the three different groups of rocks.
• Brief explanation, at the end of the main experience described above, of how to measure the amount of the qualitative radon being released from rocks (granites).

This is done specific equipment that we will talk about later on the Procedure.

Procedure

Using the equipment shown on the picture below (Figure 1), a Geiger-Muller counter, we

measured the amount of radiation (α, β and γ radiation) associated to the 38 rocks of the

experiment.

Figure 1 - Geiger-Muller counter 

On the second part of the class, we simulated a routine experiment for measuring the

amount of radon in rocks. Radon has a half-life of 21 days. We put the rock into a special and

sealed container (Figure 2) connected to an alpha pump and alpha guard professional radon

monitor. After those 21 days we would be able to measure directly the amount of radon 222Rn in

the air, because it is equal to the quantity of 226Ra in the rock – isotropic equilibrium.

Figure 2 – sealed container connected to an alpha pump and alpha guard professional radon monitor

Results

The results of this experiment are displayed through a graphical way, on the table below

(Table 1). Together with the results, there are some representative photographs of certain rocks.

Table 1 – Measurements of rock’s radioactivity

We took a photograph of four rocks, from the different rock groups (Figure 3)

Figures 3 – Different types of rock, in order: Igneous, metamorphic, sedimentary (limestone) and

sedimentary (carbonate) 

Discussion of the results 

Graph 1 – Graphical representation of the measurements of rock’s radioactivity

The natural radioactivity of several different rocks was examined. The radioactivity was

measured with Geiger-Muller counter. According to the measurement the igneous, metamorphic

and sedimentary rock have different radioactive emission. It is in great agreement with the

presumptions. The values of radioactivity measured were higher to the igneous rocks (150 Bq –

the highest), and lower to the sedimentary rocks, particularly in the limestones (30 Bq – the

lowest); the metamorphic rocks showed high levels but still lower than the igneous (Graph 1).

Graph 1 – Graphical representation of the measurements of rock’s radioactivity.

The background radiation (including natural and industrial) affects the human health, so the

radiation of the residential building needs to be controlled. The radioactivity might be higher if the

surrounding rock is mainly igneous, so we need that the buildings are constructed in a way that

considers Radon emission of the surrounding ground. Furthermore, the building materials itself

have a radiation.

This thought leads us to the significance of the radioactive emission of the stones: in certain

areas the radioactivity of the ground or the building materials is an important aspects of design.