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1、BRITISH STANDARD BS 5552:1978 IEC 568:1977 Code of practice for In-core instrumentation for neutron fluence rate (flux) measurements in power reactors UDC 621.039.564.2:539.16.074 Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 13:58:44 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5552:1978
2、This British Standard, having been prepared under the direction of the Nuclear Engineering Standards Committee, was published under the authority of the Executive Board on 30 June 1978 BSI 02-2000 The following BSI references relate to the work on this standard: Committee reference NCE/8 Draft for c
3、omment 75/41656 ISBN 0 580 10204 1 Cooperating organizations The Nuclear Engineering Standards Committee, under whose direction this British Standard was prepared, consists of representatives from the following scientific and industrial organizations: Association of Consulting Engineers* British Ele
4、ctrical and Allied Manufacturers Association (BEAMA) British Insurance (Atomic Energy) Committee Electricity Supply Industry in England and Wales* Health and Safety Executive* Hevac Association Institution of Mechanical Engineers Lloyds Register of Shipping National Radiological Protection Board* Sc
5、ientific Instrument Manufacturers Association* The Institution of Nuclear Engineers* United 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 entrus
6、ted with the preparation of this British Standard: Association of University Protection Officers British Industrial Measuring and Control Apparatus Manufacturers Association British Institute of Radiology British Nuclear Forum British Steel Industry Business Equipment Trade Association Control and A
7、utomation Manufacturers Association (BEAMA) Electronic Engineering Association Hospital Physicists Association Ministry of Defence Society for Radiological Protection Individual companies Amendments issued since publication Amd. No.Date of issueComments Licensed Copy: sheffieldun sheffieldun, na, Fr
8、i Dec 01 13:58:44 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5552:1978 BSI 02-2000i Contents Page Cooperating organizationsInside front cover National forewordii 1Scope and object1 2Definitions1 3General considerations2 4System design: general requirements3 5In-core (on-line) neutron detectors: g
9、eneral requirements4 6Mechanical characteristics4 7Electrical and nuclear characteristics4 8Range of operating conditions5 9Prototype testing5 10Production testing6 11Testing of system before operation6 Publications referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01
10、13:58:44 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5552:1978 ii BSI 02-2000 National foreword This British Standard is identical with IEC 568:1977 “In-core instrumentation for neutron fluence rate (flux) measurements in power reactors” and it is published under the direction of the Nuclear Engin
11、eering Standards Committee. The United Kingdom has taken part in the preparation of this International Standard by Subcommittee 45A of Technical Committee No. 45 of the International Electrotechnical Commission (IEC). The formal decisions or agreements of IEC on technical matters, prepared by techni
12、cal 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 national c
13、ommittees in that sense. Terminology. The text of the International Standard has been accepted as suitable for publication, without alteration. Certain terminology is not identical with that used in British Standards; attention is especially drawn to the following. Wherever the word “standard” appea
14、rs, referring to this publication, it should be interpreted as “British Standard”. Cross references. For each of the following references to International Standards given in the text, there is a corresponding British Standard; these are as listed below: NOTE 1The reference to IEC 231B:1972 “Second s
15、upplement. Principles of instrumentation of direct cycle boiling water power reactors”, for which there is no corresponding British Standard, constitutes informative matter only, and since no mandatory requirements are involved, the validity of this British Standard is not affected. NOTE 2After cons
16、ultation with the responsible committee, approval has been given to the adoption of IEC 515:1975 “Radiation detectors for the instrumentation and protection of nuclear reactors; characteristics and test methods” as a dual-numbered British Standard. A British Standard does not purport to include all
17、the necessary provisions 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. International StandardCorresponding British Standard IEC 231:1967 IEC 231A:1969 (includes cl
18、ause 5: Protection system clause 8: General alarms) BS 4877:1972 Recommendation for general principles of nuclear Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 6, an inside back cover and a back cover. This standard has been updated (see co
19、pyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 13:58:44 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5552:1978 BSI 02-20001 1 Scope and object This standard appli
20、es to in-core (on-line) neutron detectors and instrumentation which is designed for safety, information or control purposes. It also applies to components in so far as these components are contained within the primary envelope of the reactor. The detector types usually used are d.c. ionization chamb
21、ers, fission ion chambers and self-powered neutron detectors. This standard is intended as a code of practice for the design of in-core instrumentation for neutron fluence rate measurements in thermal neutron reactors designed for power production. The major emphasis in this guide is on the general
22、design aspect of on-line systems. NOTEFor the principles of overall system design and purpose of neutron flux measurements, reference should be made to IEC Publication 231, General Principles of Nuclear Reactor Instrumentation, Clause 2. 2 Definitions For the purposes of this standard, the following
23、 definitions are applicable: 2.1 sensitivity (of a detector) the sensitivity of a detector to the radiation to be measured is given by: in most applications, the detector is linear and has a negligible output signal for zero input hence: 2.2 sensitive material (of a neutron detector) the material us
24、ed in certain neutron detectors, either, for example, in a lining or a filling gas, which is intended to produce directly ionizing particles from the neutrons by nuclear reaction (I.E.V. 391-06-03) 2.3 burn-up life (of a neutron detector) an estimated fluence of neutrons of a given energy distributi
25、on after which the sensitive material will be consumed to such an extent that the detector characteristics exceed the specified tolerances for a specified purpose (I.E.V. 391-10-11) 2.4 useful life (of a neutron detector) operational life, under irradiation and environmental conditions restricted wi
26、thin specified limits, after which the detector characteristics exceed the specified tolerances. Useful life can be expressed in incident particle fluence, number of produced pulses, etc. (I.E.V. 391-10-10) 2.5 in-core neutron detector a detector, fixed or movable, designed for the measurement of ne
27、utron fluence rate (flux) or neutron fluence at a defined point or in a region of a reactor core or primary envelope 2.6 primary envelope an enclosure of high integrity containing the fuel and the primary coolant (IEC Publication 231B) 2.7 power density thermal power developed per unit volume in the
28、 core of a reactor S variation of the output quantity (deetctor response) variation of the input quantity (radiation to be measured) - -= sensitivity S output quantity (deetctor response) input quantity (radiation to be measured) - -= Licensed Copy: sheffieldun sheffieldun, na, Fri Dec 01 13:58:44 G
29、MT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5552:1978 2 BSI 02-2000 2.8 off-line neutron detector a detector the output signal of which is not available for readout until the detector has been removed from the measuring position. The part subjected to neutron exposure may be in the form of a gas or
30、 fluid of defined volume or in a solid form as a wire, a set of balls, etc. after exposure, the neutron-induced radioactivity of that part is measured at a different location by suitable means 2.9 on-line neutron detector a detector which produces an electrical signal representative of the neutron f
31、luence rate while it is in the measuring position 2.10 perturbed neutron fluence rate (flux) mean neutron fluence rate at a location with the neutron detector placed in the same position for measurement. This quantity is equal to the detector output divided by its true (unperturbed) sensitivity and
32、is practically equal to the neutron fluence rate averaged over the detector surface 2.11 unperturbed neutron fluence rate (flux) mean neutron fluence rate at a location without the neutron detector placed in the same position 3 General considerations 3.1 In a power reactor with a core which has larg
33、e physical dimensions it may be important, for operational reasons, to monitor not only the mean value of the in-core neutron fluence rate (flux) over the whole reactor core but also its spatial distribution. Local measurements at a particular position in the core are often combined with local contr
34、ol functions, the purpose of which is to ensure adequate safety margins for protection system parameters or to provide for optimum utilization of the fuel. Depending on the reactor type, this may be performed on a relative or an absolute basis. 3.2 Measurements of local in-core neutron fluence rate
35、(flux) are in some cases necessary for safety reasons for example, for protecting the fuel from damage caused by local disturbances in the coolant flow or by transients in the local power density. Such abnormal conditions may not be identified with sufficient sensitivity by means of measurements out
36、side the core. In this case, the in-core measuring assemblies are usually connected to the reactor protection system. 3.3 In-core neutron fluence rate (flux) instrumentation may also be used to provide information of a more general nature about the reactor or about component performance. Examples of
37、 information derived from neutron fluence rate data are vibration of in-core components, boiling phenomena in a liquid coolant, total neutron fluence on individual fuel assemblies, etc. 3.4 In some reactors, neutron fluence rate (flux) instrumentation outside the primary envelope cannot be used for
38、start-up and intermediate power operations. Measurement and control of gross reactor power and local power conditions may therefore be provided over part or all of the required range by means of in-core neutron detectors. 3.5 Special in-core instrumentation may be needed to facilitate periodic recal
39、ibration of the neutron fluence rate (flux) instrumentation described in Sub-clauses 3.1 to 3.4 above. Both isotopic activation techniques and movable in-core detectors may be used for this purpose. 3.6 Parts of the in-core instrumentation system may be located in very severe environments. Exposure
40、to high neutron and gamma radiations is liable to cause transformations and structural changes in the materials used and to affect the mechanical and electrical properties of the equipment. Great care shall therefore be taken in the choice of suitable materials. Furthermore, design consideration sha
41、ll, in most cases, be given to the effects of high environmental pressure, pressure cycling, high temperature, temperature gradients and temperature cycling. 3.7 Those parts of the instrumentation system which are installed within the primary envelope of the reactor are usually inaccessible for main
42、tenance or replacement for long periods of time. It is therefore often necessary to provide for adequate system availability by means of redundancy. Detectors may be spatially distributed such that adequate coverage is ensured for a specified acceptable number of failures. Licensed Copy: sheffieldun
43、 sheffieldun, na, Fri Dec 01 13:58:44 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 5552:1978 BSI 02-20003 4 System design: general requirements 4.1 The possible influence of instrumentation intended for in-core installation on the operating characteristics of the reactor shall be carefully evaluate
44、d. In particular, this evaluation shall consider maximum reactivity transients which may be caused by conceivable malfunctioning of the equipment, possible disturbance of the coolant flow in normal and abnormal conditions, any risk that the equipment will disturb the performance of safety actions an
45、d the risk of malfunctions which may cause damage to the primary envelope integrity. The analysis should take account of procedures for replacement of in-core equipments. The procedure which best ensures plant availability should be preferred and it shall not degrade the specific safety requirements
46、. The provision of spare parts or the ability to change the detector with the reactor at power should be considered. 4.2 In cases where in-core instrumentation is used for reactor protection action or is otherwise necessary for safe operation of the reactor, it shall be designed in accordance with t
47、he protection system requirements given in IEC Publications 231 and 231A. 4.3 The in-core parts of the system should contain, as far as possible, only materials which have known acceptable properties in the ambient conditions prevailing in the reactor core. In particular, the influence on pertinent
48、characteristics of long-term neutron and gamma irradiations and temperature cycling should be known, preferably from prototype tests or from interpretation of experimentally obtained data. 4.4 The consequences of equipment failure to the reactor should be taken into account in the choice of in-core
49、components as well as the design of primary envelope penetrations. For example, the insulation materials of in-core cables should not react adversely with the surroundings if the cable sheath is broken. 4.5 The instrumentation system should be designed to facilitate the functional testing, if required, of th