B.P. Smith, RE. Lee

A> AECL EACL

AECL-11567 CA9700302

A Description of 60Co Gamma Irradiation Facilities in theRadiation Biology and Health Physics Branch

Description des installations d'irradiation gamma au 60Code Radiobiologie et Radioprotection

B.P. Smith, RE. Lee

June 1996 juin

VOL 2 8 Hi 1 9

AECL

A DESCRIPTION OF 60Co GAMMA IRRADIATION FACILITIES IN THERADIATION BIOLOGY AND HEALTH PHYSICS BRANCH

by

B.P. Smith and P.E. Lee

Radiation Biology and Health Physics BranchChalk River Laboratories

Chalk River, Ontario KOJ 1J01996 June

AECL-11567

EACL

DESCRIPTION DES INSTALLATIONS D'IRRADIATION GAMMA AU "CODE RADIOBIOLOGIE ET RADIOPROTECTION

par

B.P. Smith et P.E. Lee

RESUME

Le service Radiobiologie et Radioprotection assure la gestion de trois installations d'irradiation au *°Co(Gammabeam 150C, Gammacell 200 et Gammacell 220). Ces installations conviennent a des applicationsdiverses en raison de la vaste plage de doses d'irradiation possibles. Le present rapport decrit lescaracteristiques des installations, les mesures dosimetriques et les procedures d'exploitation.

Radiobiologie et RadioprotectionLaboratoires de Chalk River

Chalk River (Ontario) KOJ 1J01996 Juin

AECL-11567

AECL

A DESCRIPTION OF 60Co GAMMA IRRADIATION FACILITIES IN THERADIATION BIOLOGY AND HEALTH PHYSICS BRANCH

by

B.P. Smith and P.E. Lee

ABSTRACT

The Radiation Biology and Health Physics Branch manages three 60Co irradiation facilities, to(Gammabeam 150C, Gammacell 200 and Gammacell 220) provide a range of dose rates suitablefor a variety of applications. This report describes the physical characteristics of the facilities, adescription of the dosimetry and operating procedures.

Radiation Biology and Health Physics BranchChalk River Laboratories

Chalk River, Ontario KOJ 1J01996 June

AECL-11567

CONTENTS

Page

1 INTRODUCTION 1

2. BASIC FACILITIES 1

2.1 Physical Layout 12.2 Radiation Sources 1

2.2.1 Gammabeam 150C 12.2.2 Gammacell 200 22.2.3 Gammacell 220 2

2.3 Dosimetry 22333444

2.4 Cobalt-60 Gamma Decay Calculations 52.4.1 Gammabeam 15 0C 5

2.4.2 Gammacell "Dead-Time" Dose Calculations 5

3. RADIATION DOSE CONVERSIONS 6

4. REFERENCES 7

ACKNOWLEDGMENTS 7

APPENDIX A Operating Procedures 22

APPENDIX B Decay Charts 30

continued....

Dosimetry2.32.32.32.3

2.3

.1

.2

.3

.4

.52.3.6

HistoricalKeithley Therapy DosimeterIonization ChambersGammabeam 150C Dosimetry2.3.4.1 Dose Rate Summary (for 1994 September 12)Gammabeam Dose/Distance CalculationGammacell 200/220 Dosimetry

II

CONTENTS (concluded)Page

LIST OF FIGURES

1. Gammabeam 150C 8

2. Gammacell 200 9

3. Gammacell 220 10

4. Gammacell 150C Radiation Field (50 cm) 11

5. Gammacell 150C Radiation Field Cross Section (50 cm) 12

6. Gammabeam 15 0C Radiation Field (392 cm) 13

7. Gammabeam 150C Radiation Field Cross Section (392 cm) 14

8. Gammabeam 150C Radiation Field (989.5 cm) 15

9. Gammabeam 150C Radiation Field Cross Section (989.5 cm) 16

9a. Gammacell 200 Isodose Curves 17

9b. Gammacell 220 Radiation Field 18

10a. Gammacell 220 Isodose Curves 19

10b. Gammacell 220 Isodose Curves 20

Al Gammabeam 150C Control Panel 25

LIST OF TABLES

1. Cobalt-60 Decay Table 21

B1. Cobalt-60 Decay Chart for Gammabeam 150c 31

B2. Cobalt-60 Decay Chart for Gammacell 200 32

B3. Cobalt-60 Decay Chart for Gammacell 220 33

1 INTRODUCTION

The 60Co gamma irradiation facilities, managed by the Radiation Biology and Health Physics Branchat the Chalk River Laboratories (CRL), include a Gammabeam 150C, Gammacell 200 and aGammacell 220. These facilities, which were all manufactured by Atomic Energy of Canada Limited,Commercial Products (now Nordion), provide a range of dose rates suitable for a variety ofapplications. Increasing internal and external demands for use of the facilities has prompted theacquisition of a dosimeter for routine dose rate calibrations. This document provides a physicaldescription of these facilities and the dosimetry and operational procedures used in these facilities.The Radiation Biology and Health Physics Branch has additional irradiation facilities including x-ray,neutron and 137CS sources are described elsewhere (Freedman et al. 1994).

2 BASIC FACILITIES

These facilities, in combination with experienced personnel, offer the opportunity to do a widevariety of radiation exposure applications. The Gammabeam 150C is currently located in building404B, with a planned move to the new Biological Research Facility (BRF). An addendum to thisreport will be attached describing the new facilities in the BRF after they become operational. TheGammacell 200 and 220 units are located in Building 513 A, Room 2 at CRL. Access to allirradiation facilities is restricted to trained personnel who must book the facility in advance, obtain akey from the current owner (Blake Smith) and return the key on sign-out.

21 Physical Layout

The Gammabeam 150C is housed in a shielded room and provides a beam of 60Co radiation(Figure 1) offering the advantage of a variable dose rate and target size. The Gammacells 200 and220 are self-contained irradiation sources (see Figures 2 and 3). The60Co radiation sources areshielded by a lead castle and are accessed by a movable irradiation chamber in the Gammacells.

2 2 Radiation Sources

2.2.1 Gammabeam 150C

The Gammabeam 150C is a 60Co irradiation facility designed for use in a shielded room (AECL1979). See Appendix A, Section 1 for an operating procedure. It is a basic panoramic unit equippedwith a beam port head (Figure 3) emitting a radiation beam (5.08 cm. by 2.85 cm) at the cylindricalsurface of the source. The beam is confined to 15° above, below and to either side of the beam. Thisunit was charged with 179 TBq (4.82 kCi) of 60Co in 1968 May. The source in the down position isshielded, whereas when the drawer is raised the source becomes fully exposed in the beam port.Source exposure time is controlled by an electronic timer designed at CRL. The Gammabeam roomhas a solenoid operated door interlock as a safety measure. This facility offers a variable dose ratedependent on the distance from the source (Table Bl).

2.2.2 Gammacell 200

The Gammacell 200 is a 60Co irradiation facility designed for use in an unshielded room (AECL1970). The unit consists of an annular-shaped source, a lead shield around the source, and a longcylindrical drawer, free to move vertically through the centre of the source. The unit was chargedwith 17.8 TBq (480 Ci) of 60Co in 1975 May. The drawer carries samples to be irradiated fromoutside the shield to inside the source. Irradiation of samples up to 8.9 cm in diameter and 13.9 cmin height can be undertaken with relative safety for operating personnel (< 5 mrad/hr on contact).An access tube in the drawer top allows liquid, gas, electrical or mechanical connections to thesample chamber. A CRL-designed digital electronic timer allows control from 0 to 999 in periods ofseconds, minutes or hours. (See Appendix A, Section 2 for the Operating Procedures). The doserate for 1996 June was 1.45 R/s (1 R = 2.58 x 10"4 C/kg)(Table B2).

2.2.3 Gammacell 220

The Gammacell 220 is also a 60Co irradiation facility designed for use in an unshielded room (AECL1978). The 220 unit is essentially identical in operation to the 200 (see above) but has greatershielding to accommodate 897 TBq (24.25 kCi) of 60Co, charged in 1980 January. The cylindricalsample chamber is 20.5 cm high and has a diameter of 15 cm with external access during irradiationvia a one-inch channel through the top of the drawer. A CRL-designed electronic timer allowscontrol of exposure time from 0 to 999 in periods of seconds, minutes or hours (See Appendix A,Section 3 for the Operating Procedures.). The dose rate for 1996 June was 4.091 kR/min. (TableB3).

2.3 Dosimetrv

Dosimetry is presently performed using ionization chambers of varying volumes connected to aKeithley Therapy Dosimeter. The instrument and ionization chambers are calibrated by theInstrument Calibration Section of the Radiation Biology and Health Physics Branch, against NationalResearch Council of Canada standards.

2.3.1 Historical

Prior to 1994, dosimetry of the facilities was based on calibrations using the Fricke method (Spinksand Wood 1964). This is a chemical method that involves the oxidation of an acid solution offerrous sulfate to the ferric salt, in the presence of oxygen and under the influence of radiation. Thisis performed under meticulously "clean" conditions and solutions are read on a spectrophotometer,comparing absorbance of irradiated and non-irradiated samples at 304 nm (the maximum absorbanceof the ferric ion). Calibration curves of dose versus time are constructed. This method was designedto measure higher doses (>40 Gy) but can be tailored for lower doses. In practice, the error isapproximately 10%.

2.3.2 Keithley Therapy Dosimeter

All dose measurements reported in this document were made using a Keithley Model 35040 TherapyDosimeter. This instrument provides automatic correction for air density (temperature andbarometric pressure) and ionization chamber volume. The instrument provides a bias voltage for thechamber through the connecting cable, which also returns the signal. See Appendix, Section 4, foran operating procedure. This is a reference grade instrument and is extremely stable, linear andmaintains zero drift. The instrument uses calibrated ion chambers to simultaneously measure anddisplay dose and dose rate in user-specified radiological units. Roentgens per minute, (R/min.) areused for most measurements. It also supplies a stable, user-programmable, electronic bias voltagefor ion chambers, which is continuously monitored. Calibration factors for ion chambers, pressuremeasurement units and bias voltage are input from an IBM PC compatible computer anddownloaded to the electrometer's EPROM where the values are stored. Additional factors such asdaily temperature and barometric pressures are entered at the front panel of the instrument.

2.3.3 Ionization Chambers

Exposures are measured using ionization chambers of varying volumes, depending on the requireddose range. The Farmer-type 0.6 cm3 chamber consists of a thin-walled, high-purity graphite thimbleand a pure aluminum electrode, supported by a thin-walled aluminum stem. This is connected to themeter by a length of low noise triaxial cable with a Bendix TNC triaxial plug. An electrical bias of300 Vdc is normally applied. The probe tip is protected by a 0.3 MV to 2 MV, vented, built-up cap.A Keithley Model 35040 Therapy Dosimeter with a New England Technologies 15 cm3 flat,

graphite ion chamber with a 5-mm Perspex window was used to measure intermediate doses. Thecalibration factor for the detector was 2.094 roentgens per nanocoulomb (R/nc), as establishedagainst a 35 cm3 ion chamber previously calibrated against a National Research Council of Canadastandard. Ionization chambers for lower ranges are also available.

2.3.4 Gammabeam 150C Dosimetry

The Gammabeam 150C fields were mapped at three distances corresponding to low, intermediateand high dose rates. See Figures 4 to 8 for details. In addition, cross sections at each distance weremeasured until a significant decrease dose energy was found at each side of an arbitrary midpoint.For the 50-cm measurement, a reading above and below the centre point was taken to give a verticalprofile of the beam. The resulting dose measurements were then plotted using a spreadsheetprogram and the respective graphs were plotted. Note that the dose will decrease as a function ofdistance from the midpoint. All exposures therefore should be calculated and performed at thecentre of the beam. See Appendix B for monthly dose decay charts from 1996 January to 1999December for the three radiation sources.

2.3.4.1 Dose Rate Summary (for 1994 September 12):

50cm-9.38R/min.392 cm-0.148 R/min.989.5 cm-0.027 R/min

2.3.5 Gammabeam Dose/Distance Calculation

When using the Gammabeam 150C, the option of using a given dose rate is available by selecting anappropriate exposure distance. Dose rates may also be calculated by using the inverse square law(e.g., when the distance from the source is doubled, the dose rate is reduced to one quarter).

Example: A dose rate of 9.38 R/min. measured at 50 cm from the source becomes(9.38/4) or 2.345 R/min. at 100 cm.

Example: To calculate the distance for a given dose rate, - for example. 2 R/min. proceed asfollows:

Dose rate is proportional to factor K/distance2

At 50 cm the dose rate is 9.38 R/min (measured), factor K is calculated to be

9.38 R/min = K/50 2

Therefore K = 23450

To deliver 2 R/min, the distance from source is calculated as

2 R/min = 23450 / distance2

distance = 723450/2 R/min = 108.3 cm

Therefore, the distance from source to deliver a dose rate of 2 R/min is 108.3 cm.

2.3.6 Gammacell 200/220 Dosimetry

The Gammacell 200 and 220 radiation fields were measured using a previously calibrated 0.6 cm3

graphite pencil-type ion chamber. The calibration factor for this detector was 5.024 roentgen pernanocoulomb. The gammacell measurements were made at three different heights (bottom, middleand top) of each chamber (Figures 9a and 10a). At each height, five measurements were made togive a cross section. See Appendix B for monthly dose decay charts for the three radiation sources.

Note that the fields within the irradiation chamber of the Gammacells follow isometric dose curves.(See Figures 9b and 10b) There is an increase in dose from the midpoint to any of the vertical wallsand a decrease in dose as you approach the top and bottom of the chamber. This is to due to the

geometry of the chamber in relation to the position of the sources. Again provision should be takento use the midpoint, whenever possible.

2 4 Cobalt-60 Gamma Decay Calculations

Cobalt-60 decays with a half life of 5.27 years (63.24 months). Therefore each month the dose rateis reduced by 1.096% resulting in the necessity of calculating the dose rate on a monthly basis. SeeAppendix B for monthly dose decay charts for the three radiation sources. This is done routinelyusing a decay rate table (Table 1). To calculate a current dose rate, the measured dose rate for agiven date (starting time) is multiplied by the decay factor for the current date, as read from thedecay table. These values are calculated from the equation:

i ^ 11/2Ji.now -ti.0

where

Activity^ Activity ^e1-1^where

tw = half-life of 60Co (63.24 months)= present time minus starting time (in months)

2.4.1 Gammabeam 15 0C

A measured dose rate for a starting time of 1994 September of 9.38 R/min. for the Gammabeam150C has decayed in 18 months (1996 March) by a factor of 0.8209, as read from the decay table(Table 1). Therefore, the 1996 March dose rate is (9.38 x 0.8209) or 7.700 R/min.

2.4.2 Gammacell "Dead-Time" Dose Calculations

For the two 60Co gammacells (the 200 and 220), the pencil sources are fixed. The irradiationchamber, containing sample materials, is lowered into the gamma field by a mechanical elevatorsystem. As the chamber moves down towards the exposed pencils at the "rest" position, the materialin the chamber gradually sees an increasing field. Therefore, the sample is being irradiated as it isbeing lowered into position. To account for this, the required exposure time must include the dead-time dose. (i.e. dose = dead-time dose + exposure dose for time 't') Both dead-time dose andexposure dose must be corrected for decay of the source. These values are given for the datesbetween 1996 January and 1999 December in tables B2 and B3.

Using the 1994 September Keithley data from Figures 4, 9 and 10, the dose rates for the next 5 yearshave been calculated. See Appendix B, (Bl, B2, B3).

3. RADIATION DOSE CONVERSIONS

The dosimetry provided by the Keithley Therapy Dosimeter is read in roentgens. However, someapplications require dose rates in water or tissue, expressed in rads or grays. Roentgens are definedas the exposure that generates one electrostatic unit of charge per 1 cm3 of air (Johns andCunningham 1969). One rad is 100 ergs of energy absorbed from any type of radiation per gram ofthe absorber.

1 roentgen = 1 R = 2.58 x 10'4 coulombs/kg exposure

1 rad= 100 ergs

100 rads = 1 Gy= 1 J/kg

Therefore, an absorbed dose in air corresponding to a gamma-ray exposure of 1 roentgen, orcoulomb/kg amounts to 33.8 J/kg or 33.8 Gy or 3380 rads

Therefore, (for gamma-rays): 1 roentgen (R) = (3380 x 2.58 x 10"4) = 0.87 rads in air.

1 rem is defined as the unit of dose equivalent and is the product of the absorbed dose (D) rads anda quality factor (Q) or radiation weighing factor (Wr).

The quality factor (Q) = 1 for gamma-rays and X-rays

Therefore: 1 rem (dose equivalent) is numerically equal to 1 rad ~ 1.149 roentgens

100 rem =100 rads = 1 Gy = 1 Sv (sievert)

To obtain the absorbed dose in tissue, Dtissue (rads) from the exposure measured in air, E,«,(roentgens) the 'roentgens-to-rads' conversion factor, f tissue is used:5

Utissue ~" tissue * t ' air

\(ul p) tissue]where f^ =0 .869 \ ^ H> ,

[ (ft Ip)air J

and fj/p = mass energy absorption coefficients (m2/kg)

For 60Co gamma rays: /tissue = 0.96

DOSE CONVERSION IN AIR: 1 ROENTGEN = 0.87 RAD (1 RAD = 1.149 R)

DOSE CONVERSION IN TISSUE: 1 ROENTGEN = 0.96 RAD (1 RAD = 1.042R)

4. REFERENCES

1. Freedman, N.O., Aikens, M.S. and Szornel, K. The Radiation Biology and Health PhysicsBranch Irradiation Facility Uprgrade, AECL (Atomic Energy of Canada Limited), ChalkRiver, 1994 December.

2. AECL (Atomic Energy of Canada Limited), Instruction Manual Gammabeam 150 f°Coirradiation unit), Commercial Products, Edition No. 5, 1979 November.

3. AECL (Atomic Energy of Canada Limited), Instruction Manual for Gammacell 200 f°Coirradiation unit), Commercial Products, Edition No. 7, 1970 March.

4. AECL (Atomic Energy of Canada Limited), Operator's Manual for Gammacell 220 I60 Coirradiation unit), Commercial Products, Edition No. 7, 1978 March.

5. Spinks, J.W.T. and Woods, R.J. An Introduction to Radiation Chemistry, John Whiley &Sons Inc., Publ., New York (1964).

6. Johns, H.E. and Cunningham, J.R. The Physics of Radiology, Charles C. Thomas, Publisher,Springfield, Illinois (1969).

ACKNOWLEDGMENTS

The authors are grateful to N.O. Freedman for consultation during preparation of the report, toK.L. Gale for GammacelVbeam protocol preparation advice and support in the writing, and toK. Szornel, C.L. Greenstock, A.J. Waker, R.B. Richardson and P.A. Rochefort for assistance withdefinitions and revisions.

SHIELDING PLUS

3OURCZ APERTURC

SOURCEHEAO

ENCLOSURE

BEAM CONOlTlONINO1CATO* «0O

BEAM PORT HEAD

BEAM PORT

INTERLOCKTIMER

Figure 1: Gammabeam 150C

INTERLOCK PLUGA N D SOCKET(PG. 1 SK.1)

CONTROL PANEL

RUBBER KICKSTRIP

SHIELD PLUG

ORAWER TOP

SAMPLE CHAMBER DOOR

SAMPLE CHAMBER

'MICROFLEX'TIMER

MASTER KEYSWITCH (S.I)

FUSE (F.I)

DRAWER CONTROLROCKER SWITCH (S.2)

MANUAL CRANKACCESS PLUG BUTTON

FRONT STEP

Figure 2: Gammacell 200

10

TOP PLUGINTERLOCK MICROSWfTCH

COLLAR INTERLOCKMICROSWITCHES

TOP SHIELDING PLUG

•DRAWER TOP

DOOR INTERLOCK ASSEMBLY

SAMPLE CHAMBER DOOR

COLLAR HANDLES

CONTROL PANEL

-DRIVE MECHANISMACCESS PANEL

PLATFORM

Figure 3: Gammacell 220

11

GAMMABEAM 150C RADIATION FIELD(All measurements at 133 cm height)

September 12, 1994

Source ^Co 60, gamma)

50 cm Measurements

7 cm9.251 R/min 9.376 R/min

7 cm8.578 R/min

• 230 cm •

3.5 cm9.471R/min

3.5 cm9.397R/min

Figure 4: Gammabeam 150C Radiation Field (50 cm)

12

Gammabeam 150C Cross Section at 50 cm from Source

222 224 226 228 230 232 234

Distance from Right wall (facing source)

Figure 5: Gammabeam 150C Radiation Field Cross Section (50 cm)

236

13

GAMMABEAM 150CRADIATION FIELD

(All measurements made at 133 cm height)1994 September 12

392 cm Measurements

Soiree(Q6balt 60, gamma)

Figure 6: Gammabeam 150C Radiation Field (392 cm)

0 16

0.14 -

0.12 -

iene

0.08

0.06

0.04 -

0.02 -

14

Gammabeam 150C Cross Section at 392 cm

0 50 100 150 200 250 300 350 400 450Distance from Right Wall (facing source)

Figure 7: Gammabeam 150C Radiation Field Cross Section (392 cm)

15

GAMMABEAM 150CRADIATION FIELD

(All measurments at 133 cm height)1994 September 12

3 7 era «7era 137 em | h n 1* pt)0.022 Wmh 0.025 R/min 0.025 Mtm

SO on0JC7 Main 0.027 fVmii

ISO cm0.024 ftrmn

• 529 cm-

•2$7esi-

Figure 8: Gammabeam 150C Radiation Field (989.5 cm)

16

Gammabeam 150C Cross Section at 989.5 cm from Source

0.028

0.027 --

0.026 --

0.025 --

« 0.024 -

O

0.023 -

0.022

0.021 -

0.02

0 100 200 300 400 500Distance from Right Wall (facing source)

600

Figure 9: Gammabeam 150C Radiation Field Cross Section (989.5 cm)

17

THE GAMMACELL 200(Measurement Locations Within Sample Chamber)

The circled numbers indicate the relative dose as a percentage of the doseat the centre of the chamber (109.8 R/min - 1994 September 12).

Eo

CO

8.9 cm

Position 3

Position 2

Position 1

Figure 9a: Gammacell 200 Isodose Curves

18

ISODOSE CURVES GAMMACELL 200STANDARD LOADING

VERTICAL AXIS OF CHAMBER

8.9 cm INSIDE DIAMETEROF CHAMBER

The isodose distribution in the irradiation chamber of the Gammacell 200 unitwith standard loading should agree within +5% with the relative values shown.

The numbers indicate the relative dose expressed as a percentage of the dose at the centre of the chamber.(•Reproduced from Atomic Energy of Canada Ltd, Commercial Products (now NORDION), 1975 May)

Figure 9b: Gammacell 220 Radiation Field

19

TEE GAMMACELL 220(Measurement Locations Within Sample Chamber)

The circled numbers indicate the relative dose as a percentage of the doseat the centre of the chamber. (5.15 kR/min - 1994 September 12)

Position 3

Position 2

Position 1

Fiaure 10a: Gammacell 220 Isodose Curves

20

ISODOSE CURVES GAMMACELL 220STANDARD LOADING

VERTICAL AXIS OF CHAMBER

15.2 cm INSIDE DIAMETER . JOF CHAMBER

The isodose distribution in the irradiation chamber of the Gammacell 220 unitwith standard loading should agree within +5% with the relative values shown.

The numbers indicate the relative dose expressed as a percentage of the dose at the centre of the chamber.(•Reproduced from Atomic Energy of Canada Ltd, Commercial Products (now NORDION), 1980 January)

Figure 10b: Gammacell 220 Isodose Curves

X factor (1 month) = 0.01096

Months 0 1

T 1/2 = 5.27 years

ftU10203040

5060708090

100110120130140

0.89620.80320.71980.6451

0.57810.51810.46430.43610.3729

0.33420.29950.26840.24050.2156

0 Q8Q10.88640.79440.71200.6380

0.57180.51240.45920.41160.3688

0.33050.29620.26550.23790.2132

0 9783\s .7 1 OJ

0.87680.78580.70420.6311

0.56550.50680.45400.40710.3648

0.32690.29300.26260.23530.2109

0 96760.86730.77720.69650.6242

0.55940.50130.44930.40260.3608

0.32340.28980.25970.23270.2086

o0000

00000

00000

9571,7J / 1

.8578

.7687

.6889

.6174

.5533

.4958

.4444

.3982

.3569

.3199

.2866

.2569

.2302

.2063

ov.0.0.0.0.

0.0.0.0.0.

0.0.0.0.0.

94678484760368146107

54734905439639393530

31642835254122772041

o0.0.0.0.

0.0.0.0.0.

0.0.0.0.0.

93638391752067396040

54134851434738963492

31292804251322522018

0 9?fi?0.83000.74390.66660.5974

0.53540.47980.43000.38540.3453

0.30950.27740.24860.22280.1996

ft Q160\J. y 1 \j\J

0.82090.73570.65940.5909

0.52960.47460.42530.38120.3416

0.30610.27430.24590.22030.1974

0 Qftfi!\J, y\J\j 1

0.81200.72770.65210.5844

0.52380.46940.42070.37700.3379

0.30260.27140.24320.21790.1953

Table 1: Cobalt-60 Decay Table

22

APPENDIX A

Protocols

I GAMMABEAM 150 OPERATING PROCEDURE

II GENERAL INFORMATION

1. Only authorized personnel may operate this unit, as determined by the owner.

2. Before use, the operator will fill in the sign-out book located next to the door in Room 10,Bldg. 513 A. The information required is the operator's name, the anticipated length of timefor exposure and setup of equipment, if necessary.

3. After use, the key is returned to Room 10, Bldg. 513 A next to the signout book.

4. The complete manual for this instrument (as supplied by Nordion International) can be foundin Room 10, Bldg. 513 (please see the owner).

5. The sequence of operating instructions must be followed exactly, or the cobalt source cannotbe raised out of the lead castle.

6. For the unit to function, the back shipping door, located inside the irradiation room behindand to the left of the irradiator, must be tightly closed as this ensures proper functioning ofone of the interlock systems.

7. The large door leading into the irradiation room must also be tightly closed, to activate asecond interlock system. If this door is not tightly closed, the source cannot be raised.

8. A radiation detector is located inside the irradiation room and can be seen through thewindow to the left of the operating panel for this unit. It is pointed towards the source andthe monitor is located outside the beam room, to the left of the viewing window. Thedetector/monitor system act to operate the red flashing lights located inside the irradiationroom as well as outside over the interlock door in the control room. The flashing lightsindicate that a radiation field exists inside the beam room when the source is raised; however,the lights in the control room serve ONLY AS A VISUAL INDICATOR that the source is infact in the raised position.

9. If the source should become stuck in the raised position the emergency cable used tomanually lower the source is located in the storage room, to the left of the control room. Tolower the source in this manner, firmly grasp the emergency cable by the counter weight andpull down. This will cause the source to be lowered into the lead castle.

23

10. This facility has been monitored by Radiation Protection Branch (RPB) personnel. Allexterior walls and adjacent areas to this facility have been evaluated for radiation levels andall have been found to be at background values. The control room area has also beenmonitored and found to have background radiation levels, when the source is raised.

11. Radiation Protection Branch personnel monitor this facility, in particular the irradiator, forradiation levels when the source is lowered, and these levels are recorded on a smallchalkboard located on the front of the irradiator.

12. When work is being done on the roof (ceiling) of the beam room, the interlock key thatactivates the interlock on the door from the control room into the beam room will beremoved and held by building supervisor. This is a safety precaution that prevents the beamfrom being raised while work is being done on the roof of the facility.

13. Extensive dosimetry information for this facility is available in Room 10, Bldg. 513 A, abovethe signout book.

12 OPERATING INSTRUCTIONS

1. The control panel for the Gammabeam 150C (see Figure Al in Appendix A, Section 1) islocated in Bldg. 404B. Place the Gammabeam key (stored in Room 10, Bldg. 513 A) into slotA and turn to the right or left. The "power on" and "power trip" orange lights should now beon.

2. Ensure that the timer B is in the "D" mode and select the desired exposure time (this is a"countdown" timer). Also, check that the "safe/source down" toggle G is in the "safe toexpose" direction. Reset the elapse timer to keep track of the exposure time (this is a "countup" timer).

3. Enter the facility through the large door, taking the door interlock key C with you. Note thata green light is on above this door.

NOTE: If the interlock door is closed, remove the interlock key C and while pushing on thered button H, slide the door to the left. To open this door, power must be supplied to thecontrol panel (it will not open if the key A is not activating the control panel).

4. Place samples at the desired distance from the irradiator. A trolley designed for this purposeis available.

5. Before leaving the beam room, depress the red button located on the right front corner of thegreen bottom housing of the irradiator (you now have only 1 min to leave the room andactivate the unit or the timer must be reset).

6. Leave the room, close the door GENTLY and position the base of the door firmly against theangle iron "foot rest" on the floor.

24

7. Replace the door interlock key C and turn it 1/4 turn clockwise.

8. On the control panel, press the power reset button D, the timer reset button E and finally thestart exposure button F. You will now hear the source go up (you can check this by lookingthrough the window, to the left of the control panel).

9. Once the source is fully in the "up" position the detector will give an auditory signal, the redlights will be flashing inside the control and gamma beam rooms, and the source can be seenfully extended through the window. A red light will now be on above the interlock door.

10. At the end of the elapsed time, the source will drop down into the safe position automatically,and the green light will come back on above the interlock door.

11. If you want to stop the exposure before the elapsed time, switch the toggle G to the right(stop exposure). To restart the exposure, the above steps have to be repeated (you mighthave to recalculate your exposure time and make adjustments at the time).

25

POWER TRIP POWER ON SOURCE EXPOSED

A

POWER RESET

% TIME

BSOURCESAFE

PRESS TO EXPOSESOURCE

ELAPSED TIME

SAFE TOEXPOSE

TIMER SET

SOURCEDOWN

KG8M2-1S

• •«r Interlock

H

Figure Al: Gammabeam 150C Control Panel

26

2. GAMMACELL 200 OPERATING PROCEDURES

The Gammacell 200 has been designed to enable operating personnel to load the sample chamber andoperate the unit with a minimum exposure to radiation. To ensure protection, the following sequenceof operation is recommended.

1. With the drawer in the load (up) position, remove the sample chamber door by squeezing theclips at the top of the door.

2. The sample or accessory apparatus may now be placed in the sample chamber (see note 1).

3. Replace the sample door by inserting the lower edge into the register provided and pushingthe top edge forward until the door is properly seated.

4. Insert the Gammacell 200 key (stored in Room 10, Bldg. 513 A) into the control panel. Withthe toggle switch in manual control, the drawer can be raised or lowered by pressing the upor down switches. For auto control, set the required irradiation time by first dialing in thetime and selecting seconds, minutes or hours with the appropriate decimal place. Push thereset button to activate the timer and confirm the time set. Set the toggle switch to the autoposition. To lower the chamber push the down button. The drawer will lower the sampleinto the irradiating position, activate the timer and remain there until the preset time intervalhas elapsed when it will automatically return to the start position (see note 2)

5. To remove the sample, repeat steps 1 to 3.

NOTE 1: Material likely to change state during irradiation should be kept in suitable containers.Liquids expected to expand or boil should be provided with secondary containers for overflow orvented to the access tubes. Any accessory equipment should now be inserted into the access hole bylifting the top plug and taking care not to crimp cables etc when replacing the plug. Note that theinterlock will prevent usage, unless it is properly seated.

NOTE 2: On completion of a timed operation, the timer can be reset to the same operation time bydepressing the reset knob.

2.1 POWER FAILURE

In the event of a power failure the timer will stop, and it will be necessary to raise the drawermanually once the power has been restored.

3. GAMMACELL 220 OPERATING PROCEDURES

The Gammacell 220 has been designed to enable operation with minimum exposure of the operatorto radiation. To ensure protection, operators should adhere to the following procedures.

27

3 1 AUTOMATIC OPERATION

1. Insert the Gammacell 220 key (stored in Room 10, Bldg. 513 A) into the control panel.

2. To open the collar doors, press and hold in the button on the top of the door interlock, graspthe right-hand door handle, pull back the latch lever, release the button and pull the doorsopen.

3. Slide the sample chamber locking ring to the right, remove the door by lifting it up andoutwards.

4. Place the sample in the chamber (see note 3). The access tube in the drawer topaccommodates accessory tubes and electrical leads, which should be fitted in accordance withthe instructions provided in the Gammacell 220 Accessories Manual (available from theowner).

5. Replace the sample chamber door with a forward and downward motion. Move the lockingring to the left, until it snaps into position. If difficulties are experienced, check that the dooris correctly positioned in the port.

6. To close the collar doors, press and hold in the button on the top of the door interlock.Grasp the right-hand door handle, pull back the latch lever, release the button and push thedoors closed.

7. Set the required irradiation time by first dialing in the time and selecting seconds, minutes orhours with the appropriate decimal place. Push the reset button to activate the timer andconfirm the time set. Set the toggle switch to the auto position. To lower the chamber push,the down button. The drawer will lower the sample into the irradiating position, activate thetimer and remain there until the preset time interval has elapsed when it will automaticallyreturn to the start position. For manual operation, read the preceding steps 2 to 6, then selectmanual on the control panel. Press the down switch. The drawer will lower and remain thereindefinitely until the up switch is operated (see note 4).

NOTE 3: Materials expected to change state during irradiation should be placed in suitablecontainers. Liquids expected to expand or boil should be provided with secondary containersfor overflow, or vented to one of the access tubes. The sample chamber and source cage willnot withstand repeated spills or corrosive materials.

8. To remove the sample, repeat steps 2 and 3. Press the down switch. The drawer will lowerand remain there indefinitely, until the up switch is operated.

NOTE 4: On completion of a timed operation, the timer can be reset to the same operationtime by depressing the reset knob.

28

3.2 POWER FAILURE

In the event of a power failure the timer will stop, and it will be necessary to raise the drawermanually once the power has been restored.

29

4. KEITHLEY THERAPY DOSIMETER - OPERATING PROCEDURES

1. Select appropriate volume ion chamber for the desired working range. Connect to dosimeter.

2. Turn on dosimeter and allow it to warm up for 20 min. Check that the correct type of ionchamber is selected. Press "Detector Select" then the "up" or "down" arrow to step throughthe choices.

3. Press "Air Density" and use the arrow keys to step through selections for temperature (°C).Press "Air Density" again to select barometric pressure reading and adjust to correct pressureusing the arrow keys.

4. Press "Units Select" for readout in the correct range of interest. Use arrow keys to stepthrough choices.

5. Press "Bias Select" and make sure that -300 Vdc (100%) is selected. Note: Do notdisconnect detector lead when bias voltage or system power is on.

6. Press "Reset/Measure" twice to zero the instrument and get ready to start measurement.

4.1 NOTES:

Expose the detector for a short time (-100 s) before zeroing when using it for the first time that day.Leave power on if you are taking several readings over the day. Adjust the temperature andpressure if large fluctuations occur during a day.

30

APPENDIX B

Decay Charts

31

Table Bl. COBALT - 60 DECAY CHART FOR GAMMABEAM 150C (to 1999 DECEMBER)

(based on measurements made on 1994 September 12 - starting doses at centre of beam)

Date

Jan-96Feb-96Mar-96Apr-96May-96Jun-96Jul-96

Aug-96Sep-96Oct-96Nov-96Dec-96Jan-97Feb-97Mar-97Apr-97May-97Jun-97Jul-97



Aug-99Sep-99Oct-99Nov-99Dec-99

Decay Factor

0.83910.83000.82090.81200.80310.79440.78570.77710.76870.76030.75200.74380.73570.72770.71970.71190.70410.69650.68890.68140.67390.66660.65930.65210.64500.63800.63100.62420.61730.61060.60400.59740.59090.58440.57810.57180.56550.55940.55330.54720.54130.53540.52950.52380.51800.51240.50680.5013

No. of Months

01234567891011121314151617181920212223242526272829303132333435363738394041424344454647

Dose Rate(R/hr)

472.0466.9461.8456.8451.8446.8442.0437.2432.4427.7423.0418.4413.8409.3404.9400.5396.1391.8387.5383.3379.1375.0370.9366.8362.8358.9355.0351.1347.3343.5339.7336.0332.4328.8325.2321.6318.1314.7311.2307.8304.5301.2297.9294.6291.4288.2285.1282.0

at 50 cm(R/min)

7.8677.7817.6967.6137.5307.4477.3667.2867.2077.1287.0506.9736.8976.8226.7486.6746.6026.5306.4586.3886.3186.2506.1816.1146.0475.9815.9165.8525.7885.7255.6625.6015.5405.4795.4205.3605.3025.2445.1875.1315.0755.0194.9654.9104.8574.8044.7524.700

Dose Rate(R/hr)

7.447.367.287.207.127.046.976.896.826.746.676.596.526.456.386.316.246.186.116.045.985.915.855.785.725.665.605.535.475.415.365.305.245.185.135.075.014.964.914.854.804.754.704.644.594.544.494.44

at 392 cm(R/min.)

0.1240.1230.1210.1200.1190.1170.1160.1150.1140.1120.1110.1100.1090.1080.1060.1050.1040.1030.1020.1010.1000.0990.0970.0960.0950.0940.0930.0920.0910.0900.0890.0880.0870.0860.0850.0840.0840.0830.0820.0810.0800.0790.0780.0770.0770.0760.0750.074

Dose Rate(R/hr)

1.381.361.351.341.32.31.29

1.281.261.251.241.221.211.201.181.171.161.151.131.121.111.101.081.071.061.051.041.031.021.000.990.980.970.960.950.940.930.920.910.900.890.880.870.860.850.840.830.82

at 989.5cm(R/min)

0.0230.0230.0230.0220.0220.0220.0220.0210.0210.0210.0210.0200.0200.0200.0200.0200.0190.0190.0190.0190.0180.0180.0180.0180.0180.0170.0170.0170.0170.0170.0170.0160.0160.0160.0160.0160.0160.0150.0150.0150.0150.0150.0150.0140.0140.0140.0140.014

Dose is proportional to 1/(distance squared)Dose = K/d2

32

Table B2. COBALT-60 DECAY CHART FOR GAMMACELL 200 (TO 1999 DECEMBER)

(based on measurements made 1994 September 12 - centre of chamber =109.8 RAnin)1 R (roentgen) = 87 Gy (gray) (in air) or 96 Gy (in tissue)

Time of Dose Required = (dose - deadtime dose) dose rate

Date






Decav Factor

0.83910.83000.82090.81200.80310.79440.78570.77710.76870.76030.75200.74380.73570.72770.71970.71190.70410.69650.68890.68140.67390.66660.65930.65210.64500.63800.63100.62420.61730.61060.60400.59740.59090.58440.57810.57180.56550.55940.55330.54720.54130.53540.52950.52380.51800.51240.50680.5013

No. of Months

01234567891011121314151617181920212223242526272829303132333435363738394041424344454647

Dead-time Dose(roentgens)

7.557.477.397.317.237.157.076.996.926.846.776.696.626.556.486.416.346.276.206.136.066.005.935.875.805.745.685.625.555.495.435.385.325.265.205.145.095.034.984.924.874.824.764.714.664.614.564.51

Dose Rate(R/s)

1.541.521.501.491.471.451.441.421.411.391.381.361.351.331.321.301.291.271.261.251.231.221.211.191.181.171.161.141.131.121.111.091.081.07.06.05.04.02.01.00

0.990.980.970.960.950.940.93().92

Dead-Time Dose(cGy in tissue)

7.257.177.097.016.946.866.796.716.646.576.506.426.356.296.226.156.086.025.955.895.825.765.705.635.575.515.455.395.335.275.225.165.105.054.994.944.884.834.784.734.684.624.574.524.474.434.384.33

Dose Rate(cGy/s in tissue]

1.471.461.441.431.411.401.381.371.351.341.321.311.291.281.261.251.241.221.211.201.181.171.161.15.13.12.11

1.10.08.07.06.05.04

1.031.021.000.990.980.970.960.950.940.930.920.910.900.89().88

Table B3.

33

COBALT-60 DECAY CHART FOR GAMMACELL 220 fTO 1999 DECEMBER)

(based on measurements made on 1994 September 12 - central point of chamber = 5.15 kR/min)1 R (roentgen) = 87 Gy (gray) (in air) or 96 Gy (in tissue)

Time of Dose Required = (dose - deadtime dose) dose rate

Date



Aug-97Sep-97Oct-97Nov-97Dec-97Jan-98Feb-98Mar-98Apr-98May-98Jun-98M-98



Decay Factor

0.83910.83000.82090.81200.80310.79440.78570.77710.76870.76030.75200.74380.73570.72770.71970.71190.70410.69650.68890.68140.67390.66660.65930.65210.64500.63800.63100.62420.61730.61060.60400.59740.59090.58440.57810.57180.56550.55940.55330.54720.54130.53540.52950.52380.51800.51240.50680.5013

No. of Months

01234567891011121314151617181920212223242526272829303132333435363738394041424344454647

Dead-Time Dose(kR)

0.34960.34580.34200.33830.33460.33100.32730.32380.32030.31680.31330.30990.30650.30320.29990.29660.29340.29020.28700.28390.28080.27770.27470.27170.26870.26580.26290.26000.25720.25440.25160.24890.24620.24350.24080.23820.23560.23300.23050.22800.22550.22310.22060.21820.21580.21350.21120.2089

Dose Rate(kR/min)

4.3214.2744.2274.1814.1364.0914.0464.0023.9583.9153.8723.8303.7883.7473.7063.6663.6263.5863.5473.5093.4703.4333.3953.3583.3223.2853.2503.2143.1793.1443.1103.0763.0433.0102.9772.9442.9122.8802.8492.8182.7872.7572.7272.6972.6682.6392.6102.581

Dead-Time Dose(Grays in tissue)

3.35623.31963.28343.24763.21223.17723.14253.10833.07443.04093.00772.97502.94252.91052.87872.84742.81632.78562.75522.72522.69552.66612.63712.60832.57992.55182.52392.49642.46922.44232.41572.38932.36332.33752.31212.28692.26192.23732.21292.18882.16492.14132.11802.09492.07202.04942.02712.0050

Dose Rate(Gy/minin tissue)

41.4841.0340.5840.1439.7039.2738.8438.4238.0037.5837.1836.7736.3735.9735.5835.1934.8134.4334.0533.6833.3232.9532.5932.2431.8931.5431.2030.8630.5230.1929.8629.5329.2128.8928.5828.2727.9627.6527.3527.0526.7626.4726.1825.8925.6125.3325.0524.78

AECL-11567

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Copyright © Atomic Energy of Canada Limited, 1996

B.P. Smith, RE. Lee

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