A method for formulating the operation intervention level of pressurized water reactor nuclear power units

Abstract

The present invention relates to a method for formulating an operation intervention level of a pressurized water reactor nuclear power unit, comprising: (1) confirming the intervention level of an OIL category OILa; (2) for a certain type of severe accident b of the nuclear power unit, using its release source term to calculate the value of OILa at the time t after the shutdown; (3) for multiple time points of t≤T, repeating step (2), obtaining the numerical calculation result of OILa of the severe accident b within the time 0 to T after the shutdown, and drawing a change curve; (4) for all severe accidents, repeating step (3), obtaining the OILa change curve of all severe accidents within 0 to T, taking the minimum envelope value as the calculation result of OILa; (5) for all OIL categories, repeating steps (1)-(4), obtaining an OIL calculation result set. The method couples IAEA-EPR-NPP-OILs with my country's national standard GB18871-2002, not only including the most advanced technical concepts in the world, but also conforming to my country's current standards, and can provide support for emergency preparedness and response of pressurized water reactor nuclear power plants.

Description

Technical Field

[0001] The invention belongs to nuclear facility emergency preparedness and response design technology, and specifically relates to a method for formulating an operation intervention level of a pressurized water reactor nuclear power unit. Background Art

[0002] The nuclear emergency plan is the last link in the principle of defense in depth for nuclear safety and is of great significance to the safety of the public around nuclear facilities. The operational intervention level (OIL) is one of the important contents in the formulation of the emergency plan. According to my country's nuclear safety guidelines "Emergency Preparedness and Emergency Response of Nuclear Power Plant Operating Units" (HAD002 / 01-2019), the emergency plan must include the OIL established for this nuclear power plant and its revision method. In addition, technical documents related to the formulation of the OIL must be submitted before the first loading.

[0003] The concept of OIL was first proposed by the International Atomic Energy Agency (IAEA) in the 1990s. The technical document "General Analytical Procedure for Determining Protective Actions During Reactor Accidents" (IAEA-TECDOC-955, 1997) describes the basic methods and recommended values ​​for the formulation of OIL, which has been used in my country to this day. In recent years, especially after learning from the emergency response experience of the Fukushima nuclear accident, the IAEA has continuously improved and upgraded the system, types and formulation of OIL, and finally formed the technical document "Operational Intervention Levels for Reactor Emergencies and Methodology for Their Derivation" (IAEA-EPR-NPP-OILs, 2017). However, since this document uses the "General Criteria (GC)" described in IAEA's "Safety Standards Series" GSR Part 7 in the calculation of the recommended value of OIL, it is different from the nuclear accident emergency intervention principles and intervention levels in my country's current mandatory national standard "Basic Standard for Ionizing Radiation Protection and Radiation Source Safety" (GB18871-2002), so it has not yet been put into practical use. Summary of the invention

[0004] The purpose of the present invention is to couple IAEA-EPR-NPP-OILs with my country's national standard GB18871-2002, and provide a method for formulating the operation intervention level of a pressurized water reactor nuclear power unit, which can be directly applied to the formulation and optimization of the operation intervention level of a pressurized water reactor nuclear power unit.

[0005] The technical solution of the present invention is as follows: A method for formulating an operation intervention level of a pressurized water reactor nuclear power unit comprises the following steps:

[0006] (1) Based on the operational intervention level OIL classification in IAEA-EPR-NPP-OILs, one of the OIL categories OILa is confirmed to have its intervention level in accordance with GB18871-2002 “Basic Standards for Protection against Ionizing Radiation and Safety of Radiation Sources”;

[0007] (2) For a certain type of severe accident b of the nuclear power unit, use its release source term to calculate the value of OILa at time t after shutdown. A type b severe accident refers to an accident that may cause a large amount of radioactivity to be released into the environment;

[0008] (3) Repeat step (2) for multiple time points t≤T, where T is the applicable time of OILa, obtain the numerical calculation results of OILa for severe accident b within the time 0 to T after shutdown, and draw a change curve;

[0009] (4) Repeat step (3) for all severe accidents of nuclear power units to obtain the OILa variation curves of all severe accidents within 0 to T, with the minimum envelope value being the calculation result of OILa;

[0010] (5) Repeat steps (1) to (4) for all OIL categories to obtain the OIL calculation result set.

[0011] Furthermore, in the method for formulating the operational intervention level of a pressurized water reactor nuclear power unit as described above, in step (2), when OILa is OIL1γ of the OIL classification in IAEA-EPR-NPP-OILs, the calculation formula is as follows:

[0012]

[0013] Where:

[0014] t——The time after the reactor is shut down, in seconds (s);

[0015] RA i (t,mix)——the relative activity of nuclide i released from the core to all released products at time t after the reactor is shut down, dimensionless;

[0016] UC——Unit conversion factor from Sv / s to μSv / h, specifically 3.6E+09;

[0017] H* grd-sh,i ——Conversion factor of ambient dose equivalent rate at 1 meter above the ground, in units of [(Sv / s) / (Bq / m 2 )]; IAEA recommends the product of the ground deposited external radiation effective dose conversion factor, the ground roughness calibration factor of 0.7, and the effective dose and ambient dose equivalent conversion factor of 1.4 (for the photon energy of concern);

[0018] WFOIL1γ - Weighting factor, used to avoid inappropriate response actions based on the OIL1γ setting value, the IAEA recommended value is 3;

[0019] GC (Urgent, E, 7d) - The intervention level determined according to GB18871-2002 "Basic Standard for Ionizing Radiation Protection and Radiation Source Safety", with an expected dose of 50mSv in 7 days;

[0020] E grd-scenario (7d) – for the “ground” scenario, the total effective dose to the representative person from the ground activity concentration of nuclide i over 7 days, in units of [Sv / (Bq / m 2 )], taking into account the corresponding exposure pathways.

[0021] Furthermore, in the method for formulating the operational intervention level of a pressurized water reactor nuclear power unit as described above, in step (2), when OILa is OIL2γ of the OIL classification in IAEA-EPR-NPP-OILs, the calculation formula is as follows:

[0022]

[0023] Where:

[0024] t——The time after the reactor is shut down, in seconds (s);

[0025] RA i (t,mix)——the relative activity of nuclide i released from the core to all released products at time t after the reactor is shut down, dimensionless;

[0026] UC——Unit conversion factor from Sv / s to μSv / h, specifically 3.6E+09;

[0027] H* grd-sh,i ——Conversion factor of ambient dose equivalent rate at 1 meter above the ground, in units of [(Sv / s) / (Bq / m 2 )]; IAEA recommends the product of the ground deposited external radiation effective dose conversion factor, the ground roughness calibration factor of 0.7, and the effective dose and ambient dose equivalent conversion factor of 1.4 (for the photon energy of concern);

[0028] WF OIL2γ - Weighting factor, used to avoid inappropriate response actions based on the OIL2γ setting value, the IAEA recommended value is 1;

[0029] GC (Urgent, E, 1m) - The intervention level determined according to GB18871-2002 "Basic Standard for Ionizing Radiation Protection and Radiation Source Safety", with an expected dose of 30mSv per month;

[0030] Egrd-scenario (1m) – for the “ground” scenario, the total effective dose to the representative person from the ground activity concentration of nuclide i over a period of 1 month, in units of [Sv / (Bq / m 2 )], taking into account the corresponding exposure pathways.

[0031] Furthermore, in the method for formulating the operational intervention level of a pressurized water reactor nuclear power unit as described above, in step (2), when OILa is OIL4γ of the OIL classification in IAEA-EPR-NPP-OILs, the calculation formula is as follows:

[0032]

[0033] Where:

[0034] t——The time after the reactor is shut down, in seconds (s);

[0035] RA i (t,mix)——the relative activity of nuclide i released from the core to all released products at time t after the reactor is shut down, dimensionless;

[0036] UC——Unit conversion factor from Sv / s to μSv / h, specifically 3.6E+09;

[0037] H* skin-100cm 2 -srf,i ——The activity per unit area of ​​radionuclide i at a distance of 100 cm 2 The ambient dose equivalent rate at 10 cm from the skin surface is expressed in [(Sv / s) / (Bq / m 2 )];

[0038] WF OIL4 - Weighting factor, used to avoid inappropriate response actions according to the default value of OIL4γ, the IAEA recommended value is 0.5;

[0039] e ing,skin-scenario,i - In the "skin" scenario, the activity concentration of radionuclide i on the skin surface causes the accumulated effective dose to a representative person due to unintentional ingestion, in units of [Sv / (Bq / m 2 )];

[0040] GC (Urgent, E, 7d) - The intervention level determined according to GB18871-2002 "Basic Standard for Ionizing Radiation Protection and Radiation Source Safety", with an expected dose of 50mSv in 7 days;

[0041] GC (Acute, AD skin-ext,10h) - General criteria for equivalent action levels for acute exposure of red bone marrow, used to take emergency response actions based on the RBE-weighted absorbed dose to the skin within 10 hours, 10 Gy / 100 cm 2 ;

[0042] ad skin,skin-scenario,i ——In the “skin” scenario, the RBE-weighted absorbed dose to the dermis from the activity concentration of radionuclide i on the skin surface, in units of [Gy / (Bq / m 2 )].

[0043] Further, in the method for formulating the operational intervention level of a pressurized water reactor nuclear power unit as described above, in step (2), when OILa is OIL4β of the OIL classification in IAEA-EPR-NPP-OILs, the calculation formula is as follows:

[0044]

[0045] Where:

[0046] t——The time after the reactor is shut down, in seconds (s);

[0047] RA i (t,mix)——the relative activity of nuclide i released from the core to all released products at time t after the reactor is shut down, dimensionless;

[0048] R 4π,β,i (baseline-inst) – the ideal response factor of a baseline beta monitor, reflecting the response per nuclear transformation per second [Bq] [cps] of radionuclide i on the surface, expressed in (cps / Bq);

[0049] WF OIL4 - Weight factor, used to avoid inappropriate response actions according to the default value of OIL4β, the IAEA recommended value is 0.5;

[0050] R eff,β (baseline-inst)——is the effective window area of ​​the baseline beta monitor, specifically 1.5E-03m 2 ;

[0051] CorF field,β ——is the field p calibration factor for the beta monitor, accounting for the attenuation caused by measuring under field (i.e. non-ideal) conditions, specifically 0.25;

[0052] GC (Urgent, E, 7d) - The intervention level determined according to GB18871-2002 "Basic Standard for Ionizing Radiation Protection and Radiation Source Safety", with an expected dose of 50mSv in 7 days;

[0053] GC (Acute, AD skin-ext ,10h) is a general criterion for the equivalent of the acute irradiation dose action level for red bone marrow, used to take emergency response actions in any environment based on the RBE-weighted absorbed dose to the skin within 10 hours, 10Gy / 100cm 2 ;

[0054] e ing,skin-scenario,i - In the "skin" scenario, the activity concentration of radionuclide i on the skin surface causes the committed effective dose to a representative person due to unintentional ingestion, in units of [Sv / (Bq / m 2 )];

[0055] ad skin,skin-scenario,i ——In the “skin” scenario, the RBE-weighted absorbed dose to the dermis from the activity concentration of radionuclide i on the skin surface, in units of [Gy / (Bq / m 2 )].

[0056] Furthermore, in the above-mentioned method for formulating the operation intervention level of a pressurized water reactor nuclear power unit, in step (2), when OILa is OIL7 of the OIL classification in IAEA-EPR-NPP-OILs, the calculation formula is as follows:

[0057]

[0058] Where:

[0059] t——The time after the reactor is shut down, in seconds (s);

[0060] RA Cs-137 (t,mix)——the relative activity of the nuclide Cs-137 released from the core to all released products at time t after the reactor is shut down, dimensionless;

[0061] RA i (t,mix)——the relative activity of nuclide i released from the core to all released products at time t after the reactor is shut down, dimensionless;

[0062] WF OIL7 - Weight factor, used to avoid inappropriate corresponding actions according to the value set by OIL7, the IAEA takes the default value of 5;

[0063] GC (Ingestion, ing,1a)——Represents the general criteria for the accumulated effective dose caused by ingestion of food, milk or drinking water, which is basically equivalent to the international food standard "General Standard for Contaminants and Toxins in Food and Feed" (CODEXSTAN 193-1995, revised in 2016), which lists the guidance values ​​of various radionuclides in food and the general action level of food in GB18871-2002 "Basic Standard for Protection against Ionizing Radiation and Safety of Radiation Sources", 0.01Sv in the first year;

[0064] e food-post-analysis-scenario,i - In the post-food analysis scenario, the unit activity of radionuclide i in food, milk or drinking water represents the committed effective dose to a person from one year's ingestion.

[0065] Further, in the method for formulating the operation intervention level of a pressurized water reactor nuclear power unit as described above, in step (2), when OILa is OIL8γ of the OIL classification in IAEA-EPR-NPP-OILs, the calculation formula is as follows:

[0066]

[0067] Where:

[0068] t m ——The time from the uptake of radionuclides by the thyroid gland to the measurement, in seconds (s);

[0069] - The conversion factor of the ambient dose equivalent rate per unit I-I3I (stock) activity of the thyroid gland measured in front of the thyroid gland using the baseline monitoring of the thyroid gland close to the neck, the specific value is 2.9E-14, the unit is [(Sv / s) / Bq];

[0070] WF OIL8γ - Weight factor, the IAEA recommends a value of 1 to avoid inappropriate response actions according to the OIL8γ default value;

[0071] UC——Unit conversion factor from Sv / s to μSv / h, specifically 3.6E+09;

[0072] GC (Urgent, h thyroid,thy-burden )——Adopt the intervention level of taking stable iodine GC (Urgent, D thyroid ), which is conservatively converted to the committed equivalent dose of radioactive iodine in the thyroid gland (thyroid stock) to the thyroid gland, 100 mGy ≈ 0.1 Sv;

[0073] h thyroid,I-131-thyoid-burden - the conversion factor of I-131 in the thyroid gland (thyroid stock) to the committed equivalent dose to the thyroid gland;

[0074] λ I-131 ——Decay constant of I-131, unit S -1 ;

[0075] λ bio-I-131 ——The biological removal constant of I-131 in the thyroid gland is 1.0E-7, and the unit is S -1 .

[0076] Furthermore, in the method for formulating the operational intervention level of a pressurized water reactor nuclear power unit as described above, in step (2), when OILa is OIL3γ of the OIL classification in the IAEA-EPR-NPP-OILs, OIL5 described in the IAEA-TECDOC-955 report can be used as a substitute and set to 1μSv / h, which is significantly higher than the natural background level of radioactivity in the environment (about 100nSv / h).

[0077] The beneficial effects of the present invention are as follows: the present invention couples IAEA-EPR-NPP-OILs with my country's national standard GB18871-2002 to construct a method for formulating the operation intervention level of a pressurized water reactor nuclear power unit. The method not only includes the most advanced technical concepts in the world, but also complies with my country's current standards, and can provide support for emergency preparedness and response of pressurized water reactor nuclear power plants, so that my country's pressurized water reactor nuclear power units in service, under construction and planned to be built have higher safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Figure 1 A flow chart of a method for formulating an operational intervention level for a pressurized water reactor nuclear power unit according to the present invention;

[0079] Figure 2 It is a curve diagram of the change of OIL1γ of a nuclear power unit with the time after shutdown in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0080] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0081] like Figure 1 As shown, a method for formulating an operation intervention level of a pressurized water reactor nuclear power unit provided by the present invention comprises the following steps:

[0082] (1) Based on the OIL classification of operational intervention levels in IAEA-EPR-NPP-OILs, for a certain OIL category OILa, confirm its intervention level according to Table 1;

[0083] Table 1 lists the OIL classification and intervention level in a method for formulating the operation intervention level of a pressurized water reactor nuclear power unit. The various OIL intervention levels and corresponding emergency actions listed in the table are based on GB18871-2002 "Basic Standard for Ionizing Radiation Protection and Radiation Source Safety".

[0084] (2) For a certain type of severe accident b among the Class B severe accidents of nuclear power units, its release source term is used to calculate the value of OILa at time t after shutdown. Class B severe accidents include all accidents that may cause a large amount of radioactivity to be released to the environment, such as the design extension conditions of core melting, secondary probabilistic safety analysis accidents, etc. t should be less than the applicable time T of OILa, as shown in Table 1. Since "standard people" are used to represent people in nuclear accident consequence assessment and emergency response in my country, it is necessary to adjust the calculation formula of OIL in IAEA-EPR-NPP-OILs, which are:

[0085] OIL1γ:

[0086]

[0087] Where:

[0088] t——The time after the reactor is shut down, in seconds (s);

[0089] RA i (t,mix)——the relative activity of nuclide i released from the core to all released products at time t after the reactor is shut down, dimensionless;

[0090] UC——Unit conversion factor from Sv / s to μSv / h, specifically 3.6E+09;

[0091] H* grd-sh,i ——Conversion factor of ambient dose equivalent rate at 1 meter above the ground, in units of [(Sv / s) / (Bq / m 2 )]; IAEA recommends the product of the ground deposited external radiation effective dose conversion factor, the ground roughness calibration factor of 0.7, and the effective dose and ambient dose equivalent conversion factor of 1.4 (for the photon energy of concern);

[0092] WF OIL1γ - Weighting factor, used to avoid inappropriate response actions based on the OIL1γ setting value, the IAEA recommended value is 3;

[0093] GC (Urgent, E, 7d)—intervention levels listed in Table 1, with an expected dose of 50 mSv for 7 days;

[0094] E grd-scenario(7d) – for the “ground” scenario, the total effective dose to the representative person from the ground activity concentration of nuclide i over 7 days, in units of [Sv / (Bq / m 2 )], considering the exposure pathways listed in Table 1.

[0095] OIL2γ:

[0096]

[0097] Where:

[0098] WF OIL2γ - Weighting factor, used to avoid inappropriate response actions based on the OIL2γ setting value, the IAEA recommended value is 1;

[0099] GC (Urgent, E, 1m)—intervention levels listed in Table 1, with an expected dose of 30 mSv in 1 month;

[0100] E grd-scenario (1m) – for the “ground” scenario, the total effective dose to the representative person from the ground activity concentration of nuclide i over a period of 1 month, in units of [Sv / (Bq / m 2 )], considering the exposure pathways listed in Table 1;

[0101] Other parameters are the same as OIL1γ.

[0102] OIL4γ:

[0103]

[0104] Where:

[0105] H* skin-100cm 2 -srf,i ——The activity per unit area of ​​radionuclide i at a distance of 100 cm 2 The ambient dose equivalent rate at 10 cm from the skin surface is expressed in [(Sv / s) / (Bq / m 2 )];

[0106] WF OIL4 - Weighting factor, used to avoid inappropriate response actions according to the default value of OIL4γ, the IAEA recommended value is 0.5;

[0107] e ing,skin-scenario,i - In the "skin" scenario, the activity concentration of radionuclide i on the skin surface causes the accumulated effective dose to a representative person due to unintentional ingestion, in units of [Sv / (Bq / m 2 )];

[0108] GC (Acute, AD skin-ext,10h) - General criteria for equivalent action levels for acute exposure of red bone marrow, used to take emergency response actions based on the RBE-weighted absorbed dose to the skin within 10 hours, 10 Gy / 100 cm 2 ;

[0109] ad skin,skin-scenario,i ——In the “skin” scenario, the RBE-weighted absorbed dose to the dermis from the activity concentration of radionuclide i on the skin surface, in units of [Gy / (Bq / m 2 )];

[0110] Other parameters are the same as OIL1γ.

[0111] OIL4β:

[0112]

[0113] Where:

[0114] R 4π,β,i (baseline-inst) – the ideal response factor of a baseline beta monitor, reflecting the response per nuclear transformation per second [Bq] [cps] of radionuclide i on the surface, expressed in (cps / Bq);

[0115] R eff,β (baseline-inst)——The effective window area of ​​the baseline beta monitor, specifically 1.5E-03m 2 ;

[0116] CorF field,β - The field p calibration factor for the beta monitor, which accounts for the attenuation caused by measuring under field (i.e. non-ideal) conditions, is specifically 0.25.

[0117] Other parameters are the same as OIL4γ.

[0118] OIL7:

[0119]

[0120] Where:

[0121] RA Cs-137 (t,mix)——the relative activity of the nuclide Cs-137 released from the core to all released products at time t after the reactor is shut down, dimensionless;

[0122] WF OIL7 - Weight factor, used to avoid inappropriate corresponding actions according to the value set by OIL7, the IAEA takes the default value of 5;

[0123] e food-post-analysis-scenario,i- the committed effective dose from one year's ingestion of the unit activity of radionuclide i in food, milk or drinking water in the scenario after food analysis, in [Sv / (Bq / kg)];

[0124] GC (Ingestion, eing, 1a) - represents the general criteria for the accumulated effective dose caused by ingestion of food, milk or drinking water, which is basically equivalent to the international food standard "General Standard for Contaminants and Toxins in Food and Feed" (CODEXSTAN 193-1995, revised in 2016), which lists the guidance values ​​of various radionuclides in food and the general action level of food in GB18871-2002 "Basic Standard for Protection against Ionizing Radiation and Safety of Radiation Sources", 0.01Sv in the first year;

[0125] Other parameters are the same as OIL1γ.

[0126] OIL8γ:

[0127]

[0128] Where:

[0129] t m ——The time between the uptake of radionuclides by the thyroid gland and the measurement, in seconds (s).

[0130] - The conversion factor of the ambient dose equivalent rate per unit I-I3I (stock) activity of the thyroid gland measured in front of the thyroid gland using the baseline monitoring of the thyroid gland close to the neck, the specific value is 2.9E-14, the unit is [(Sv / s) / Bq];

[0131] WF OIL8γ - Weight factor, the IAEA recommends a value of 1 to avoid inappropriate response actions according to the OIL8γ default value;

[0132] UC——Unit conversion factor from Sv / s to μSv / h, specifically 3.6E+09;

[0133] GC (Urgent, h thyroid,thy-burden )——Adopt the intervention level of taking stable iodine GC (Urgent, D thyroid ), which is conservatively converted to the committed equivalent dose to the thyroid gland based on the radioactive iodine in the thyroid gland (thyroid accumulation), 100 mGy ≈ 0.1 Sv;

[0134] h thyroid,I-131-thyoid-burden - the conversion factor of I-131 in the thyroid gland (thyroid stock) to the committed equivalent dose to the thyroid gland;

[0135] λ I-131——Decay constant of I-131, unit S -1 ;

[0136] λ bio-I-131 ——The biological removal constant of I-131 in the thyroid gland is 1.0E-7, and the unit is S -1 .

[0137] OIL3γ:

[0138] For OIL3γ, OIL5 described in the IAEA-TECDOC-955 report can be used as a substitute, and it can be simply set to 1μSv / h, which is significantly higher than the natural background level of radioactivity in the environment (about 100nSv / h).

[0139] (3) Repeat step (2) for multiple time points t≤T, where T is the applicable time of OILa, obtain the numerical calculation results of OILa for severe accident b within the time 0 to T after shutdown, and draw a change curve;

[0140] (4) Repeat step (3) for all Class B severe accidents of nuclear power units to obtain the OILa variation curve of Class B severe accidents within 0-T, with the minimum envelope value as the calculation result of OILa;

[0141] (5) Repeat steps (1) to (4) for all OIL categories to obtain the OIL calculation result set.

[0142] Example

[0143] Assume that for a certain pressurized water reactor nuclear power unit, the operational intervention level is formulated:

[0144] (1) For OIL1γ, according to Table 1, the intervention level was confirmed as: 7-day expected dose 50 mSv;

[0145] (2) The applicable time of OIL1γ is a few days after the accident release begins. For a certain severe accident of the unit, based on its release source term, the value of OIL1γ at 0.1 day after shutdown is calculated using the following formula:

[0146]

[0147] Where:

[0148] RA i (0.1d, mix) – the relative activity of the nuclide i released from the core to all released products 0.1 day after the reactor was shut down;

[0149] H* grd-sh,i ——Conversion factor of ambient dose equivalent rate at 1 meter above the ground, in units of [(Sv / s) / (Bq / m 2)]; IAEA recommends the product of the ground deposited external radiation effective dose conversion factor, the ground roughness calibration factor of 0.7, and the effective dose and ambient dose equivalent conversion factor of 1.4 (for the photon energy of concern);

[0150] E grd-scenario (7d) – for the “ground” scenario, the total effective dose to the representative person from the ground activity concentration of nuclide i over 7 days, in units of [Sv / (Bq / m 2 )], considering the exposure pathways listed in Table 1;

[0151] (3) The applicable time of OIL1γ is within a few days after the accident release begins; repeat step (2) for many time points within a few days after the accident release begins, such as 0.2 days, 0.3 days, 0.4 days...6.9 days, 7 days, etc., obtain the values ​​of OIL1γ at these time points, and draw a curve of the change relative to the time after the shutdown;

[0152] (4) For other serious accidents, including the design extension condition of core melt, the Level 2 probabilistic safety analysis accident and all other accidents that may cause a large amount of radioactivity to be released into the environment, repeat step (3) to obtain the value of OIL1γ at each time point; Figure 2 This is a curve chart showing the variation of OIL1γ of the nuclear power unit with the time after shutdown, taking the accident source term of the secondary probabilistic safety analysis as an example. It can be seen that the minimum envelope value is 2000μSv / h, which is the calculation result of OIL1γ.

[0153] (5) Repeat steps (1) to (4) for OIL2γ, OIL4γ, OIL4β, OIL7 and OIL8γ to obtain their respective minimum envelope values, which are the OIL result set.

[0154] Table 1 OIL classification and intervention level of a method for formulating the operation intervention level of a PWR nuclear power unit

[0155]

[0156]

[0157] a. In emergency preparedness, the expected dose is used as the preventable dose.

[0158] b. When contaminated food accounts for 0.1 of the number of major consumer foods, the general action level for food protection in GB18871-2002 is approximately equivalent to the annual effective dose to the public of 1 mSv; if all consumer foods are considered to come from contaminated areas, the general action level for food protection in GB18871-2002 is approximately equal to the effective dose by ingestion of 10 mSv / a.

[0159] c. Since the acute expected absorbed dose to the red bone marrow within 2 days cannot be represented by monitoring data, the 2-day irradiation is conservatively compressed to 10 hours. According to IAEA GSR Part 7, the skin surface absorbed dose rate of 10 Gy can be used as the representation of decontamination.

[0160] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0161] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for formulating an operation intervention level for a pressurized water reactor nuclear power unit, characterized in that: The steps include: (1) Based on the operational intervention level OIL classification in IAEA-EPR-NPP-OILs, one of the OIL categories OILa is confirmed to have its intervention level in accordance with GB18871-2002 “Basic Standards for Protection against Ionizing Radiation and Safety of Radiation Sources”; (2) For a certain type of severe accident b among all severe accidents of nuclear power units, use its release source term to calculate the value of OILa at time t after shutdown. A type b severe accident refers to an accident that may cause a large amount of radioactivity to be released into the environment; (3) Repeat step (2) for multiple time points t≤T, where T is the applicable time of OILa, obtain the numerical calculation results of OILa for severe accident b within the time 0 to T after shutdown, and draw a change curve; (4) Repeat step (3) for all severe accidents of nuclear power units to obtain the OILa variation curves of all severe accidents within 0 to T, with the minimum envelope value being the calculation result of OILa; (5) Repeat steps (1) to (4) for all OIL categories to obtain the OIL calculation result set.

2. The method for formulating the operation intervention level of a pressurized water reactor nuclear power unit according to claim 1, characterized in that: In step (2), when OILa is OIL1γ classified in the IAEA-EPR-NPP-OILs, the calculation formula is as follows: Where: t——time after reactor shutdown; RA i (t,mix)——the relative activity of nuclide i released from the core to all released products at time t after the reactor is shut down; UC - unit conversion factor from Sv / s to μSv / h; H* grd-sh,i - conversion factor for ambient dose equivalent rate at 1 meter above the ground; WF OIL1γ - weighting factor, used to avoid inappropriate response actions according to the OIL1γ setting value; GC (Urgent, E, 7d) - The intervention level determined according to GB18871-2002 "Basic Standard for Ionizing Radiation Protection and Radiation Source Safety", with an expected dose of 50mSv in 7 days; E grd-scenario (7d) – for the "ground" scenario, the total effective dose to a representative person from the ground activity concentration of nuclide i over 7 days.

3. The method for formulating the operation intervention level of a pressurized water reactor nuclear power unit according to claim 1, characterized in that: In step (2), when OILa is OIL2γ classified in the IAEA-EPR-NPP-OILs, the calculation formula is as follows: Where: t——time after reactor shutdown; RA i (t,mix)——the relative activity of nuclide i released from the core to all released products at time t after the reactor is shut down; UC - unit conversion factor from Sv / s to μSv / h; H* grd-sh,i - conversion factor for ambient dose equivalent rate at 1 meter above the ground; WF OIL2γ — weighting factor, used to avoid inappropriate response actions based on the OIL2γ setting; GC (Urgent, E, 1m) - The intervention level determined according to GB18871-2002 "Basic Standard for Ionizing Radiation Protection and Radiation Source Safety", with an expected dose of 30mSv per month; E grd-scenario (1m) – For the "ground" scenario, the total effective dose to a representative person from the ground activity concentration of nuclide i over a period of 1 month.

4. The method for formulating the operation intervention level of a pressurized water reactor nuclear power unit according to claim 1, characterized in that: In step (2), when OILa is OIL4γ classified in the IAEA-EPR-NPP-OILs, the calculation formula is as follows: Where: t——time after reactor shutdown; RA i (t,mix)——the relative activity of nuclide i released from the core to all released products at time t after the reactor is shut down; UC - unit conversion factor from Sv / s to μSv / h; H* skin-100cm 2 -srf,i ——The activity per unit area of ​​radionuclide i at a distance of 100 cm 2 The ambient dose equivalent rate at 10 cm from the skin surface; WF OIL4 - weighting factor, used to avoid inappropriate response actions according to the OIL4γ default value; e ing,skin-scenario,i - in the "skin" scenario, the activity concentration of radionuclide i on the skin surface resulting in the committed effective dose to a representative person from unintentional ingestion; GC (Urgent, E, 7d) - The intervention level determined according to GB18871-2002 "Basic Standard for Ionizing Radiation Protection and Radiation Source Safety", with an expected dose of 50mSv in 7 days; GC (Acute, AD skin-ext ,10h) - General criteria for equivalent action levels for acute exposure of red bone marrow, used to take emergency response actions based on the RBE-weighted absorbed dose to the skin within 10 hours, 10 Gy / 100 cm 2 ; ad skin,skin-scenario,i - In the "skin" scenario, the RBE-weighted absorbed dose to the skin dermis due to the activity concentration of radionuclide i on the skin surface.

5. The method for formulating the operation intervention level of a pressurized water reactor nuclear power unit according to claim 1, characterized in that: In step (2), when OILa is OIL4β classified in the IAEA-EPR-NPP-OILs, the calculation formula is as follows: Where: t——time after reactor shutdown; RA i (t,mix)——the relative activity of nuclide i released from the core to all released products at time t after the reactor is shut down; R 4π,β,i (baseline-inst) – the ideal response factor of a baseline beta monitor, reflecting the response to radionuclide i per nuclear transformation per second [Bq] [cps] on the surface; WF OIL4 - weighting factor, used to avoid inappropriate response actions according to the default value of OIL4β; R eff,β (baseline-inst)——effective window area of ​​the baseline beta monitor; CorF field,β - Field p calibration factor for beta monitors; GC (Urgent, E, 7d) - The intervention level determined according to GB18871-2002 "Basic Standard for Ionizing Radiation Protection and Radiation Source Safety", with an expected dose of 50mSv in 7 days; GC (Acute, AD skin-ext , 10h) - General criteria for equivalence of action levels for acute exposure of red bone marrow, used to take emergency response actions based on the RBE-weighted absorbed dose to the skin within 10 hours in any environment; e ing,skin-scenario,i - in the "skin" scenario, the activity concentration of radionuclide i on the skin surface resulting in the committed effective dose to a representative person from unintentional ingestion; ad skin,skin-scenario,i - In the "skin" scenario, the RBE-weighted absorbed dose to the skin dermis due to the activity concentration of radionuclide i on the skin surface.

6. The method for formulating the operation intervention level of a pressurized water reactor nuclear power unit according to claim 1, characterized in that: In step (2), when OILa is OIL7 of the OIL classification in IAEA-EPR-NPP-OILs, the calculation formula is as follows: Where: t——time after reactor shutdown; RA Cs-137 (t,mix)——the relative activity of the nuclide Cs-137 released from the core to all released products at time t after the reactor is shut down; RA i (t,mix)——the relative activity of nuclide i released from the core to all released products at time t after the reactor is shut down; WF OIL7 - weighting factors to avoid inappropriate corresponding actions according to the OIL7 setting value; GC (Ingestion, eing, 1a) - represents the general criteria for the accumulated effective dose caused by ingestion of food, milk or drinking water, which is basically equivalent to the international food standard "General Standard for Contaminants and Toxins in Food and Feed" which lists the guidance values ​​of various radionuclides in food and the general action level for food in GB18871-2002 "Basic Standard for Protection against Ionizing Radiation and Safety of Radiation Sources", 0.01Sv in the first year; e food-post-analysis-scenario,i - In the post-food analysis scenario, the unit activity of radionuclide i in food, milk or drinking water represents the committed effective dose to a person from one year's ingestion.

7. The method for formulating the operation intervention level of a pressurized water reactor nuclear power unit according to claim 1, characterized in that: In step (2), when OILa is OIL8γ classified in IAEA-EPR-NPP-OILs, the calculation formula is as follows: Where: t m - the time between the uptake of the radionuclide by the thyroid gland and the measurement; - the conversion factor for the ambient dose equivalent rate per unit I-I3I (stock) activity of the thyroid gland measured in front of the thyroid gland using the baseline monitor of the thyroid gland close to the neck; WF OIL8γ - weighting factor, used to avoid inappropriate response actions according to the OIL8γ default value; UC - unit conversion factor from Sv / s to μSv / h; GC (Urgent, h thyroid,thy-burden )——Adopt the intervention level of taking stable iodine GC (Urgent, D thyroid ), which is conservatively converted to the committed equivalent dose of radioiodine to the thyroid gland; h thyroid,I-131-thyoid-burden - conversion factor for the committed equivalent dose of I-131 to the thyroid gland; λ I-131 ——decay constant of I-131; λ bio-I-131 ——Bioremoval constant for I-131 from thyroid gland.

8. The method for formulating the operation intervention level of a pressurized water reactor nuclear power unit according to claim 1, characterized in that: In step (2), when OILa is OIL3γ in the OIL classification of IAEA-EPR-NPP-OILs, OIL5 described in the IAEA-TECDOC-955 report can be used as a substitute, and is set to 1 μSv / h, which is significantly higher than the natural background level of radioactivity in the environment.

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