of March 30, 2022 No. 36
About approval of regulations and rules on ensuring nuclear and radiation safety
Based on item 4 of article 21 of the Law of the Republic of Belarus of June 18, 2019 No. 198-Z "About radiation safety", the paragraph of the fourth of part three of article 6 of the Law of the Republic of Belarus of July 30, 2008 No. 426-Z "About use of atomic energy", subitem 7.4 of Item 7 of the Regulations on the Ministry of Emergency Situations of the Republic of Belarus approved by the Presidential decree of the Republic of Belarus of December 29, 2006 No. 756, the Ministry of Emergency Situations of the Republic of Belarus DECIDES:
2. Recognize invalid paragraphs two, the fourth and fifth Item 1 of the resolution of the Ministry of Emergency Situations of the Republic of Belarus of December 30, 2006 as No. 72 "About approval of regulatory legal acts in the field of ensuring nuclear safety".
V. I. Sinyavsky
It is approved
Committee for State Security
Ministry of Internal Affairs
Ministry of Health
Ministry of natural resources and protection
Approved by the Resolution of the Ministry of Emergency Situations of the Republic of Belarus of March 30, 2022 No. 36
1. Regulations and rules on ensuring nuclear and radiation safety of "The rule of nuclear safety of subcritical stands" (further – Rules) establish technical requirements to sources of ionizing radiation, radiation objects and safe handling of them regarding requirements to design of subcritical assembly and the systems important for safety of the subcritical stand (further – PKS), including to implementation of the organizational and technical actions aimed at providing nuclear safety of PKS.
2. The departures from requirements of these rules caused by scientific feature and the specifics of the equipment advancing these requirements shall be proved in the report of reasons for safety of PKS.
3. These rules extend to the designed, constructed and operated PKS irrespective of their type, except for electronuclear generators of the neutrons including subcritical reactor installation, external source of neutrons in the form of the accelerator of charged particles and the neutron making target.
4. Nuclear safety of PKS is determined on the basis:
technical implementation of the PKS project;
qualities of production and installation of systems (elements) important for safety of PKS.
5. Nuclear safety of PKS in case of operation is ensured:
fulfillment of requirements of acts of the legislation, including requirements of technical regulatory legal acts, obligatory for observance, in the field of ensuring nuclear and radiation safety, requirements of the PKS project and operational documentation;
qualification and discipline of workers (personnel);
system of the organizational and technical actions preventing effects of possible human errors and unauthorized actions, equipment failures, external impacts of natural and technogenic origin.
6. For the purposes of these rules terms and their determinations in the values established by the Law of the Republic of Belarus "About radiation safety" and the Law of the Republic of Belarus "About use of atomic energy" and also the following terms and their determinations are used:
accident on PKS – violation of normal operation of PKS in case of which there was exit of radioactive materials and (or) ionizing radiation for the borders provided by the project for normal operation in the quantities exceeding the set limits of safe operation, and also characterized by initial event, ways of course and effects;
emergency protection of PKS – the protective security system intended for emergency stop of PKS, including working bodies (further – RO) emergency protection (further – AZ) and the executive mechanisms providing change of their provision or condition;
platoon of RO of management system and protection – change of provision (condition) of RO of management system and protection (further – SUZ) which leads to increase in effective coefficient of reproduction of neutrons (further – Keff) subcritical assembly;
loading devices – transport processing equipment, mechanisms and devices used for loading in active zone of subcritical assembly of nuclear fuel and (or) installation of experimental devices;
source of neutrons external – used on subcritical assembly the device which is letting out neutrons intended for increase in density of flow of neutrons in active zone;
the channel of control – the set of the sensor (sensors), transmission line and means of processing of signal and display of information intended for ensuring control of parameter;
modification (reorganization) of subcritical assembly – the changes of structure or geometry of active zone and (or) reflector of subcritical assembly provided by the PKS project;
stop of PKS – clearing (intensity reduction) of chain nuclear reaction of division in active zone of subcritical assembly by means of RO of the regulator of reactivity (further – RR) or other levers on reactivity (in case of their availability) and (or) by removal from active zone of external source of neutrons (normal stop) or owing to operation of AZ (emergency stop);
refusal – the violation of operability of systems (elements) found visually or control facilities and diagnosings (visible refusal) or revealed only when carrying out maintenance (the hidden refusal);
subcritical assembly – complex for experimental studying of the circle which is making multiple copies neutrons which structure and geometry in case of normal operation provide Keff <1;
PKS – the nuclear installation including subcritical assembly and complex of rooms, systems, experimental devices, which is located within the platform determined by the project;
the mode of temporary stop – the mode of operation of PKS consisting in work on maintenance of PKS and preparation of pilot studies;
the mode of long stop – the mode of operation of PKS consisting in work on preservation of the PKS separate systems and their maintenance in operating state during time when conducting pilot studies is not planned for PKS;
the mode of final stop – the mode of operation of PKS consisting in work on preparation of PKS for conclusion from operation including unloading of nuclear fuel from active zone of subcritical assembly and removal of nuclear fuel and other nuclear materials from the PKS platform;
the start-up mode – the mode of operation of PKS in case of which intensity of chain nuclear reaction of division, necessary for pilot studies, with increase Keff of subcritical assembly and (or) use of external source of neutrons is provided;
SUSA – the set of elements of managing systems of normal operation, AZ PKS and managing security system intended for control and management of intensity of chain nuclear reaction of division and also for normal and emergency stop of PKS;
physical start-up of PKS – the stage of input of PKS in operation including loading of nuclear fuel in active zone, achievement of the value established in the PKS project Keff of subcritical assembly and carrying out research of neutron physical characteristics of subcritical assembly for the purpose of experimental confirmation of safety of PKS;
nuclear accident on PKS – the accident on PKS caused by violation of control and management of intensity of chain nuclear reaction of division, formation of critical mass in active zone of subcritical assembly or in case of the treatment of nuclear materials out of subcritical assembly;
nuclear safety of PKS – PKS property to prevent nuclear accidents on PKS and to limit their effects;
nuclear-dangerous works on PKS – works which can lead to nuclear accident in case of violation of limits and (or) conditions of safe operation in case of their accomplishment.
7. The systems and elements important for safety of PKS shall be designed taking into account mechanical, chemical and other internal impacts, possible in case of normal operation and in case of violations of normal operation, including project accidents, and also external impacts of natural and technogenic origin.
8. Shall be provided in the project or operational documentation of PKS:
lists of the settlement programs used for forecasting of neutron physical characteristics of subcritical assembly and reasons for nuclear safety of PKS;
Keff for all conditions of active zone provided in the PKS project with assessment of the error characteristic of the used calculation methods, and taking into account the uncertainty brought by possible technology variations of parameters of the completing elements of active zone and reflector of subcritical assembly from nominal rates;
the maximum effective coefficient of reproduction of neutrons (further – Keffmakh);
the reactivity effects including caused by use of experimental devices and filling of subcritical assembly with water (decelerator);
efficiency of RO SUZ and other levers on reactivity in case of their use;
conditions of ensuring nuclear safety in case of the treatment of nuclear materials out of subcritical assembly;
assessment of effects of possible nuclear accidents, including the accident caused by realization Keffmakh;
the list of nuclear-dangerous works on PKS in case of operation of PKS and action for ensuring nuclear safety of PKS in case of their carrying out.
9. The technical solutions used in the PKS project shall provide:
portion loading (overload) of nuclear fuel in active zone of subcritical assembly and if necessary the portion gulf (discharge) of liquid in case of its use;
subcriticality of subcritical assembly of PKS in the mode of temporary stop at least 2% (Keff <0,98) without the negative reactivity brought by RO AZ;
subcriticality of subcritical assembly of PKS in the mode of long stop at least 5% (Keff <0,95);
safety of PKS in case of any initial event of project accidents with imposing of one refusal, independent of initial event, or one human error, independent of initial event;
safety and working capacity in the conditions of project accidents of the technical means used for registration and storage of information necessary for accident investigation.
10. In the project of again constructed PKS hardware and methodical and metrological support of experimental measurement Keff of subcritical assembly shall be determined.
11. The design of subcritical assembly shall exclude:
the scope changes and the configurations of active zone and (or) reflector leading to increase Keff which are not provided by the project;
possibility of unauthorized movement of its nodes and details;
its conclusion in critical condition because of reduction of leakage of neutrons from active zone in case of approach to it processing equipment or personnel;
unauthorized platoon (emission) of RO SUZ and experimental devices;
jamming and inadvertent unhooking of RO SUZ with the RO executive mechanisms of SUZ.
12. In the PKS project the analysis of reaction of design of subcritical assembly to possible internal and external impacts of natural or technogenic origin, possible refusals or defects for the purpose of identification of possible violations of limits and (or) conditions of safe operation shall be carried out, at the same time the most probable and dangerous refusals and their possible effects shall be determined.
13. As a part of subcritical assembly the external (starting) source of neutrons which intensity shall be chosen so that introduction of this source in subcritical assembly was followed by increase in indications of devices of channels of control of density of flow of neutrons twice at least shall be provided.
14. In the PKS project for the fuel elements (the heat-generating assemblies) of different enrichment, the fuel elements (the heat-generating assemblies) differing in nuclide structure, absorbers of neutrons the corresponding marking (distinctive marks) shall be provided.
15. In the PKS project the possibility of flooding of the room of subcritical assembly shall be analyzed by water. If flooding of the room is not excluded and Keff of subcritical assembly leads to increase, then the room shall be equipped with signaling device of emergence of water and the device for its automatic removal in case of operation of signaling device of emergence of water.
16. As a part of managing systems of normal operation the part of SUZ providing control and management of intensity of nuclear chain reaction of division shall be provided. The specified part of SUZ shall include:
device of remote movement of external source of neutrons;
at least two channels of control of density of flow of neutrons independent among themselves with the showing devices, at the same time, at least, as a part of one channel of control the possibility of record of change of level of density of flow of neutrons of subcritical assembly shall be provided in time;
management systems the RO executive mechanisms of SUZ (in case of their use), remotely moved loading and experimental devices;
channels of control of technology parameters.
17. The range of control of density of flow of neutrons managing system of normal operation shall block all range of change of density of flow of neutrons of subcritical assembly established by the PKS project.
In case of splitting the range of control of density of flow of neutrons into several subranges overlapping of the subranges at least within one decade shall be provided.
18. Sound indication of intensity of chain nuclear reaction of division in subcritical assembly shall be provided in the PKS project. Signals of the sound indicator shall be well heard in rooms of subcritical assembly and Item (panel) of management of PKS.
19. In need of structure of SUZ PO PP used for management of subcriticality level (coefficient of multiplication of neutrons) of subcritical assembly can be provided.
20. The PO PP executive mechanisms shall have indexes of intermediate position and indexes of final provisions.
21. Remotely moved loading and experimental devices shall have limit switches and if necessary indexes of intermediate position.
22. In the PKS project lists shall be brought and proved:
controlled technology parameters and signals of condition of PKS;
regulated parameters and managing signals;
blocking and protection of the equipment with indication of conditions of their operation;
settings and conditions of operation of the precautionary and alarm system.
23. Managing systems of normal operation shall develop, at least, the following signals on the control panel:
precautionary (light and sound) – in case of approach of parameters of subcritical assembly to settings of operation of AZ. Parameter values of subcritical assembly in case of which there is development of warning signals shall be proved in the PKS project;
index – SUZ informing on provision RO and availability of tension in chains of electric utility service of SUZ.
24. The possibility of check of operability of light and sound alarm systems shall be provided in the PKS project.
25. Designs of the PO PP executive mechanisms and other levers on reactivity of subcritical assembly and management system them shall exclude possibility of spontaneous change of provision (condition) of levers on reactivity towards its increase taking into account short circuits, loss of quality of isolation, falls and aimings of tension, other losses or hindrances.
26. In the PKS project test conditions, replacement and conclusion in repair of the PO PP executive mechanisms and other levers to reactivity shall be determined and proved.
27. Managing systems of normal operation shall exclude:
input of positive reactivity (with speed of its change in beff/c) units of measure with speed above beff 0,07 / with;
input of positive reactivity by movement of PO PP, loading or experimental devices if RO AZ are not cocked (in case of their availability);
input of positive reactivity levers on reactivity in case of lack of electric utility service in chains of indexes of intermediate position of the body influencing reactivity in chains of the alarm and precautionary system, in chains of limit switches of experimental or loading devices;
remote increase in reactivity along with two and more workplaces, two and more persons.
28. Managing systems of normal operation shall provide for PO PP with efficiency of more 0,7 of beff and experimental and loading devices efficiency of more 0,3 of beff step input of positive reactivity (step movement) with speed of no more 0,03 of beff / with and the size of step no more 0,3 beff.
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