 ·Home
·Table of Contents
·Methods and Instrumentation | ISO 3999 (2000) - Radiation Protection Apparatus for Industrial Gamma Radiography in Transition to the 3rd Millennium
Authors :
Camille Laduron, MDS Nordion Industrial Radiography, Operations Director
Vincent Vander Bracht, MDS Nordion Industrial Radiography, Area Sales Manager
Véronique Meurisse, MDS Nordion Industrial Radiography, Regulatory Affairs
Co-authors :
Rudiger Grimm, MDS Nordion Haan GmnH, Managing Director
Karl Weinlich, MDS Nordion Haan GmbH, Development Management Mechanics
Contact
|
Introduction
The recent years have seen profound changes in the world of gamma radiography.
Those of you familiar with early gamma projectors will remember a lead shielded container equipped with a simple lock intended to prevent the source from falling out. Nothing in the container design was intended to prevent exposure incidents, whether voluntary or accidental, and to protect users or bystanders.
Equipment manufacturers now have to meet the requirements of the newly adopted ISO 3999-1 : 2000 standard. The standard specifies tests that are intended to ensure that equipment, accessories and sources can be used with greater safety. Any modification to already ISO 3999-1 : 2000 compliant equipment, accessory or source cannot be implemented until the test series has been repeated successfully with the modifications proposed.
The scope of the ISO 3999-1 norm is to specify the performances, the design and the tests requirements of apparatus for gamma radiography, and is no substitute for satisfying the requirements of international relevant transport regulations (AIEA regulations).
The following document provide a comparison of the main test requirements of ISO 3999-1 : 2000 and of the tests performed on Gammamat® equipment, as well as a comparison of MDS Nordion radioactive sealed sources and of the ISO 2919 : 1999 classification requirements.
Destructive Testing of the Projector
Drop Tests on Type B Units
Although not required by the ISO 3999-1 : 2000 norm, 9 metre drop tests have been performed on Gammamat® type B units. Shielding integrity was successfully demonstrated after 4 drops on the same unit.
Accidental puncture test, although only required for type A units, have also been completed on type B units with satisfactory results.
Drop Test on Type A Units
For type A units, ISO 3999-1 : 2000 specifies an accidental puncture test consisting in 1 drop of the unit from 1.8 meter. After the test, the unit shall operate correctly.
Four drops from 1 meter on a steel billet have been performed on the same Gammamat®.
The 1.8 meter accidental puncture test was successfully completed and followed by the vertical shock test (see below).
Furthermore, the unit was submitted to a 9 meter drop test, not requested by the norm.
Integrity of shielding and operation were maintained.
Horizontal Shock Test
Shock tests were successfully completed on the front side and the back side of Gammamat® type A and type B units (20 tests on each side). Correct operation of the units was verified in full accordance with the requirements of ISO 3999-1 : 2000.
Vertical Shock Test
Shocks tests were performed from a height of 150 mm on Gammamat® type B unit, as requested by the norm.
Shocks tests were performed from a height of 180 mm on Gammamat® type A unit, where the norm only request shocks from 150 mm.
The Gammamat® devices remained fully functional a the conclusion of the tests.
The results of the above mentioned tests show that Gammamat® units successfully underwent tests exceeding the ISO 3999-1 : 2000 requirements
Endurance Testing of the Projector and Components
ISO 3999-1 : 2000 specifies an endurance test of 50,000 cycles to be performed on complete unit assemblies projector, remote control and guide tube This test is requested for type B and type A units.
Over 100,000 cycles were completed on a type B unit assembly . At the end of the test series, the device and its components still operated correctly .
Over 70,000 cycles were completed on a type A unit assembly with the same results the device and components.
The results of the above mentioned tests show that Gammamat® unit successfully underwent tests exceeding the ISO 3999-1 : 2000 requirements.
Destructive Testing of the Source Guide Accessories
To comply with the requirements of ISO 3999-1 : 2000, destructive tests have to be performed on the main accessories: source holder, remote control and exposure tube.
Tensile Test on Source Holder
Gammamat® source holders underwent 10 tensile tests of 5 seconds each at 1,000 N as per the requirements of the norm.
The source holder assemblies successfully completed the test series and remained intact.
Tensile Test on Remote Control
Gammamat® remote control cable underwent 10 tensile tests of 10 seconds each at 1,000 N as per the requirements of the ISO 3999-1 : 2000 norm.
Gammamat® remote control sheath also underwent 10 tensile tests of 30 seconds each at 500 N as per the requirements of the ISO 3999-1 : 2000 norm.
The remote control assembly remained operational after the test.
Tensile Test on Exposure Tube
Gammamat® exposure tube underwent 10 tensile tests of 30 seconds each at 500 N as per the requirements of the ISO 3999-1 : 2000 norm.
The exposure tube remained operational after the test.
Kinking Test on the Remote Control and Exposure Tube
A kinking test has been performed on Gammamat® remote control and exposure tube according to the requirements of ISO 3999-1 : 2000.
The tubes remained operational after the test.
Crushing Test on the Remote Control and Exposure Tube
A crushing test has been performed on Gammamat® remote control and exposure tube according to the requirements of ISO 3999-1 : 2000.
The remote control and exposure tube remained operational after the test.
The results of the above mentioned tests show that Gammamat® units and components successfully underwent the tests requirements of the ISO 3999-1 : 2000.
Positive Source Detection and Indication - Source Locking System Testing
On both type A and type B units, the Gammamat® source locking system also acts as a positive source detection and position indication system.
Where ISO 3999-1 : 2000 requires that the device automatically locks upon return of the source holder in the shield, only the Gammamat® locking system can confirm that the source itself is back.
The results of the above mentioned tests show that the Gammamat® unit and its components successfully completed the tests requirements of ISO 3999-1 : 2000.
Surface Radiation Levels Measurements
The ISO 3999-1 : 2000 admissible leakage radiation level is 2 mSv/h contact and 20 µSv/h at 1 meter.
This norm is more strict than the AIEA Transport Regulations
The first type B unit is licensed for Ir-192 sources up to 3 TBq (80 Ci)
Tests have been made with a 3 TBq source and maximum doses of 1.03 mSv/h on contact and 8 µSv/h at 1 meter have been recorded.
The second type B unit is licensed for Ir-192 sources up to 5 TBq (135 Ci)
Tests have been made with a 5 TBq source, and maximum doses of 0.99 mSv/h on contact and 9.1 µSv/h at 1 meter have been recorded.
The type A unit is licensed for Se-75 sources up to 3 TBq (80 Ci). This value corresponds to the type A limit defined in the AIEA Regulation.
Tests have been made with a 2.7 TBq source containing Sc-42 and results have been calculated by extrapolation for a 3 TBq source. Maximum doses of 1.93 mSv/h on contact and 5 µSv/h at 1 meter have been recorded.
The results of the above mentioned tests show that Gammamat® units and components successfully underwent the tests requirements of the ISO 3999-1 : 2000.
Conclusion of the tests performed on Gammamat® units
The severity of tests performed on Gammamat® units and components have demonstrated the compliance to the ISO 3999-1 : 2000 norm.
Radioactive Sealed Sources
The ISO 3999-1 : 2000 standard refers to the test requirements of ISO 2919 : 1999 for radioactive sources, including those requirements for the fire test.
MDS Nordion sources have long been tested up to 1,200°C according to the AFNOR norm NF M 61-002 where ISO 2919 : 1999 only requires this test up to 800°C.
The launch by MDS Nordion of doubly encapsulated Se-75 sources raised questions about the behaviour and safety of Se-75 in high temperature fires (such as those that would result from fires in petrochemical installations).
Behaviour of Se-75 beyond temperatures of 800° C can be problematic as outlined in a January 1999 internal report prepared by Dr. Ballaux of AV Controlatom, Belgium. In response to the concerns expressed by Dr. Ballaux, MDS Nordion submitted its SR17 capsule model to tests involving temperatures of 900° C, 1,000° C and 1,200° C for one hour.
A first series of fire tests performed at 800, 900 and 1,000° C showed that the capsules remained leaktight. After one hour at 1,200° C, the following observations were made :
The external diameter of the capsules was slightly diminished (from 0.03 to 0.1 mm)
Changes occurred in the welded areas and in the walls of the capsules : increase in grain size and microhardness. Nevertheless, the external capsules remained leaktight.
In the face of overwhelming evidence showing the ability of the SR17 capsule to withstand temperatures up to 1,200° C for 60 minutes, a joint communiqué was prepared and signed by Controlatom, MDSN and former ITS. Dr. Ballaux's final report was published in the annals of Health Physics, Vol. 78, No 3, March 2000.
In addition, routine tensile tests are performed on all MDS Nordion source holder (Gammamat® and others).
Conclusion:
Today, all gamma radiography equipment sold must meet precise and stringent safety requirements, regardless of manufacturers.
The requirements of ISO 3999-1 : 2000 and the manufacturing requirements of ISO 9001-9002 together will result in greater safety for all, something MDS Nordion is committed to as indicated in its motto:
Science Advancing Health