1 Scope
This document specifies the methodology for the development and revision of operational intervention levels for reactor emergency conditions. This document applies to pressurised water reactors and may also be used for other types of reactors.
2 Normative references
The contents of the following documents constitute essential provisions of this document by means of normative references in the text. Among them, note the date of the reference documents, only the date of the corresponding version applicable to this document; do not note the date of the reference documents, its latest version (including all the revision of the list) applicable to this document.
GB18871-2002 Basic standard for ionising radiation protection and safety of radiation sources
3 Terminology and definitions
The following terms and definitions apply to this document.
3.1
Intervention level
The preventable dose level established for an emergency exposure situation or a continuous exposure situation. Note: When such a preventable dose level is reached, the appropriate protective or remedial action is considered.
[Source: GB18871-2002, J6.10, with modifications].
3.2
Action level
The dose level or activity concentration level at which remedial or protective action is to be considered in the case of continuous or emergency exposures. [Source: GB 18871-2002, J6.11, with modifications]
3.3
Operational intervention levels operational intervention levels; the values derived from the corresponding generic intervention levels or generic action levels for oIL.
Note: Operational intervention levels are quantities that can be directly compared with instrumental measurements or laboratory analyses, e.g. peripheral dose equivalent rates in radioactive plumes, radionuclide concentrations, etc.
3.4
Preventable doseavertable dose
The dose reduced by taking protective action, i.e. the difference between the dose that would be expected if protective action were taken and the dose that would be expected if no protective action were taken.
[Source: GB 18871-2002, J6.9].
4 Purpose of the operational intervention level application
The following objectives are achieved through the implementation of the intervention level and the application of the operational intervention level. a) Prevention of deterministic effects (death and injury) through the following measures:
Acting before or for a short time after a reactor accident resulting in a large release of radionuclides;
keeping the dose to the public below the threshold for deterministic effects (as required by Appendix A).
b) Implement protective actions to reduce the risk of stochastic health effects (mainly cancer and severe genetic effects) in accordance with 10.3 of GB 18871-2002.
b) Implement protective actions to reduce the risk of stochastic health effects (mainly cancer and serious genetic effects) in accordance with 10.3 of GB 18871-2002. Deterministic health effects can be prevented by taking protective actions prior to or within a short time after the release of radionuclides. The actions taken should be based on the reactor's operating conditions and then refined based on the results of environmental measurements. Protective actions based on ambient dose equivalent rates and environmental sample analysis can reduce the risk of stochastic health effects. The use of ambient dose equivalent rates or sediment activity concentrations can facilitate the identification of areas requiring restrictive measures, and sampling and analysis can be used to assess the safety of food, milk and drinking water in general.
5 Development of operational intervention levels
5.1 Types of operational intervention levels
When the corresponding instrumental monitoring result or laboratory analysis exceeds the operational intervention level, it is appropriate to take appropriate protective action. The establishment of an operational intervention level is one way of making a judgement on the basis of the measurement results, but it is not the only way. In the early stages of a particularly urgent accident, it is more important to take precautionary protective action based on reactor operating conditions rather than measurement results. The types of operational intervention levels include:
5.2 Default values for operational intervention levels
The default values for Operational Intervention Levels are calculated a priori based on the assumption that a core meltdown without attenuated release of radioactivity leads to a severe accident and the associated assumptions.The default values for OIL1 to OIL9 and the corresponding measurement categories are shown in Table 1.
5.3 Description of default values for operational intervention levels
5.3.1 Description of oIL1
5.4 Determination of the initial values of the operational intervention levels
The default values for the operational intervention levels are calculated a priori on the basis of the incident characteristics and the relevant assumptions. The dose parameters required for OILl and OIL2 are related to the nature of the accident and the plant site environment. During the emergency preparedness phase, initial values for the operational intervention levels OIL1 and OIL2 need to be established according to the type of accident, meteorological and other conditions that are applicable to the specific site conditions and accident characteristics.
According to equations (1) and (2), the development of OILl and OIL.2 should calculate the effective dose, the thyroid dose, the smoke plume exposure dose, the ground exposure dose, and the inhalation effective dose.
6 Operational intervention level correction
6.1 General requirements
The initial values are calculated on the basis of a hypothetical accident and meteorological and other environmental conditions and should be corrected accordingly to the actual environmental conditions and monitoring results in the event of an actual accident. OIL3 is not related to the type of accident or meteorological conditions, but only to the shielding factor and the residence factor, and does not need to be corrected, No correction is required.
6.2 OIL1 and OIL2 corrections
OIL1 and OIL.2 can be corrected in the event of a stable nuclear accident situation with continued large releases of radioactive material. Air concentrations of radionuclides and surrounding dose equivalent rates are measured during air sampling.
6.3 OIL4 correction
OIL4 should be recalculated every week during the first month of release of accidental radioactive material to account for changes in sediment composition due to decay, and every subsequent month until decay is no longer the dominant influence.
Appendix A (Normative) Dose Action Levels for Acute Exposure
The dose action levels at which intervention is expected in any case when an organ or tissue is acutely irradiated are listed in Table A.1.
Foreword
1 Scope
2 Normative references
3 Terminology and definitions
4 Purpose of the operational intervention level application
5 Development of operational intervention levels
6 Operational intervention level correction
Appendix A (Normative) Dose Action Levels for Acute Exposure
