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Technical Information for Radiation Sources

Definitions

Sealed Source:

Radioactive material sealed in a capsule that is strong enough to prevent dispersion of the radioactive material under the conditions of use for which it was designed. Also an assemblage of sealed sources in array utilized in an irradiator. (IAEA Safety Series No. 107, 1992)

Activity:

Activity of sources is expressed as “equivalent activity” defined as the activity equal to the activity of a point source of the same radionuclide which gives the same exposure rate at the same distance from the centre of source.

Activity tolerance: ± 10%.

Source Working Life:

The “recommended working life” (RWL) is our recommendation of the period within which the source should be replaced.

This information is given in the Test Report. The period has been assessed on the basis of such factors as, toxicity of nuclide, total initial activity, source construction (capsule design, source insert type, etc.) half-life of nuclide, typical application environments, operational experience, test performance data.

The relationship between equivalent activity and exposure rate is different for each radionuclide, depending on the type and quantity of radiation emitted in each nuclear transformation.

The equivalence between the old and the new units

Nuclide Equivalent Activity Exposure Rate
at 1 Meter
Absorbed Dose-rate
in Air at 1 Meter (approx.)
Cobalt-60 1 Ci 1.30 R/h 11 mGy/h
Iridium-192 1 Ci 0.48 R//h 4.2 mGy/h

ICRU have approved the following SI units for radioactivity and absorbed dose

Physical Quantity SI Unit Traditional Unit Relationship
Radioactivity Becquerel (Bq) Curie (Ci) 1 Ci = 3.7×1010 Bq
1 Bq = 2.70×10-11 Ci
Absorbed Dose Gray (Gy) Rad 1rad = 0.01 Gy
1 Gy = 100 rad

Sealed Source Performance Requirement for Typical Use

SEALED SOURCE USE SEALED SOURCE TEST AND CLASS
Temperature Pressure Impact Vibration Puncture
Radiography-Industrial
1. Unprotected Source 4 3 5 1
2. Source in Device 4 3 3 1 3
Medical
1. Radiography 3 2 3 1 2
2. Teletherapy 5 3 5 2 4
3. Needles / Implants 5 3 2 1 1
4. Surface Applicators 4 3 3 1 5
Medium and High Frequency γ -Gauges
1. Unprotected Source 4 3 3 3 3
2. Source in Device 4 3 2 3 2
Low-energy ß, γ or Fluorescence
Analysis X-ray-source Instruments

(Excluding Gaseous Sources)
3 3 2 2 2
Radioactive Carottage 5 6 5 2 2
Portable Moisture Density Gauges
(Incl. Hand-held and Dolly Transported)
4 3 3 3 3
General Neutron Source Application
(Excluding Reactor Start-up)
4 3 3 2 3
(MSZ 14339/2.)

Classification of Sealed Sources

Test Temperature External Pressure Impact
from 1 m
Vibration Puncture
from 1 m
1. No test No test No test No test No test
2. -40°C (20 min)
+80°C (1 h)
0.025 MPa to atmospheric pressure 50 g 3 x (10 min) 25 Hz to 500 Hz at 49.05
m/s2 (5g) peak acceleration amplitude
0.001 kg
3. -40°C (20 min)
+180°C (1 h)
0.025 MPa to 2.0 MPa 200 g 3 x (10 min) 25 Hz to 50 Hz
at 49.05 m/s2 (5g) peak amplitude
and 50 Hz to 90 Hz at 0.635 mm amplitude
peak to peak and 90 Hz to 500 Hz
at 98.1 m/s2 (10g) peak acceleration amplitude
0.01 kg
4. -40°C (20 min)
+400°C (1 h)
and thermal shock
400°C to 20°C
0.025 MPa to 7.0 MPa 2.0 kg 3 x (10 min) 25 Hz to 80 Hz 1.5 mm
amplitude peak to peak and 80 Hz
to 2000 Hz at 196.2 m/s2 (20g)
peak acceleration amplitude
0.05 kg
5. -40°C (20 min) +600°C (1 h)
and thermal shock
600°C to 20°C
0.025 MPa to 70 MPa 5.0 kg 0.3 kg

6. -40°C (20 min) +800°C (1 h)
and thermal shock
800°C to 20°C
0.025 MPa to 170 MPa 20.0 kg 1.0 kg

Controls

Testing for Leakage Contamination

The standard methods used routinely for each source are as follows

Wipe Test “A”

The source is wiped with a swab moistened with distilled water. The activity removed must not exceed: 185 Bq (0.005 ľCi).

Wipe Test “B”

The procedure is the same as with test “A”, but the activity removed must not exceed 1.85 kBq (0.05 ľCi).

Ultrasonic Test

The source is placed in a reservoir of an ultrasonic equipment for 1 hour. The equipment must guarantee at least 40 watts as output. The activity of the handling solution measured after the testing procedure must not exceed 185 Bq (0.005 ľCi). Sources found to be free of contamination and leak are held for seven days and retested.

Ultrasonic Test “A”

The handling solution in the reservoir is 1.5 mol/l HNO3

Ultrasonic Test “B”

The handling solution in the reservoir is 1.5 mol/l HCl.

Ultrasonic Test “C”

The handling solution in the reservoir is distilled water.

Vacuum Bubble Test

Using analytical reagent grade ethylene glycol, water, or oil as the leak-test fluid in a suitable vacuum chamber, lower the air pressure to atmospheric and submerge the sealed source to depth of at least 5 cm below the fluid level. Reduce the absolute pressure in the chamber to 15-25 kPa. Observe for bubbles emanating from the sealed source over a period of not less than 1 min. If none are observed, the sealed source is considered to have a leak-rate less than 1.33×10-6 Pa m3/s and is considered to be leak-free.

Prototype Test

Besides the individual tests each type of the source capsules is tested by the prescription of the Hungarian standard MSZ 14339/2, which is based on ISO 2919 (Sealed radioactive sources Classification) and fully corresponds to ST CMEA 3839-82.

Radiation Sources

Industrial Sources (Cobalt-60)

Sources for Gauges (Cobalt-60)

Gamma Radiography Sources (Iridium-192)

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