ML20076M862

Working Safely with Nuclear Gauges

ML20076M862
Person / Time
Issue date:	03/26/1991
From:	NRC
To:
References
NUREG-BR-0133, NUREG-BR-0133-R01, NUREG-BR-133, NUREG-BR-133-R1, NUDOCS 9103260067
Download: ML20076M862 (28)

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TABLE OF CONTENTS i

I Page grec$wnt State [.

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2. WilAT IS RADIATION 7.

3 2.1 Radiation is All Around Us.

3 2.2 How lonizing Radiatio _n Oecurs 5

2.3 Radi t.o from A to X.

7 2.4 Usin, f diat'm Saiely..

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3. NUCLEAR OAUGES.,.......

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3.1 Fixed Gauges 9

3.2 Portable Gauges.......

11 3.3 The Strength of the Source..

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4. ARE NUCLEAR O AUGES SAFE 7......

13 4.1 Principles of Radstion Protection......

15 4.2 Keeping Track of Your Radiation Dose....... 15 4.3 Under the Limit..

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4 4 Registration, Licensing, inspection, and Testing 18 l

5. PROPER USE OF NUCLEAR OAUGES......... 18

6. EMERGENCY PROCEDURES..........

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S 7, TRANSPORTATION 23 Ot.,OSSAL'.' OF TERMS.

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1. INTRODUCTION This booklet is the result of a cooperative.cffort be ween the Office of Governmental and Public Affairs and the Office of Nuclear ait '.erial Safety and Safeguards, both on the U,5.

Nucleer lu alatory Commission (NRC). This document was largely. adapted from the Atomic Energy Control floard of Canada publication " Working Safely with Nuclear Gauges."

This publication contains guidelines on the proper handling and

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. use of fixed and portable nuclear gauges, and providea

. background information about radiation for people who use and :

work around this equipment, i, is intenled to provide information to gauge licensees for use in their user training programs.

Information may be added or deleted to fit their specific train-Ing programs as needed Much of this information, particularly that on radiation, is not i

s usually found in the standard operating manuals for nuclear.

I gauges.. As a tesult, you may be unsure about the possible dangers from radiation, and uneasy about using or working near

- gauges that contain a radioactive source, After readirig this booklet, you should be able to work confidently and safely arourw nuclear gauges, t

Remember that this booklet is meant only as a general guide,

' For step by step instructions and complete regulations, it is ber 3-

- to check your operating manual and the license that NRC or W.M0li$hNIM the Agreement State issued you for the specific gauge you are

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using, L

1.1 NRC and the Agreement States

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- NRC is the Federal agency iesponsible for emuring the safety f 2

J of people who work with radioactive material and the security

- of certain radicar.tive materials. To controlihe risks associated

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with the use of nuclear energy, NRC sc ts strict health and safety -.

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- Natural radiation -

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. Cosmic rays: 30 millitem 6,000 miles Jetflight: 3 millirem

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Total dosehr:100 millire.n Total doselyr:

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4 standards for nuclear equipment, defit.cs allowable limits for radiation exposure, and frequently conducts inspections of nuclear products arid facilities.

As of March 1989, NRC has entered into agreements with 29 states that give them authority to regulate rahoactive materials ll used or possessed within their borders. Such states are called Agrecraene c'ates. The regulator of radmetive materials in your jurisdiction may be either the NRC or an Agreement State arul, hereafter, is simply referred to as the Agency.

For nuire information at ut NRC, please plume (301) 492 7000 or write to: Office of Governmental and Public Affairs, U.S.

Nuclear Regulatory Commission, Washington, DC 20555 Ques-tions about gauge licensing and regulation should te directed i

to the Agency, Specific questions or comments about this txxAlet l

shoukt be directed to Mr. Steven Baggett t. the above address.

2. WHAT IS RADIATION?

To understand nuclear gauges, you must first urmierstand some basic facts about radiation, its origins, and les p>ssible effects.

2.1 Fisdistion is All Around Us Quite sirnply, radiation is a form of energy. Radiation comes f

from atoms, the tellding blocks of all testter, and is around us all the time.

M$hiiIIBMib Although many of us associate the woni "radiathm" with dargw, and illnesses su(h as cancer, radiation is not necessarily harm.

ful. Burning a log, for example, gives off radiant energy (radia-tion) in the form of both heat and light. And wien you lie in the sun too long, you can get a sunbunt. which is a mild radia-tion burn. However, the har.ards that come to mind when you think of radiation are nest often associated with what is called

" ionizing radiation "

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tion. This radioactive decay continues until the atom changes

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to a stable form.

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s We are all exlmed to ionizing radiation every day. In fact -

natural backgmund radiation-from soll and nels, from the fm!

we eat, from the touses we live in, from cosmic rays, even from out own bodics-contributes to atout two-thirds of our annual radiation exiosure. Although we canrot control natural

. background radiation, the amount we receive each year is so low that it presents little health hazards.

I We are also exposed to several man made sources of ionizing i idiation through our daily activities. Time include wraching o'.

television, arr4ing, having s1 X ray at your doct#s or dernist's office, or wearing certa er jnous dial watches. Other activities Increase our exposure te r%ral radstion. For example, airplane s

flights expose us to increased cosmic rays. However, we can control the amount of radiation we receive from these sources by simply limiting the related activities.

lE The chart on page 2 shows how much ionizing radiation we normally receive from varkms namral and mairmade sources, Doses are given in millirem, whkh is the traditional unit for j

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- measuring the amount of radiatiori the body absorbsa m

2.2 How lor.laing Radiation (w: curs 3

Most ionizing radiation results wh ra the structure of an atom's electrons, neutrons and protom b vak down. This can happen.-

when some form of ionizing redigion collides with a normal:

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- atom, or when an unstable atom (antled a radioisotope) decays '

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- or breaks down on its own. Radioisotopes release energy in the

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- form ofionizing radiation repeateSy over a specific length of

' time, until all the atoms become stable

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. flash bulb on a camera going off. When a bulb is triggered,

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. energy is released as a flash of light, The bulb then changes t

its form to a spent bulb and is no longer capable of flashing.:

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Neutron I l h-l 7he nations types ofionizing radiation have diferent penetrating powers. This portrays the ability of diferent forms ofionizing radiation to penetrate,> aper, the human bmly, umi, and concrete.

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The release of ionizing radiation is similar, except that there is no visible flash. A decaying atom gives off energy as radia-tior* and then changes into a new form, llowever,.mlike the flash bulb, you cannot see radiation and cannot tell that the new i

,3 form of atom is still decaying and capable of giving off radio-active energy. A radioisotope may undergo several changes and release radiation over a long period of time before changing to a stable form.

2.3 Radiation from A to X llere are the main types of ionizing radiation:

• Alp's radb:N : large atomic particles that both namtal

,ihilh W # @ p siig g g g g g M M g g i elements ano some man-made substances emit-alpha radia-tion has little external penetrating power, but can be harmful if you breathe or swallow radioactive elements.

• Beta radiation: fast moving atomic particles with little penetrating power-beta radiation is frequently found inside a medical or research environment.

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• Ganuna radiation: electromagnetic waves resulting from j

. radioactive decay-this type of. radiation has greater punctrating power than medical X rays, and is often used in

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• Cosmic radiation: these are highly energetic atomic particles i

that originate from the sun atu! stars and penetrate the carth's atmosphere.

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• Neutron radiation: penetrating atomic particles that result from collisions between cosmic rays and atotr.4 in the I

atmosphere, and from some specialized man-made sources-this type of radiation is often used in portable nuclear gauges,

• X-rays macidne generated electromagnetic waves that can penettre,e the human body-this type of radiation is used -

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fued gauges are widely u. sed today infactories and prwessing environments to eruure quahty control Radiation is released by a shutter being apened; the radiaritn passes through the

• +M$t%%' 1Ruf%MMEl.w(Ikin material; and then a detector mounted opposite the source measures it. The amount of radiation detected hulicates the thickness or demity of the material

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2.4 -Using Radiation Safely j

All types of ionizing radiation can be harmful. Long term ex-f posure to a small source of constant radiation, or short-term '

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- exposure to a large amount of radiation can cause damage to our cellular structure or tissue. However, these risks can be minimized and controlled, allowing radioactive sources to be used safely for many productive purposes. The following see-l -:

i tion describes such a purpose, the use of radiation in nuclear -

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3. NUCLEAR GAUGES.

.y Today, many industries tne equipment such as nuclear measur-ing gauges that incorporate a radioactive source. %ese nuclear r

- gauges provide an inexpensive, yet highly reliable and accurate ;

method of measuring the thickness, density, or make up of a ;

O wide variety of material or surfaces.' There are two types of' nuclear gauges, fixed and portable.

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3.1 - Fixed Gauges.

?r Fixed gauges are'most often used in factories as a way of.

monitoring a pro'uction process and ensuring quality control.

In many pra-a, either products cannot be effectively checked I

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'these fixed gauges consist of a radioective nource that is twused

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. within a source holder and placed at a crucial point in the pro 7 l-g i-cess. When the source holder's shutter is opened, an invisible ;

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beam of radiation is directed at the material being processed.,

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. The use ofponable gauges is widesprea in in ustries suc as

.- agriculture and construction. In the illustration on the lep, the.

gamma source is placed underneath the surface of the ground

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thnwgh a tube. Radiation is then transmirsed directly to the deres.

k-tor on the bottom of the gauge, allowing accurate enensurements ;

ofconnpaction. On the right, the neutron source remains above

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moisture consent.

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A A detector mounted opposite the source measures the radiation that passes through the material. A readout either on the gauge or on a connected computer terminal registers the required in-formation; for example, the thich ness of a product as it passes l

between the source and the detector, or the level of liquid in l

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a bottle as it is being filled The passage of radiation does not cause any detectable change in the nuterial, and the material itself in no way becomes radioactive.

Fixed gauges are commonly used in all types of processing environments, from mills to breweries. In a paper mill, fixed gauges can measure the thickness of a sheet of paper as it leaves the presses. In a brewery, a fixed gauge makes sure that each i

bottle contains the right amount of beer. Whatever the applica-1 tion, these gauges ensure quality control in a process.

3.2 Portable Gauges Portable gauges are used in industries such as agriculture, con-

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struction, and civil engineering to measure things like the moisture in soil, and the density of asphalt in a paving mix, There are two basic methods of measuring material with port-able gauges, backscatter and direct transmission.

Direct transmission is considered the more precise of the two, as it offers less error in measuring composition and compen-sates for surface roughness. To measure soil density, for ft4ii$it example, the source is placed in a tube and insetted beneath the.

i surface through a punched acccu hole. Radiation is then transmitted from the source to a detector on the base of the gauge.

The density of the soil is deterroined by the radiation level at the detector, j

i The backscatter method climinates the need for an access hole by allowing both the source and detectnr to remain on the sur.

face. Radiation is directed beneath the surface, and some radia-i tion is reficcted, or scattered, back to the gauge detector by the

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i All nuclear gauges use a radisactwe source that is placed in QfJ.:7;f' :% Q JNkt hi(3$;tatttQp a specialdouble nyn!e. Thitavsnit, which can be as small t

as the eraser M the tip of a y. -Q orcs large as the tube inside a roll ofpaper towels, is then kum*J hito the gauge's source housing, which shields the radiwian mwdpom the source.

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surface material. This method can be less accurate than direct transmission, due to the large scattering angle and shallow depth of measurement. It is also insensitive to density variations beyond a depth of two to three inches, llowever, the backscatter method is quicker ark) easier than direct transnussion, and is useful when measuring uniform material such as asphalt paving.

3.3 The Strength of the Source Each nuclear gauge uses one or two small radioactive sources containing americium-241, cesium 137, americium-241/ beryl-lium, krypton-85, radium-226, or cobalt-60. The source's strength is measured in terms of how much radioactive energy it gives off. Although these sources are physically quite small, they are often extremely powerful and highly radioactive.

Ilowever, it is the amount of radiation you absorb, not the strength of the source or the amount of radiation it can emit, that can pose a danger to your health.

You are protected from receiving excess radiation by the umrce shielding, by proper h:ndling techniques, and by the fact that the Agency performs a safety evaluation of all nuclear gauges in the United States to ensure that, under proper use, they will pose no radiation hazard. "Ihe following section outlines the many ways in which the possible hazards associated with nuclear gauges are minimized.

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4. ARE NUCLEAR GAUGES SAFE 7 Nuclear gauges are tools like a power saw or a welding torch that may be hazanicus unless proixt safety precautions are taken.

• kA'*,bbMb,s But because the potential harm from radiation is not as obvious as the dangers from a sharp blade or a flame, the safety precau-tions are not as obvious either. By following a few simple rules, I

you can be assured that working with or around nuclear gauges l

will pose no threat to your haalth at4 safety.

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' The three elements ofradiation protection are time, distance,

- _ and shielding. The less time you spend in the area cfradiation, -

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the less ofa radiation dose you will recein. Likewhe, the efects -

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4.1 Principles of Radiation Protection Three factors come into play when protecting yourself from the effects of radiation: time, distance, and shielding.

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• Time: the less tirne a person rernains in the area of radiation, the less of a radiation dose that person will receive.

• Distance: the intensity of radiation and its effects fall off sharply as you move funher away from the radioactive source.

For example, by moving twice as far away from a radioac-tive source, you are exposed to one-quarter the amount of radiation; moving three times as far away means one ninth the exposure, and so on.

• Shiebings potective material placed between you and the sor.rce reduces the level of radiation passing through, and thus the amount to which you will be exposed. in nuclear gauges, this protection is provided by the source housing, 4,2 Keeping Track of Your Radiation Dose By following the time, datance, and shielding principles of radia-l tion protection, you can minimize the amount of radiation you i

absorb. You can also monitor that radiation done with special

- measuring devices.-

Workers who use portable gauges, or those who conw into I;

regular contact with fixed gauges, can keep track of how much d

, radiation they receive by using a personnel measuring device called a dosimeter. Due to the small anw.mt of radiation that N M' i, workers normally receive, these devices are not usually tequired, but they are available. The three most commonly used types of -

dosimeters tre direct readmg dosimeters (DRDs) and film badges -

l or thermolumiacscent dosimeters (TLDs). These devices are -

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l These devices measure the amount of nutiation you'obsorb. The DRD provides an immediate Indication of your exposure.

.whereas thefim or ll.D badge measures yrmr accumulated '

dosage, At a minimum,fim badges should be exchanged at in.-

t-tervals not to e.tceed one numth and 11.Os at intervals not to -

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The DRD allows you periodically to check the amount of radia.

tion you are receiving at any given moment. A quartz fiber within

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and provides an indication of your exposure. g r.long a scale A film badge contains film that is darkened by radiation. The radiation dose can be determined by reading how dark the developed film is. TLD's contain unall chips of material that

. absorb radiation in a measurable form. You are required to wear -

a film badge or a TLD if stated in the license, or if you must handle the source when servicing your gauge. These devices

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of time. Never leave any dosimeter behind when you are away

. from the ' gauge as it will continue to absorb radiation, making

it impossible to tell how much radiation you have actually;

-received.

4.3 ' nder the Limit U

Although you have a responsibility to minimize the ' amount of i-radiation you absorb and, if required by the license, to monitor g

- your radiation dose, the Agency also has a role to play in en-

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suring your safety. First, the Agency regulates the use of nuclear

' devices to ensure that you are not. exposed to radi.~ ion 2

unnecessarily. Second, the Agency regularly inspects licensees

-:to ensure compliance with the regulations. Third, the Agency:

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I-u sets limits on the amount of radiation to which you may be exposed.

. Although a certain amount of radiation is always present when J.$ ~

nuclear devices are being used, people who work with or around

- i nuclear gauges are limited to no more than 1.25 rem (1250 -

a millitems) of radiation a calendar quarter -

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,In practice, you would likely be exposed to much less radiation

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-than 1.25 rem per calendar quarter. The average annual

. measurable exposure of gauge users is about 100 millitems,'

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i which is vil within the acceptable safety levels set by the Agency.

4.4 Registration, Licensing, inspection, and Testing i

The operation of the gauges you use, or are exposed to, must comply with Agency regulations. All gauges must be registered with the Agency and approved for use before being put into s

operation. Once a gauge is approved, the Agency issues a license a

to the co npany who will be using it.

Once a gauge is in place and being used, tests must be performed regularly to ensure that the radioactive source is secure within its capsule and is not leaking out (called a leak test). Your company or organizata must arrange for an approved organiza-

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tion to perform these leak tests within the required interval. If the source is not leaking, your company will receive a docu-ment to : hat effect. Note that a small amount of radiation always penetrates the gauge housing and can be detected in a radiation

.I survey even if the source capsule is intact. This low level radia-tion poses no measurable health risk. The Agency will nornudly conduct a compliance inspection once every two years to see if the tests have been performed on schedule, and to ensure that other license conditions and Agency regulations are being followed.

Of course, in order to ensure complete safer / with nuclear gauges, you must, as with any ype of equiptwnt, follow the

?h YrYMM*3*'bb@M4/8N#1 operating rules. The following section provides guidelines on

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the proper handling and maintenance of nuclear gauges.

5. PROPER USE OF NUCLEAR GAUGES Working with and around nuclear gauges is no different than workiri, with any other type of industrial equipment. Certain rules must be adhered to and procedures followed to ensure safe use. Always carefully follow the oprating procedures provided k

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by the rnanufacturer llowevc',if the manufacturer's instruc-I tions differ frtun the Agerry's, ownply with Agency rep 'atka The following is a ut of gercral ukichnen on using, servicing, E

storing and tramixxting tised and portable nuclear gauges.

4 GaugeA Guidelines lhed Portable Before You Start Never use or manipulate a gauge j

wit %ut proper training, knowledge of the istruction inanual, ard authorization.

Read the corditions of the license.

l'ost a copy of the license in a common area where all workers can we it.

Keep a copy of the lica:se in the p.uge storage ca.w.

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Gauges l

Guidelines I'lted Portable Ensure that radiation warning signs are prominently posted in any area where nuclear gauges are being used.

Advise other workers that a portable nuclear gauge is being used.

Make sure that the gauge is clearly and e

durably labelled with the radiation l

'I warning symbol, and with the name and telephone number of the person to con.

tact in case of problems.

l Maintenance and Service I

Only the supplier of the gauge, or a j

. person authorized by the Agency.

t should attempt to repair the source, I

source holder, or shutter.

l Always lock the shutter in the "off" position until maintenance is completed.

e Only remove the source rod for servicing if the Agency has given authorization in the license.

eq Meg 19259 9 N % W '12 ( MITiW Q G@ 9tM $ m Avo d any physical contact with, or direc* cxposure to the source when performing any maintenance.

Clean the gauge orve or twice a week to prevent dirt from getting near the shutter.

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Gauges Guidelines Fixed Portable 1y s

if necessary when using a nuclear gauge in the field, clean the area around the shutter throughout the day.

Make sure the gauge is leak tested every six months, or as specified by the manufacturer's instructions, but not exceeding intervals of three years, i

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• M LAN Storage llefore storing the gauge, make sure the source is in the "saft." position.

Lock the source and shutter in place.

Never modify or change A: source holder, shielding or safety interlocks g

without Agency approval.

Store the gauge in a locked container or area.

identify the container in case the gauge is lost, damaged, or misplaced.

Lock the area where the gauge is being

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stored Post a radiation warning siga outside the storage area.

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- Flaed Portable Transportation and Disposal When sending gauges anywhere, make ~

proper arrar.gements for receipt of the package at the other end.

When taking a gauge to and from a job -

-site, place it in its storage container and

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keep it in an unoccupied part of the

_ vehicle, such as the locked trunk or i

secure it to an integral part of the i

vehicle, e

3 Lock the vehicle if the gauge is in it.

- When sending a gauge to the supplier, package it according to the Federal a

- regulations on the transport and packag-ing of radioactive materials. Label the y--

package to indicate its contents and affix a radiation warning label. (Further information on packaging can be ob-

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tained by contacting the Agency and the U.S. Department of Transportation.)

L For disposal, return gauges to the sup-plier or to a waste disposal organization.

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l 6.- EMERGENCY PROCEDURES Your company or organization rnust have a set of emergency-g procedures and a plan of action in case of an accident or in the

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event of damage to the gauge, if you are uncertain alwt what l

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to do should a malfunction, accident.or damage occur, take the

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followir t steps:

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• Cease work immediately.

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• If the gauEe has been partially damaged or destroyed, keep f-!

people at least 20 feet away until the source is replaced or shielded, or amtll radiation levels are known.

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.* Have led tests performed after any incident that may reruit

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t-in source damage

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• In case of an accident or fire, do not use the gauge until any

- danger from or damage to the source is asscased.

• Infottn the Agency within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of any theft, accident or

-incident involving the gauge.

Nuclear gauges present no major health dangers if basic precau, tions are taker: sud comnen acnse used By following proper.

. procedures and the principlec of radiation protection, and by.

helping rAhers do likewise, you can feel comfortable and assured

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that your workplace is a safe one.

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7. TRANSPORTATION-Safety in the transportation of radioacth 3 materiala depends on j{!$cyy ;

. proper packaging and on the effic at manner in which the packages are handled, stored ai cransported.' Nuclear gaugea are typically transported in Type "A packagess

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Type "A" packages normally contain 'elatively small quantities l

of radioactive materials, and therefore, re requved to withstand only the normal rigors of transportation. To be in compliance with the regula: ions, such packages must be able to withstand drop, penetration, compression and vibration tests, as well as exposure to extreme climatic conditions that are encountered in normal transportation. Each shipper is required to rnaintain on file the results of the paciage testing.

y Licertsees who transport gauges to and from temporary job sites in licensee or private vehicles arc shippers acting as private car-riers and, as such, must comply with DOT reFulations govern-ing both shippers and carriers (49 CFR 170-178).

Listed below are common violations which are typical of a licensee who acts as both a user and a shipper / carrier of radioac-tive materials.

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• Shipping papers must be carried in the vehicle. Such papers must contain certain information and be stored within easy reach of the driver of the vehicle.

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• The shipper must label and mark each package (case) used i

for transporting the gauge.

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• Each shipper must maintain on file the ruults of tests con-ducted on the transport package and the sealed sources con-phl4@y5NikNCl#(ds#%tldWW$%W!!

tained in the gauges.

• The package (gauge by itself or within a case) must be blocked i

and braced to prevent ravement of the package within the vehicle.

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GLOSSARY OF TERMS i

Agreement State: a State that has signed an agreement with l

the U.S. Nuclear Rerulatory Commiaon, allowing the Stau to regulate the use of radioactive materials.

U.S. Nuclear Regulatory Cotumissioni the regulatory body responsible for ensuring the safety and security of nuclear prw ducts and facilities.

Ilackground radiation: naturally e: curring ra6ation to which we are exposed all the tirne.

Compliance inspection: an inspection perforud by the Agency to ensure that leak tests have been performed ami that license I

conditions are being followed.

Ihne: the radiation absorbed -by the txxty.

Doshnetert a personal rneasuring device used to monitor the amount of radiation absorbed.

lonizing radiation: the result of the breakdown, or decay, of an atom's structure, Leak tests: tests performed on nucicar pues w.

.sure tint the source,apsule is intact. Typical intervah ate at 6 nwntL and at 3 years.

@$$k'YN hian made radiation: the radioactive t ubs:ances, or sources l

of radiation, created by man, e.g., a medical X-ray.

Radioisotope: a radjoactive element or form of element, either man-made or natura4y-occurring.

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1 Rem: the tradit onal unit for measuring a radiation dose. One

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i rem equals 0.01 sievert.

s Scaled source: a radioactive element that is encased in a pro.

tective capsule and is used in equipment such as a fixed or por-table nuclear gauge.

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