IEC 60405-2003 pdf – Nuclear instrumentation- Constructional requirements and classification of radiometric gauges.
1 Scope and object This International Standard applies to the manufacture and installation of electrical measuring systems and instruments utilizing radioactive sources (radiometric gauges, hereinafter called gauges). It does not apply to portable gauges which, because of their construction and purposes for use, are intended to be operated as mobile equipment and it does not apply to gauges operated with X-ray tubes, but it can be analogously applicable to these gauges. The purpose of this standard is to specify constructional requirements for the design of instruments and the radiation protection to be provided in the case of radiometric gauges. In this context, special attention is attached to the stability of the source housing in the event of fire. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60476:1993， Nuclear instrumentation – Electrical measuring systems and instruments utilizing ionizing radiation sources – General aspects IEC 60692:1999， Nuclear intrumentation – Density gauges utilizing ionizing radiation – Definitions and test methods IEC 60982:1989， Level measuring systems utilizing ionizing radiation with continuous 01 switching output IEC 61010-1:2001, Safety requirements for electrical equipment for measurement, control and laboratory use – Part 1: General requirements
5 General requirements 5.1 Measuring gap In order to prevent persons placing their hands or any other part of their body in the useful beam, the gauges shall be constructed in such a way that the measuring gap is kept to a practical minimum. This also includes any other points where access to the useful beam is likely to occur. If necessary, the user shall install additional protective devices. 5.2 Source holder The source holder shall be designed and constructed in such a way that: a) an easy installation of the radioactive source is feasible under radiologically safe conditions; . b) a reliable positioning of the source is feasible under radiologically safe conditions. 5.3 Source housing The source housing shall be designed and constructed in such a way that: a) the radioactive source is protected under normal operating conditions against impacts which could damage it if no other means are provided in the gauge for such protection; b) dismantling of the radioactive source by non-authorized persons is prevented (e.g. by pro- viding a safety lock, special tools which are necessary to open the housing, or by security sealing procedures); c) it withstands the adverse physical and chemical influences expected in accordance with the user’s information (e.g. by means of installing an additional protective hood or any other installation-related measures); d) the radioactive source is secured in a manner to prevent the radioactive source from falling out even in the event of mechanical damage to the housing or in case of fire; e) it is possible to carry out source leakage tests under radiologically safe conditions.
5.5 Other requirements In addition to the specified constructional requirements, the gauges shall comply with the provisions as laid down in the respective valid version of the appropriate national regulations currently in force. Additional non-safety relevant information on instruments and systems for which this standard is applicable is given in IEC 60692, IEC 60982 and IEC 61336. General constructional require- ments for electrical measuring, control and laboratory instruments are given in IEC 61010-1. Electromagnetic compatibility (EMC) requirements are given in IEC 61326. Safety requirements and tests for classification of the sealed sources used in the gauges are given in ISO 2919. 6 Protection against ionizing radiation 6.1 General requirements The shielding of the gauge shall be so designed, or the gauge shall be installed, in such a way that the dose equivalent rate at the points which are accessible for non-occupationally exposed persons does not exceed the values specified in appropriate national regulations pertaining to continuously occupied working places. The accompanying documents should include information that it is the responsility of the user to observe the radiation labelling and shielding or barriers and to ensure that the actual limit values, specified in appropriate national regulations, are not exceeded. 6.2 Requirements for Category A gauges The source housing shall ensure that the dose equivalent rate for the respective radiation protection class is adhered to in accordance with 4.3. The source housing shall be equipped with shutters for interrupting the useful beam. If the device is remote-controlled or servo-controlled for safety reasons, any failure of the control circuits (e.g. failure of power supply) shall automatically close the shutter. After elimination of the fault, the shutter shall not automatically open until the system is intentionally returned to its normal operating mode .