Sper Scientific 840007 User Manual

RADIATION MONITORS

840007, 840026

INSTRUCTION MANUAL

SPER
SCIENTIFIC

TABLE OF CONTENTS

INTRODUCTION ....................................................... 2

CAUTION .................................................................. 2

BATTERY REPLACEMENT ...................................... 3

OPERATION ............................................................. 3

READINGS ................................................................ 5

INTERPRETING READINGS .................................... 6

SPECIFICATIONS ......................... ................... ......... 11

LIMITED WARRANTY ............................................... 12

NOTICE ..................................................................... 12

INTRODUCTION

This manual contains valuable information about the nature
of ionizing radiation that should be understood by the user
so that accurate measurements can be made. Information
on the care of your Geiger counter is also included. If the
following instructions are followed, your radiation monitor
will give you many years of reliable service.

The radiation meters are very sensitive pieces of equip­ment. Although housed in a high-impact case, the Geiger­Mueller tube that senses radiation is fragile. If the unit is
dropped, the G-M tube may break. Exposure of the unit
above 40°C (100°F) may also cause the G-M tube to stop
functioning. The electronic circuitry is sensitive to high hu­midity (over 90% R.H.).

CAUTION

DO NOT put the unit in a very hot place (such as a car's
glove box, especially on a summer day).

DO NOT allow the unit to get wet. However, if this should
happen, clean it with a towel and allow unit to air-dry for
several days (do not place in an oven or microwave).

DO NOT open the unit (except for battery replacement).
There are no adjustments inside for the 840007 that can be
made by the user, since the unit is calibrated at the factory.
For the 840026, see instructions on page 5.

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BATTERY REPLACEMENT

The unit is powered by a 9-volt battery. With the on button
activated, the LED should be brightly lit. When the LED is
no longer bright or when the LED dims in the presence of a
radiation source, replace battery. To replace the battery:

1. Slide the plastic door off the unit located in the back.

2. Carefully replace the battery. DO NOT reach into the
unit through the battery compartment while unit is on.
G-M tube activation voltage is over 200 VDC.

3. Replace plastic door.

4. For extended operation and infrequent battery replace­ment, use an alkaline battery.

OPERATION

The radiation monitor only operates while the push button
on the face of the unit is depressed. This feature makes the
operation very simple and conserves battery power. The
unit is designed to be held in the right hand, with the thumb
over the pushbutton (see Figures 1 and 2). The LED just
above the pushbutton indicates that the unit is on and will
give an indication of battery condition.

When the unit is turned on, a faint buzz may be audible in a
quiet room. This is normal and is caused by the transformer
that powers the G-M tube.

In most parts of the world, background radiation will cause
the speaker to click at random intervals, about one click
every few seconds. In areas where large deposits of natu­ral radioactive minerals are found, or in an area that has
been contaminated with radioactive materials, the speaker
will click more frequently. This is called the "background
level." It should be taken into account when making meas­urements on specific objects.

Since the incidence of clicks from radioactive sources is
random, several clicks can be heard in rapid succession,
while on other occasions several seconds may elapse be­tween clicks. This is normal. Averaged over a period of
time, the click rate should remain relatively constant. A rea-

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sonable average time should be at least two minutes or
more.

The Geiger-Mueller tube is located behind the slots in the
upper edge of the case. The surface of the tube is very thin
(0.004"). This allows beta radiation to penetrate and to be
detected with greater efficiency. (Beta rays and other types
of radiation will be discussed in the next section). This thin
surface is fragile and poking sharp objects through the slots
will damage the tube.

Your Geiger Counter is designed to be sensitive to:

1. Gamma radiation (which includes X-rays).

2. Beta radiation.

FIG. 1

Gamma radiation and X-rays can penetrate the plastic case
with comparative ease.

Beta radiation can most efficiently enter the case through
the slots. Although Beta radiation is easily detected, it is
difficult to measure accurately. Therefore, when a radioac­tive object is being searched for Beta radiation, the open
slots in the case should be positioned in such a way that
they are exposed to the object (see Figure 1).

If the unit shows a significantly higher click rate in this posi­tion, you can be reasonably certain the object is giving off
Beta radiation.

Now position the unit as shown in Figure 2. In this position,
where radiation cannot pass directly through the slots (Beta
radiation travels in straight lines for the most part) only
gamma and X-ray radiation from the object will be de­tected.

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THIS IS THE POSITION IN WHICH TO HOLD THE GEI­GER COUNTER TO TAKE READINGS. It is important to
understand this, for misleadingly high meter readings can
result from allowing Beta rays to be measured with the
gamma rays. The meter scale is calibrated for gamma ra­diation.

FIG. 2

READINGS

There are two Sper Scientific Radiation Monitor models:

840007 - 0.1 to 10mR/hr
840026 - 0 to 100mR/hr

All units are tested at the factory using gamma radiation.
The radioactive gamma source used in the factory is Ce­sium-137 that has been Beta shielded with .062" of Alumi­num, and measuring radioisotopes other than Cesium-137
introduces some error. The error caused by this is usually
very little. Note that in the case of X-rays, the unit is very
sensitive and subsequently meter readings should be di­vided by about 5.

The 840026 was calibrated. For how often you have to cali­brate your unit, check with your local NRC. However, you
must calibrate after each repair or change of G-M tube.
Since the 840026 radiation monitor has an oscillator, it can
be readily adjusted/calibrated by turning the screw on the
oscillator with a small screwdriver in the desired direction:
turning clockwise to decrease the reading; counter clock­wise to increase. This calibration should be done at a li­censed laboratory.

In addition to the analog meter, a special extended range
has been designed into the 840007 unit. At radiation levels
that are in excess of the meter scale, the unit will emit

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beeps, at a rate that increases as the radiation level in­creases. Although this range is not as accurate as the dis­played range, beeping will begin approximately at 15mR/hr.
A continuous beep occurs approximately at 20mR/hr.
These built-in ranges greatly simplify operation and allow
reasonably quick and accurate measurements to be made.

The meter is not intended to indicate levels below 0.1 mR/
hr., therefore, readings taken below this level should be
considered extremely crude. However, such low level
measurements can be made by simply counting the clicks
over a period of time, much like taking a person's pulse,
and expressing the result as clicks (or counts) per minute.

0.1 mR/hr, on the meter corresponds to about 330 counts

per minute.

INTERPRETING READINGS

Health physics, the field that pertains to radiation and its
effects on man, is very complex, and theories and con­clusions are constantly being updated as information be­comes available. Data from occupational exposure, animal
studies, and events like Hiroshima and Nagasaki have
fairly well established the maximum safe exposure limits for
man. Whether low level radiation causes cancer and birth
defects is still being debated. Delayed effect, which could
take years to develop, is difficult to study, and therefore,
there are no well-defined lower limits on ionizing radiation.
Two publications entitled "Hormesis with Ionizing Radia­tion," 1980 and "Radiation Hormesis," 1991 (CRC Press,
Boca Raton) present over one thousand examples of statis­tically valid data showing no physiological harm in verte­brates from whole body exposures to low dose radiation
(<20mGy/y).

As previously mentioned in the section on operation, the
units mR/hr (milli-Roentgen per hour, or 1/1000th of a Ro­entgen per hour) pertain only to gamma radiation. Often
other units of measurement similar to mR/hr are used. The
term "REM" (Roentgen Equivalent Man) includes the af­fects of beta, alpha and neutron radiation. Measurement in
REMs is more complete as radiation affects man, but such
measurements are a complicated combination of many
measurements each made with specialized detectors.

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It is important to note that the field intensity from a radioac­tive object decreases very quickly with distance.

If the object is very small, increasing the distance from the
object by a factor of two decreases the radiation level by a
factor of four. This is called a square law situation, which
demonstrates the dependence of proximity on dose for
small radioactive sources. Larger sources, such as a large
deposit of radioactive minerals, will show much less of this
effect. In trying to estimate the danger of radioactive mate­rials, it is important to take into account many aspects of
the situation. For instance, the radiation level at the face of
a radium-dial watch may be 3mR/hr, but the measurement
taken from the back of the watch may be 0.3mR/hr.

Another interesting point concerns the energy of the radia­tion. Geiger Counters will register one click whenever they
detect a ray or particle of radiation hitting them. These tiny
high speed bundles of energy are like short bursts of light.
Some are extremely energetic, while others are not. Geiger
Counters cannot determine the energy of the impinging ray,
they only detect its presence. Sper Scientific models
840007 and 840026, detect Beta and gamma radiation
starting at approximately 30KeV and up to 1.5 MeV.

The opposite is the case for cosmic rays, which have enor­mous energy — some millions of times more energetic than
anything found here on earth. The compensation figure for
radiation of this type is difficult to estimate, due to the ex­treme range of energies that have been measured.

RADIATION — WHAT IS IT?

Nuclear physics is a very complex field, however, the basic
principles can be simply explained.

All matter is composed of atoms. Atoms alone and bonded
together in molecules form all the things around us, includ­ing ourselves. These atomic units are extremely small; so
small, in fact, that a single grain of table salt contains ap­proximately 1,000,000,000,000,000,000 atoms (this is not a
misprint). It is impossible to see an atom, except with a so­phisticated electron microscope, so many of our present
day theories on the structure and composition of single at­oms are based largely on the study of radiation given off
from unstable (radioactive) substances.

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Atoms are composed of three basic particles: protons, neu­trons and electrons. Electrons are extremely light, nega­tively charged particles that exist as a cloud around the
center, or nucleus, of the atom. Sometimes the electrons
are said to occupy orbits around the nucleus. These elec­trons are attracted to the nucleus because of the positively
charged protons that, along with the neutrons, make up the
nucleus. Atoms bond together in molecules when one atom
gives up or shares an electron with another atom. Chemical
reactions utilize this bonding process.

In all atoms, the number of electrons (and therefore the
number of negative charges) equals the number of protons
(positive charges). The number of protons or electrons in
an atom determines the chemical nature of the atom, and
each element has its own unique number (example: hydro­gen = 1, helium - 2 etc.). The number of neutrons, how­ever, may not always be the same in every atom of a par­ticular element. Atoms of an element with different numbers
of neutrons are called isotopes. Every atom of a particular
element has the same atomic number, but different iso­topes of a given element have different atomic weights.

It is the variable number of neutrons in the nucleus of an
atom that leads to a process called nuclear decay that
causes radiation. When an atom has too many or too few
neutrons in its nucleus, it will have a tendency to rearrange
itself spontaneously into a new combination of particles that
are more stable. In this decay process, bundles of excess
energy are shot out of the nucleus in one of a number of
ways.

When the neutrons are excessive, a neutron can
convert itself to a proton and shoot out an electron
at very high speed, known as beta radiation.

A proton may be converted to a neutron to cause
an unusual particle called a positron to be ejected
from the nucleus.

In still another process, the nucleus, in a vain
atempt to stabilize itself, kicks out two protons and
two neutrons all together as one particle, called an
alpha particle.

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The energy released in each decay can be enormous. This
decay process is utilized in atomic reactors and bombs.
When certain very heavy isotopes of uranium or plutonium
(or several other isotopes) decay, they may split apart. This
process is called fission. In fission, the entire nucleus splits
apart, causing two new atoms and releasing a very large
amount of energy. This process is not very predictable, for
the nucleus can split in many ways, yielding a wide variety
of new atoms and even some free neutrons. The free neu­trons, when released, can be absorbed by other fuel atoms,
causing them, in turn, to fission -- leading to a continuous
or (if not controlled) explosive chain reaction. Due to the
wide range of new atoms produced in the fission process,
many of the daughter products are not stable and will, in
turn, decay themselves, leading to hazardous nuclear
waste and fallout.

In all of the above processes, another kind of radiation,
gamma, is almost always released. Unlike the particles pre­viously mentioned, gamma radiation consists of tiny, dis­crete bundles of energy called quanta. Light, X-rays and
gamma rays can all be described as quanta, the difference
being the total energy packed into each bundle.

In nuclear decay some energy in the unstable nucleus is
dissipated to its surroundings in the form of heat and radia­tion in the instant that it decays. The nucleus may remain in
its unstable state for billions of years, and then suddenly
decay spontaneously. The time required for half of the at­oms of a particular isotope to decay is called the half-life of
that isotope. For an isotope with a half-life of 1 year, the
pure isotope substance would be only 50% pure after one
year, half of the original atoms having decayed into some
other substance. After another year, 25% of the original
material would remain, and so on. Natural radioactive ma­terials in our world are only those with very, very long half­lives. Uranium-238, for example, has a half-life of 4 billion
years, and exists today only because not enough time has
elapsed since its creation for it to decay away to negligible
levels. It is thought that the universe was created from a
huge mass of subatomic particles and energy — the Big
Bang Theory.

Of the elements and their isotopes that constitute our
planet, the vast majority are quite stable, the result of bil­lions of years of nuclear decay. The amount of radiation

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given off from natural radioactive minerals in the earth's
crust is a major constituent of background radiation. For the
most part, it is quite low, due to the long time required for
the remaining radioisotopes to decay. In atomic reactions
(either natural or forced by man) the decay process is sped
up by the effect of neutrons given off in the fission process
interacting with more unstable isotopes to cause immediate
decay. While this allows the energy of the isotope to be
harvested in a conveniently short time, the unstable decay
products produced generally have short half-lives, on the
order of seconds to centuries, and are very radioactive. As
a result of this process, considerable larger quantities of
short half-life (high decay rate) isotopes become a part of
the world we live in. This is the basis for the controversy
and concerns on the subject of nuclear power generation,
waste disposal, and nuclear weapons.

INTERACTION OF RADIATION WITH MATTER

The particles and photons that result from nuclear decay
carry most of the energy released from the original unsta­ble nucleus. The value of this energy is expressed in elec­tron Volts, or eV. The energy of beta and alpha rays is in­vested in the particles' speed. A typical beta particle from
Cesium-137 has an energy of about 500,000 eV, and a
speed that approaches that of light. Beta energies can
cover a wide range, and many radioisotopes are known to
emit betas at energies in excess of 10 million eV. The
penetration range of typical beta particles is only a few mil­limeters in human skin.

Alpha particles have even shorter penetration ranges than
beta particles. Typical alpha energies are on the order of 5
million eV, with ranges so short that they are extremely dif­ficult to measure. Alphas are stopped by a ~nin sheet of
paper, and in air only travel a few inches at most before
coming to a stop. Therefore, alpha particles cannot be de­tected without being in close contact with the source, and
even then only the alphas coming from the surface of the
source can be detected. Alphas generated within the
source are absorbed before reaching the surface. Due to
short range, alpha particles are not a serious health hazard
unless they are emitted from within the body when their
high energy, in close contact with sensitive living tissue, is
an extreme hazard. Fortunately, almost all alpha-emitting
substances also emit gamma rays, allowing for their detec­tion.

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Neutrons, having no net charge, do not interact with matter
as easily as other particles, and can drift through great
thickness of material without incident. A free neutron, drift­ing through space, will decay in an average of 11.7 min­utes, yielding a proton and an electron (beta ray). The neu­tron can also combine with the nucleus of an atom, if its
path carries it close enough. When a neutron is absorbed
into a nucleus, it is saved from its ultimate fate (decay), but
may render the nucleus unstable. This absorption process
is used in medicine and industry, to create radioactive ele­ments from non-radioactive ones. Detecting neutrons is
specialized and beyond the scope of typical Geiger count­ers, but most possible neutron sources also emit gamma
and beta radiation, affording detection of the source.

The highly energetic X-ray and gamma rays lose their en­ergy as they penetrate matter. X-rays have an energy of up
to about 200,000 eV, compared to gamma radiation which
can be as energetic as several million eV. One million eV
gamma radiation can penetrate an inch of steel. Gamma
and X-ray radiation are by far the most penetrating of all
common types, and are only effectively absorbed by large
amounts of heavy, dense material of high atomic number,
such as lead.

SPECIFICATIONS

Calibration

model

840007 Gamma* 0~10 mR/hr +20% 30 KeV ~

840026 Gamma* 0~100 mR/hr +15% 30KeV ~

Radiation

Range

Typical

Accuracy

Min/Max

Detection

Energy

1.5 MeV

1.SMeV

*(Cesium 137)
1mR/hr=10µS/hr

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LIMITED WARRANTY

The 840007 and 840026 Geiger counters are warranted for
5 years on electronics and 1 year for G-M tube from the
date of purchase. If a unit fails to function properly within
the warranty period, Sper Scientific will repair or replace
the unit, at its option. This warranty does not cover any
damage to the unit as a result of misuse, accident or repair
by unauthorized personnel. Sper Scientific reserves the
right to make such determination on the basis of factory
inspection. All products returned for service must be
shipped prepaid.

REPAIR CHARGES

Replacement of G-M tube ..................................$ 50.00

Replacement of circuit board .............................$ 80.00

At time of repair, the monitor is recalibrated at no additional
charge.

NOTICE

Sper Scientific believes the Geiger Counter to be accurate
within reasonable standards of acceptance, and includes
instructions that, if followed, will yield accurate measure­ments. Manufacturer assumes no liability for damages,
consequential or otherwise that may arise from the use of
the Geiger counter by any person, under any circum­stances. This Geiger counter is sensitive to gamma, beta
and X-ray radiation, but not necessarily to extremely low
energy forms, or alpha, neutron or microwave radiation. Do
not open Geiger counter or otherwise tamper with or at­tempt to service it.

SPER SCIENTIFIC LTD

7720 East Redfield, Suite #7

Scottsdale, AZ 85260, USA

[phone]

sperscientific.com

[e-mail]

Returned unit must be accompanied by a description of the
problem and your return address. Please register your
product online or return your warranty card within ten (10)
days of purchase.

Rev 3/22/06

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