GB 15146.2-2008Nuclear criticality safety for fissile materials outside reactors - Part 2: Basic technical practices and subcritical limits for handling, processing and operations with fissile materials (English PDF)

Foreword

All technical content in this section is mandatory. GB 15146 "Nuclear criticality safety for fissile materials outside reactor" has so far released the following 11 sections.

--- GB 15146.1 Part 1. Nuclear Criticality Safety Administration regulations (instead of GB 15146.1-1994)

--- GB 15146.2 - Part 2. Operation fissile material, processing and handling of basic technical rules and subcritical limits (instead of GB 15146.2-1994)

--- GB 15146.3 Part 3. storage of fissile material for nuclear criticality safety requirements (instead of GB 15146.3-1994)

--- Aqueous solutions of fissile material for nuclear criticality safety criteria for steel - pipe intersections containing GB 15146.4

--- GB 15146.5 plutonium - natural uranium nuclear criticality control criteria and subcritical limits for mixtures

--- GB/T 15146.6 borosilicate glass Raschig rings and its application criteria

--- GB 15146.7 subcritical neutron multiplication measurements in situ

--- GB 15146.8 Part 8. heap outside the handling, storage and transport of nuclear criticality safety criteria for LWR fuel elements (instead of GB 15146.8-1994)

--- GB 15146.9 performance and testing requirements for nuclear criticality detection and alarm systems

--- GB 15146.10 Safety requirements for fixed neutron absorber

--- GB/T 15146.11 based nuclear criticality safety limits and controls moderator This section GB Part of 215,146. This Part replaces GB 15146.2-1994 "for fissile materials outside reactor - Nuclear criticality safety for fissile materials operations, processing, handling, The basic technical criteria and subcritical limits. " Compared with GB 15146.2-1994 part of the main changes are as follows:

--- Increasing the foreword and Appendix C (informative);

--- The "Verify calculation method" (1994 edition) to "confirm the calculation method" (Chapter 5 edition), and increased general requirements;

1 Scope

Part 2 is the technical core of the criticality safety series: the basic practices and the subcritical limits for handling and processing fissile material. It gives the single-parameter and multi-parameter limits - mass, dimension, concentration, volume, moderation, reflection and interaction - that keep an operation subcritical, together with the requirements on the calculational methods used to justify a limit, on the validation of the computer codes and nuclear data behind them, and on confirming a subcritical configuration in practice. It is the document a criticality safety engineer works from. Issued on 19 September 2008, in force since 1 August 2009, replacing GB 15146.2-1994. This page is published from the official record of the standard held by the Chinese standards administration: the identification, the dates, the classification and the edition it replaces are taken from there. The clause text, the tables and the numeric limits are not reproduced on this page - they are in the document itself, which is delivered in full in English translation.

GB 15146 of the provisions of this part of fissile materials outside reactor operation, processing and handling of basic technical rules and some geometry Subcritical limits simple fissile material monomers, and the establishment of nuclear criticality safety evaluation validity and scope of the proposed method of calculation Requirements. The basic requirements for nuclear criticality safety administration see GB 15146.1. This section applies to fissile materials outside reactor operation, processing and handling. This section does not apply to fissile material under controlled conditions of assembly operations (such as a critical test).

2 Normative references

The following documents contain provisions which, through reference in this text, constitute provisions of this part. For dated references, subsequent Amendments (not including errata content) or revisions do not apply to this section, however, encourage the parties to this part of the research agreement Whether the latest versions of these documents. For undated reference documents, the latest versions apply to this section.

GB 15146.5 outside reactors Yi Nuclear criticality safety plutonium fissile material - nuclear criticality control criteria and subcritical natural uranium mixtures Limit

3 Terms and Definitions

The following terms and definitions apply to this part of GB 15146.

3.1 Physically, the total number of neutrons produced within a certain time interval (excluding fission neutron source intensity is not a function of the rate generated Child) with the same time interval internal absorption and leakage loss ratio of the total number of neutrons.

3.2 Energy self-sustaining or divergent neutron chain reaction accident caused by the release event.

3.3 Criticality accident prevention and mitigation of the consequences of criticality accidents in which the most important is to prevent such accidents.

3.4 So that the numerical parameters maintained within the prescribed limits of.

3.5 A controlled parameters specified under specified conditions to make sure the system is limiting value subcritical state. This parameter limits contained Margin of uncertainty that will remain as it is used when you export the calculation results and the experimental data, but does not include accident response (such as double batch feeding, like Product margin analysis results are incorrect, etc.) require.

3.6 The vertical projection of the total mass per unit area in the plane of fissile material. For infinite uniform flat surface density equal to the thickness of the plate Degree within the plate fissile material density of the product.

3.7 The results provide a computer program, including mathematical equations, approximation, assuming the relevant numerical parameters (such as cross-sectional data) and the like.

3.8 The method of calculation between calculation results with the experimental data, a measure of systematic differences.

3.9 The calculation results of a measurement of the accuracy and precision of both the experimental data and uncertainty.

3.10 Material component, geometric arrangement, neutron energy spectrum and other relevant parameters (such as non-uniformity, leakage, interaction, absorption, etc.) defined range Wai, calculated in this (or these) range of the method of bias have been identified.

4 Basic Technical Regulations

4.1 General Requirements Effective multiplication factor of the system (k eff) is dependent on the quality of all fissile material and other related materials, distribution and nuclear properties. One or more parameters of the system should be controlled within subcritical limits, and stay out of subcriticality margin in response to process accident Amount to achieve nuclear criticality safety. You can use the following methods to control the parameters of the system.

a) physical limitations, e.g., limited within the solution not greater than the diameter of the cylindrical container a predetermined value;

b) monitoring and control equipment, for example, can use to measure the concentration and preventing fissile nuclides in chemical systems in gathering equipment, fissile nuclides The concentration is maintained at a predetermined value or less;

c) chemical means, for example, to prevent the emergence of conditions can cause the precipitation of the aqueous solution to maintain the concentration of its unique features;

d) natural or credible course of events, for example, rely on the inherent characteristics of the process, so that the density of uranium oxide is always less than the theoretical density Some of the provisions of the share;

e) administrative procedures, for example, the quality requirements of the operating fissile material does not exceed the posted limit;

4.2 controlled parameter It should be clear that all controlled parameters and their limits. We should clearly understand the impact of changes in these parameters on the system of k eff.

4.3 pairs accident principle Process design should contain a sufficient safety factor, making it necessary to be occur in a variety of conditions related to at least two unlikely , Independent of changes, it may lead to a critical accident.

4.4 Geometry Control Whenever possible, it is desirable to rely on limiting device geometry design rather than administrative measures to implement the critical control. Equipment design When geometry, can take advantage of the characteristics of nuclear materials and technology equipment. Before starting the operation should be run to verify all depend on the implementation of the provisional Geometry and characteristics of the nuclear industry control, and shall take appropriate measures so that they can be maintained.

4.5 Application of neutron absorber You can use the neutron absorbing material (such as cadmium and boron) added to the process equipment or materials or means to implement both among the critical control. It shall take appropriate measures so that the neutron absorbing material is added continued to maintain its intended distribution and concentration. Neutron absorber solution When, in particular, should take effective control measures.

4.6 subcritical limits of determination As long as a suitable experimental data, it should be based on experimental data to establish the subcritical limits, and should consider the use of inaccurate data Given the appropriate degree of left margin. In the absence of direct use of experimental data can be derived from the calculation times provisional boundaries Value, but the calculation method used should be in accordance with the provisions of Chapter 5, by comparison with experimental data proved valid. Claim

5 Calculation Method

5.1 General Requirements There are many suitable calculation method to determine the system of sub-critical state. They are based on a variety of forms and, for the field of nuclear criticality safety Different circumstances which apply to a broad range of value is not the same, therefore, the calculation method used for nuclear criticality safety evaluation, whether by According to how the form, in accordance with provisions of this chapter shall first establish the validity and scope of the system being evaluated.

5.2 bias determined 1) 1) No test data are available, it is impossible to determine the bias calculation method, making it impossible to meet the requirements of 5.2. By other terms and calculation methods Comparison of calculation results to confirm the calculation method is unacceptable. Calculation method should determine bias, bias should be determined by establishing the critical test data with the corresponding experimental system between the calculated result Relationship to (see Appendix B). Typically, you should use the calculated value k eff under critical state experimental system for the calculation and experimental results Correlation between the results in this case, the bias value is calculated k eff with respect to the deviation of 1. You can also take advantage of the physical state and other parameters, to establish the correlation between the experimental data and calculation results between the corresponding experimental system to determine Bias calculation method. It should be used to bias the computation method standardization within its scope of application, making it possible to predict the critical strip within the limits of bias Uncertainty Member. Bias and uncertainty is usually not constant, both of which may be a function of composition and other variables.

5.3 bias tends to extend the scope of application Scope calculation method can be extended to the area outside the experimental conditions, provided that within the scope of the use of experimental conditions tend to bias It has been determined that the deflection region. Large regional expansion, should be supplemented by other calculation methods, so that the extended region bias (esp Which is a bias uncertainty) estimates more reliable and consistent proof of the results. Uncertainty subcritical margin of

5.4 degree of bias Uncertainty of bias should cover corresponding to the following Uncertainty k eff (or other parameters) of the amount of deductions, these packages uncertainty Including the uncertainty of experimental conditions, calculation methods lack accuracy and precision, the scope expansion introduced uncertainty and so on. Determine the accuracy and precision and deduct an amount corresponding to the bias and uncertainty corresponds to the calculation method later, you should k eff (or He related parameters) to impose appropriate criticality margin times; the allowance should be large enough to ensure that the case by this method calculated in virtually certain It is subcritical; and bias and uncertainty as to the margin may change with composition and other variables (see Appendix B and Appendix C). Check

5.5 computer program The calculation method is included in a computer program, it should be verified to confirm the mathematical operation is carried out as intended. For computer programs Order was amended, should be re-verified.

5.6 kernel parameters Nuclear characteristic parameter calculation method used (such as cross-sectional data) should be consistent with its experimental results.

5.7 confirmation report You should prepare a written confirmation reports. This report should.

a) the method of calculation in sufficient detail to make clear and precise description so that others can independently reproduce the results;

b) specify the method of calculation used to confirm the experimental data, and lists the parameters derived from the experimental data;

c) description of the scope of application of the calculation method;

d) Description of bias and subcriticality margin within the scope of application and demonstration of subcritical margin determined is appropriate.

6 Fissile nuclides single parameter limits

6.1 Application limits - General requirements 6.2,6.3,6.4,

6.6 lists some of the fissile nuclides isolated monomers single parameter limits, they are made to meet the Chapter

5 Calculation requirements calculated. If these limits conditions are met, then a limit to comply with any of them, fissile material Operation, handling and processing can be performed safely. Only when it can be proved that the material monomers around (including near other fissile material) make When increasing the effective multiplication factor (k eff) is not greater than tightly wrapped infinitely thick layer of water so that the monomer increase k eff, said limits allowed applications. When a limit is applied to the above mixture of fissile nuclides should be the mixture of each fissile nuclide having deemed The kind of radionuclide minimum limit to consider. It should be emphasized that the process specification must leave appropriate criticality margin times to cope with uncertainty and limits of process variables is accidentally exceed.

6.2 homogeneous aqueous solution Maintaining a uniform aqueous premise, i.e., to maintain the concentration of the aqueous solution does not exceed the value of the saturated solution, in Table 1 can be any of a limit value To use. If the concentration of plutonium -240 greater than the concentration of plutonium-241, and in the calculation of the mass or concentration of plutonium-241 as plutonium-239, plutonium-239 is Limits may also be used a mixture of various plutonium isotopes. (For a mixture of plutonium isotopes plutonium -240 considerable case

7.4 Some of the more lenient provisions limit). Atomic ratio limits and concentration limits are equivalent, but the former is also applicable to non-aqueous solution, and Regardless of the chemical form of the fissile nuclides.

6.3 aqueous mixture The areal density limits in Table 1 can be used for fissile material having any chemical composition. In the areal density is uniform under the premise, with their The mixture has a density gradient is also effective. For subcritical mass may not be uniform mixture, uranium-233, uranium-235 and plutonium-239 Limits were 0.50kg, 0.70kg and 0.45kg, and has nothing to do with the chemical composition. Table 1 fissile nuclides homogeneous aqueous solution of a single parameter limits parameter Subcritical limits 233UO2F2 233UO2 (NO3) 2 235UO2F2 235UO2 (NO3) 2 239Pu (NO3)