This standard specifies the basic requirements for nuclear criticality accident dose measurement, the performance of dose measurement systems and the dosimeter setting criteria. This standard applies to places or facilities where nuclear criticality accidents may occur and may cause personnel to suddenly be exposed to penetrating radiation that significantly exceeds the annual dose limit specified by the state. GB 15847-1995 Nuclear criticality accident dose measurement GB15847-1995 standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Dosimetry for criticality accidents
Dosimetry for criticality accidents1 Subject content and scope of application
GB15847—1995
This standard specifies the basic requirements for nuclear criticality accident dose measurement and the performance of dose measurement systems and dosimeter setting criteria. This standard applies to places or facilities where fissile materials are operated, processed or stored, where nuclear criticality accidents may occur and personnel may suddenly be exposed to penetrating radiation that significantly exceeds the annual dose limit specified by the state. 2 Referenced standards
GB15146.9 Nuclear criticality safety of fissile materials outside reactors Performance and inspection requirements for nuclear criticality accident detection and alarm systems
3 Terminology
Dose measurement system: A system consisting of detectors or dosimeters and related data collection and processing equipment, as well as technology for deriving absorbed doses of exposed personnel from measured data.
4 Basic requirements
4.1 All places where fissile materials are operated, processed or stored must be investigated to evaluate whether they need to establish a nuclear criticality accident dose measurement system. When determining this need, the characteristics of the relevant fissile material operations and the physical form, chemical composition and isotopic composition of the fissile materials should be considered.
4.2 A nuclear criticality accident dose measurement system must be established in places where there is a risk of accidental nuclear criticality accidents and may cause personnel to suddenly be exposed to penetrating radiation that significantly exceeds the annual dose limit specified by the state. As a general rule, all operations or places where a nuclear criticality accident alarm system is required to be installed in accordance with the provisions of GB15146.94.2 should be equipped with a criticality accident dose measurement system. 4.2.1 The dose measurement system should be able to provide absorbed dose data within the first 24 hours of a nuclear criticality accident. 4.2.2 The dose measurement system should include personal dosimeters and positioned dosimeters. Moreover, generally, personal dosimeters should be used as the main measurement means, and fixed-position dosimeters should be used as supplementary measurement means. 4.2.3 If fixed-position dosimeters are used as the main measurement means, a personal dose measurement system must be used at the same time so that the data provided by the fixed-position dosimeters can be extrapolated to obtain the exposure dose of the exposed person. 4.2.4 Measures that can determine the position and posture of the person when exposed must be arranged in advance. Techniques suitable for making such judgments may include analysis of induced radioactivity in human hair and personal belongings and investigation and understanding of the exposed person. 4.2.5 The various calibrated instruments and techniques that make up the dose measurement system must be maintained to ensure that they are available at any time. These instruments and techniques should include counting systems for measuring activated foil induced radioactivity, data readout systems for gamma-ray dosimeters, and sample preparation methods for measuring induced radioactivity in biological samples, as well as procedures or methods for deriving the absorbed dose of the exposed person from direct measurement data.
4.2.6 If a dose meter using radioactive material is damaged by fire and will significantly increase the contamination of the vicinity or factory building where it is located, it should be placed in a fireproof container. For dose meters used in chemical processing areas, measures to prevent chemical corrosion should be considered. 4.2.7 A method must be established to obtain preliminary dose estimates in a timely manner. The method should be able to measure dose values ​​as small as 0.1y to distinguish those who are significantly exposed. The methods that can be used include measuring the induced radioactivity of activated foil or portable metal objects located on personal dosimeters, or measuring the induced radioactivity of exposed human bodies. 5 Performance criteria for dose measurement systems
5.1 The dose measurement system should be able to provide sufficient data so that the calculation results of absorbed dose in or on the phantom can be accurate to ±25% under laboratory test conditions similar to the neutron and radiation energy spectrum and injection in nuclear criticality accidents. 5.2 The response range of neutron and radiation dosimeters should be from 0.1Gy to at least 10Gy. 5.3 The dose meters must be protected from radioactive contamination to obtain correct measurement results. 5.4 Appropriate procedures or measures must be taken to correct or eliminate the effects of high radiation background and high neutron background on accident dose estimation. 6 Design criteria for dose measurement systems
6.1 The number of dose meters required and their arrangement should be determined based on the design and operation characteristics of the facility, the accessibility of various parts and the relevant requirements in Chapter 4 of this standard.
6.2 The distribution of the positioned dose meters should ensure that a measurable response can be obtained for the smallest nuclear criticality accident occurring at any location in the operating area. The maximum distance between the dosimeters of the positioning arm and the fissile material can be estimated based on the requirement that the dosimeter can measure at least about 0.1Gy of total neutron and radiation dose under the minimum total number of fissions. When making this estimate, 101° fissions can be used as the minimum total number of fissions; and the expected neutron leakage energy spectrum and the relative dose contribution of neutrons and radiation under accident conditions should also be considered. 6.3 When selecting the placement of the positioning dosimeters, the interference shields and obstacles between the dosimeters and the area where the fissile material is located should be minimized. wwW.bzxz.Net
6.4 When selecting the placement of the positioning dosimeters, the ease of retrieval of these dosimeters should be considered. The retrieval of the dosimeters must be carried out according to the pre-established procedures. Such procedures must not delay the evacuation of personnel, and the personal risks to the operators in performing such procedures must not be greater than the acceptable level during normal operation.
6.5 Appropriate management procedures must be established to ensure that the layout of dosimeters is reassessed regularly (or when the factory situation changes): and to ensure that dosimeters are not moved or re-placed at will. 6.6 Personnel working in places that have been identified and confirmed to require nuclear criticality accident dose measurement should be allocated and wear personal dosimeters. The police department should enforce the relevant requirements for wearing personal dosimeters. Additional notes:
This standard was proposed by China National Nuclear Corporation. This standard was drafted at the expense of the Nuclear Industry Standardization Institute. The main drafters of this standard are Gao Fengguan and Hao Luping. This standard refers to the American national standard ANSIN13.3 "Nuclear Criticality Accident Dose Measurement". 718
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