BS 5915-1980 Specification for equipment for minehead assay and sorting radioactive ores in containers《矿车种放射性矿石矿井口检定和分选规范》.pdf

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1、BRITISH STANDARD BS 5915:1980 IEC 600:1979 Specification for Equipment for minehead assay and sorting radioactive ores in containers UDC 621.039 791.2:622.349.5:622.725:539.16 + 669.9BS5915:1980 This British Standard, having been prepared under the directionof the Nuclear Engineering Standards Commi

2、ttee, was published underthe authority of the Executive Board and comes intoeffect on 31March1980 BSI 12-1999 The following BSI references relate to the work on this standard: Committee reference NCE/4 Draft for comment 77/80384 DC ISBN 0 580 11227 6 Cooperating organizations The Nuclear Engineering

3、 Standards Committee, under whose direction this British Standard was prepared, consist of representatives from the following Government department and scientific and industrial organizations: Association of Consulting Engineers British Electrical and Allied Manufacturers Association (BEAMA) British

4、 Insurance (Atomic Energy) Committee Electricity Supply Industry in England and Wales* Health and Safety Executive* Lloyds Register of Shipping National Radiological Protection Board* Radiochemical Centre* Scientific Instrument Manufacturers Association* The Institution of Nuclear Engineers* United

5、Kingdom Atomic Energy Authority* Water-tube Boilermakers Association The organizations marked with an asterisk in the above list, together with the following, were directly represented on the committee entrusted with the preparation of this British Standard: Association of X-ray Equipment Manufactur

6、ers British Institute of Non-destructive Testing British Institute of Radiology Clinical Physics and Bioengineering Electronic Engineering Association Institute of Physics Amendments issued since publication Amd. No. Date of issue CommentsBS5915:1980 BSI 12-1999 i Contents Page Cooperating organizat

7、ions Inside front cover National foreword ii Section 1. General 1 Scope 1 2 Object 1 3 General description of operation 1 4 Description of equipment 2 5 Definitions 2 Section 2. Technical characteristics 6 General 2 7 Detectors 2 8 Installation conditions 3 9 Measuring procedure 3 Section 3. Rated o

8、perating conditions 10 Temperature 3 11 Humidity 3 12 Barometric pressures 4 13 Power supply 4 14 Environmental tests 4 Section 4. Safety requirements 15 General 4 16 Protective device for accessible parts of live conductors (excluding safetyextra-low voltage) 4 17 Marking 5 Section 5. Characteristi

9、cs to be specified in the instruction manual 18 General 5 19 General characteristics 5 20 Power supply 5 21 Performance characteristics 5 National appendix A IEC Standard frequencies (IEC Publication 196) 6 National appendix B Classification of electrical and electronic equipmentwithregard to protec

10、tion against electric shock (IECPublication 536) 6 Publications referred to Inside back coverBS5915:1980 ii BSI 12-1999 National foreword This British Standard is identical with IEC Publication600 “Equipment for minehead assay and sorting radioactive ores in containers” published by the Internationa

11、l Electrotechnical Commission (IEC). The standard has been prepared under the direction of the Nuclear Engineering Standards Committee, and the UK took part in the work of IEC Technical Committee45 that prepared IEC600. The formal decisions or agreements of the IEC on technical matters, prepared by

12、Technical Committees on which all the National Committees having a special interest therein are represented, express, as nearly as possible, an international consensus of opinion on the subjects dealt with. They have the form of recommendations for international use, and they are accepted by the Nat

13、ional Committees in that sense. Terminology and conventions. The text of the International Standard hasbeen approved as suitable for publication, without deviation, as a BritishStandard. Some terminology and certain conventions are not identical with those used in British Standards. The references t

14、o IEC196:1965 and IEC536:1976, for which there are no corresponding British Standards, contain mandatory requirements, and are therefore reproduced asNational appendix A andNational appendix B respectively to this standard. A British Standard does not purport to include all the necessary provisions

15、of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Cross-references International Standard Corresponding British Standard IEC 38:1975 BS 77:1958 Voltages for a.c. trans

16、mission and distribution systems (Technically equivalent) IEC 68-2 BS 2011 Basic environmental testing procedures Part 2.1 Tests (Identical) IEC 278:1968 BS 4308:1968 Documents supplied with electronic measuring instruments (Technically equivalent) IEC 529:1976 BS 5490:1977 Specification for degrees

17、 of protection provided by enclosures (Identical) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages1 to 8, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will

18、 be indicated in the amendment table on the inside front cover.BS5915:1980 BSI 12-1999 1 Section 1. General 1 Scope This standard is applicable to equipment for grading and sorting radioactive ores in containers at minehead and in open-cast workings, described in Clauses3 and4. 2 Object a) To lay do

19、wn mandatory requirements. b) To give a list of characteristics which the manufacturer shall specify in the instruction manual supplied with each apparatus (see IEC Publication278, Documentation to be Supplied with Electronic Measuring Apparatus). 3 General description of operation 3.1 Such equipmen

20、t, used at the minehead or in open-cast workings and quarries, ensures two functions: a) Estimation of the grade of uranium ore, permitting the sampling of exploratory work and the survey of the production output. As the measured gamma radioactivity does not directly represent the content of uranium

21、 metal, the processing of the results is made using a statistical method, establishing the correlation between radioactivity and uranium content. This allows account to be taken of the state of the radioactive equilibrium of the ore. b) Selection of the quarried products, which enables avoidance of

22、unnecessary freight and processing charges for ore with a uranium content that is too low to be economical to process, and also allows classification of ores into several ranges of uranium contents, so that each grade may be treated appropriately. 3.2 The starting of the measuring cycle is controlle

23、d either manually or automatically, by the skip displacement, or by the placing of a truck; a cycle includes, for example: a) Measurement: determining the product radioactivity by means of a scaler during a predetermined time interval. b) Selection: at the end of the measurement, the information on

24、the grade of the product (sterile, poor ore, mixed ore, rich ore) is transmitted to the sorting device. c) Recording: the measurement results are transmitted to a printing or perforating machine the number of the general location, the number of the measurement, the radioactivity, the designation of

25、the special location displayed on landing at the skip terminal, the class of ore, and optionally, the ore mass. d) Verification of the background: after removal of the product or departure of the truck, a background measurement allows survey of probe operation, product removal and local contaminatio

26、n. When commissioning the plant, it is necessary to carry out a background measurement replacing the sample material by an equal amount of material with as low a radioactivity as possible, e.g.river sand, to simulate the absorption of background radiation by the mineral. e) Background recording. f)

27、End of the cycle. 3.3 According to use at the minehead or in open-cast workings, equipment belongs to two classes: a) Cylinder sorting equipment used at the minehead. Usually, in order to carry out the measurement in a container easy of access and easily decontaminated, and in order not to hinder mi

28、ning, each skip tips its load into a cylinder in which measurement is made while the skip performs a new quarrying cycle. Measurement can also be made directly on the skip or on trams previously separated in order to avoid mutual influence. b) Sorting equipment for trucks used in open-cast workings

29、and quarries. The trucks to be measured and sorted stop under an archway which supports the detector, which is high enough to eliminate geometrical variations and collimated to “see” only ore, excluding ground area which is usually contaminated.BS5915:1980 2 BSI 12-1999 Operating conditions, particu

30、larly in regard to geometry, call for different types of detectors for these two classes of equipment (generally Geiger-Mller counter tubes for sorters for cylinders and scintillation detectors for sorters for trucks). Special care shall be taken in the design of sorters for trucks, which are normal

31、ly used in the open air and therefore can be subject to large variations in temperature and other severe environmental conditions. 4 Description of equipment Equipment for rapid analysis and sorting include: one or more detectors (usually Geiger-Mller counter tubes or scintillation detectors) design

32、ed to detect the gamma radiation emitted by the truck or cylinder load. The detector housing may contain the high-voltage supply, temperature conditioning devices and the pre-amplifier. The housing may also include shields against ionizing radiation and radiation filters to eliminate the lower energ

33、y part of the spectrum, which is subject to perturbation matrix effects. the associated electronics which includes power supply, signal shaping, discrimination and possibly selection devices (with single-channel or multi-channel analyzers, ratemeter, timebase). recording and storage devices (compute

34、r, printing machine, typewriter, etc.). devices for signalling or for actuating electromechanisms which switch ores according to their grade classes to various storage bins or areas. 5 Definitions 5.1 cylinder a cylindrical compartment in which ore is retained for measurement 5.2 sterile ore with a

35、uranium content too low to be economical to process Section 2. Technical characteristics 6 General The instrument shall be capable of estimating the uranium content of the ore from the measurement of the emitted gamma radiation (less background). It therefore, when directly giving a value of the con

36、tent, shall use an activity-content correlation in the form: log t u= K log A + C where: which allows the taking into account of such factors as radioactive equilibrium state. The K coefficient and the constant C, which are characteristic of the particular deposit being worked, are established after

37、 sampling and fed to the instrument before measuring. Simpler devices indicate only the radioactivity and require calculation, or use of graphs or tables, for determining the corresponding content. As the results are usually given in digital form, this standard does not give any requirements concern

38、ing analogue apparatus. 7 Detectors The detectors generally used are Geiger-Mller counter tubes or scintillation detectors. t u = uranium content A = activityBS5915:1980 BSI 12-1999 3 Scintillation detectors offer the advantage of higher detection efficiency for all gamma ray energies above15keV. Th

39、is higher efficiency for low energies may cause inaccurate assays because of self-absorption (varying with the effective atomic number Z eq ) in the product, thus calling for radiation filtering. Scintillation detectors are also more affected by changes in temperature. Geiger-Mller counter tubes off

40、er a lower detection efficiency, but are less affected by changes in temperature and the lower efficiency for lower gamma ray energies reduces the effect of the products effective atomic number (Z eq ). In addition, their better response to higher energies permits detecting radiation originating fro

41、m greater depths within the ore container. Also, they offer the additional advantages of being more rugged and having a simpler electrical circuit. 8 Installation conditions 8.1 Detectors shall be protected against ambient ionizing radiation and particularly against its variations. The effect of bac

42、kground radiation can be reduced through shielding and collimation of the detectors. The measurement area shall consist of an inactive concrete slab. In sorting equipment for trucks, the detector height and the collimator position shall be adjusted so that the angle of view corresponds to the truck

43、contents. The detector shall be placed high enough to prevent the variation in the truck loading introducing variations in the measurement greater than5%. 8.2 The equipment may be completed by the following devices: a device to determine the quantity of contained uranium, which possibly elaborates t

44、he production balance per shift, per day, per month; an emergency system which stops the operation of the installation when the sorting equipment is faulty. 9 Measuring procedure Unless otherwise required the counting time shall be between30s and1min. Unless otherwise required the full measurement c

45、ycle should not exceed2min. The number of recorded events during the measurement shall lead to a variation coefficient equal to or less than5% for a content of300 parts per million of uranium at equilibrium state, which is currently considered as low in economic terms. This content corresponds appro

46、ximately to the boundary content between payable ore and sterile (some of these steriles, however, can be treated on site by leaching). In the rated temperature range, the mean of the counting shall not vary by more than5%. The fractional counting loss shall be less than10%, under the rated range of

47、 use, for the maximum rated content, usually10%. When scintillation detectors are used, the electronic threshold shall correspond to an energy of30keV, so as to minimize the effect of temperature changes; when the filtration of lower energies is required, it shall be made by a suitable radiation fil

48、ter. Section 3. Rated operating conditions 10 Temperature a) Detection sub-assemblies: 25 C to+50 C. NOTEThe materials of many photomultiplier tubes do not permit their continuous use above+50 C. b) Associated electronics: 0 C to+40 C. When equipment is used under more extreme temperature conditions

49、, it shall be provided with a conditioning system. 11 Humidity 10% to95%.BS5915:1980 4 BSI 12-1999 12 Barometric pressures 70kPa to106kPa for use up to2200m. In the case of use at a higher altitude, special requirements shall be established. 13 Power supply Instruments shall be able to be supplied from the mains according to IEC Publications38, IEC Standard Voltages, and196, IEC Standard Frequencies. Instruments shall accept any variations within: 10% of the nominal voltage. 2% of the nominal frequency. If the instruments are to be used on an i