Radiation Education with Radon Detector
Tomo Nakajima, Takafumi Niida
Introduction

Contact

After Fukushima nuclear plant accident occurred in Mar 2011, radioactive
material flied to wide area in Japan through the wind. It was not until a people
faced problems about radiation that the lack of radiation literacy wasrevealed. People need to learn the basic knowledge about radiation. At present
radiation education is reconsidered in Japan. Though there is the guideline forhigh school education, in which GM-counter is introduced as an example ofradiation detector, it’s not enough to understand the properties of radiation
like a decay of nuclei and half-life. So teaching materials to make it possible forstudents to learn such properties are needed.
In this poster, we present a radon detector as a teaching material, whichhave been developed to be effective in education.

Development of Radon Detector
Radon detector system we have developed consists of 4 parts, which is designed
to be easy to understand and simple to make by hands.

Radon detector system
Detectionof Rn

University of Tsukuba

Pulse HeightAnalyzer

DataControl

DataCollection

Tomo Nakajima : s1120062@u.tsukuba.ac.jp
Takafumi Niida : s1030089@u.tsukuba.ac.jp

Characteristics of Radon Detector as a Teaching Material(1) Able to measure α-ray energy and half-life(2) Able to identify nuclide of radioactive elements(3) Easy for students to make detector by themselves
Radiation education with our radon detector leads to the understanding ofradiation and gives a good opportunity to learn the mechanism of softwareand hardware in a system. Active learning consisting of making detector,
measurement, data analysis and discussion leads to the promotion of theability of treating and understanding the information correctly andproblem-solving ability of students. It’s also easy to handle in high school
because radon exists naturally around us and we don’t need any
radioactive source. And we are improving it to be low cost and compact
for the wide spread through high school.

Results of Radon Measurement

Detection of Rn
Electrostatic collection method is adopted to catch daughter nuclei decaying
from Rn. PIN-PhotoDiode(s3590-09,HAMAMATSU) is used for measuring α-ray.

Radon gas collected from ores includingnatural uranium was measured for theperformance check of our detector. Fig.1
shows the measured energy spectrum of α-ray.
Two peaks can be seen, which correspond toα-rays emitted from 218Po and 214Po. Energyresolution(ΔE/E) is about 1.1% at 7.69[MeV].

Pulse Height Analyzer
Pulse height analyzer is composed of pre-amplifier,
218Po+
Photo Diode（-600V）
shaper-amplifier, comparator and sample&hold, which
214Po+
are on the same circuit board with high voltage power
218Po+
supplier. Comparator gives a trigger signal to222Rn
microcomputer called Arduino©. And an interrupt
program in the Arduino starts up and sends gate signal
to sample&hold. Then sample&hold holds the pulse height of the signal.

218

Po

214

PoFig.2 shows the count rates of 2 peaks inFig.1 as a function of the time. Solid lines
indicate fit function obtained by thesolution of the differential equations in thebelow. Both count rates decrease according
to the half-life of 222Rn. Half-life of 222Rnby fitting are 3.9 days for red symbol and3.8 days for blue symbol. Fig.3 shows thecount rates around the start time.

Fig.2

Fig.3

222Rn:

dN1 = -λ1N1dt
218Po: dN = (λ N - λ N )dt
2
1 12 2.....

Photo DiodecircuitShaper Amp(CR-RC-CR)

Fig.1

214Po:

dN4 = (λ3N3 - λ4N4)dt(214Po ~ 214Bi)

Comparator

Pre AmpImplementation

DC converter

Implementation of radiation education have been performed for highschool students and university students so far.
Sample&Hold

Data Control and Collection

HV module

Pulse height is converted to digital data by 10bit ADC within Arduino©. Arduino
is a 8bit microcomputer and the open source hardware and software. Then thedigital data is sent to PC via USB port. In PC, the sent data is processed by theProcessing© application. Processing is also the open source programming language,
which is mainly used for graphic design.
Trigger

Pulse
HeightAnalyzer

ProgramPC
ArduinoOnline monitoring system
GateProcessing
Pulse height

Digital data

Cost：about ￥30,000 (≒300€)

Outlook✓ Cost down to ￥10,000 (≒100€)✓ Evaluation of the detection efficiency✓ Implementation at high school with improved detector

Display(Two thirds of the cost comes from photo diode and HV module.)References

1) S.Tasaka, RADIOISOTOPES. 46(1997)710
2) Y.Takeuchi, et al., Nucl. Instr. Meth., A 421, (1999) 334