Approved by
Decree of
Gosatomnadzor of Russia
dated December, 31, 2003 No. 9

Effective from
May, 28, 2004

FEDERAL RULES AND REGULATIONS
IN THE AREA OF ATOMIC ENERGY USE

NUCLEAR
SAFETY RULES FOR
 PULSE RESEARCH REACTORS

NP-048-03

This regulatory document establishes the requirements for nuclear safety assurance in the course of design, construction, commissioning and operation of the pulse research reactors.

The document is developed in accordance with the legislation of the Russian Federation with due regard for the requirements of federal regulations and rules as well as the document INTERNATIONAL ATOMIC ENERGY AGENCY, Safety Requirements of the Research Reactors. Draft Safety Requirements to supersede SS 35-S1 and 35-S2, Status: Review CSS, Vienna 2003.

The regulatory document is issued for the first time.

The regulatory document has passed legal examination at the Russian Ministry of Justice (Letter of the Russian Ministry of Justice No. 07/670-UD dated 21.01.2004).

Abbreviations

PRR - Pulse Research Reactor

APRR - Aperiodic Pulse Research Reactor

PPRR - Periodic Pulse Research Reactor

CPS - Control and Protection Systems

FA - Fuel Assembly

CSS - Control Safety Systems

NOCS - Normal Operation Control Systems

Terms and definitions  <*>

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<*> The terms specified in the federal rules and regulations in the area of atomic energy use are applied in these Rules together with the terms included into this section.

The following terms and definitions are used for the purposes of this document.

1. Emergency protection of the PRR:

- the safety function providing for emergency shutdown of the reactor;

- the set of safety systems performing the emergency protection function.

2. Autocatalysis of the chain nuclear fission reaction - power density increase in the PRR power pulse due to changes in the reactor nuclear core introduced by the chain nuclear fission reaction itself.

3. Safe state of the PRR - sub-criticality and state of the PRR systems and equipment established in the design <*> and ensuring the PRR safety in the course of its operation in the temporary shutdown mode.

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<*> In these Rules the term "design" shall mean the package of documentation issued in the course of the PRR design, development and construction as well as technical documentation developed by the operating organization in the course of the PRR operation.

4. Lifting of the CPS control devices - change in the position (state) of the CPS control devices resulting in positive reactivity insertion.

5. Complete sub-criticality of the PRR - the PRR sub-criticality in the long-term shutdown mode preventing transfer of the reactor into the critical state with due regard for any potential common cause failures.

6. Diagnostics - the monitoring function aimed to determine operability of the diagnosed object.

7. Pulse research reactor - the reactor intended to generate power pulses while providing fast neutron super-criticality.

8. Aperiodic pulse research reactor - the reactor where fast neutron super-criticality is suppressed after the power pulse initiation due to the feedback "power (temperature) - reactivity".

9. Periodic pulse research reactor - the reactor where the power pulse is initiated and suppressed with the preset frequency through the use of the reactivity control devices.

10. Monitoring channel - the set consisting of a sensor, communication line and means for signal processing and (or) information display intended to ensure monitoring of the parameter within the scope specified in the design.

11. Set of emergency protection equipment - equipment of the control and protection system performing the functions for the emergency protection state monitoring and the reactor emergency protection control functions within the scope prescribed in the design.

12. Monitoring - part of the control function aimed to assess the parameter value or to define the state (identify) of the controlled process or equipment.

13. Reactivity modulator - the set of the PPRR CPS components ensuring periodic change of reactivity with the preset frequency and amplitude.

14. Independent systems (components) - systems (components) where a failure of any system (component) does not result in a failure of other system (component).

15. Handling of nuclear materials - the activity related to refueling, transportation, storage and any other operations with nuclear materials.

16. PRR shutdown - switching of the PRR from the critical (super-critical) state into the sub-critical state through the use of the CPS control devices and any other reactivity control equipment in case of necessity.

17. Sub-critical state - state of the reactor characterized by the effective neutron multiplication factor value below one.

18. Starter device - the set of the APRR CPS components providing for fast reactivity increase in order to generate a power pulse.

19. CPS control device - a reactivity control device used in the CPS and ensuring reactivity variation through its position (state) changing.

The CPS control devices are divided into the following groups in accordance with their functional purpose:

- emergency protection control devices;

- reactivity compensation control devices (compensating devices);

- manual and automatic adjustment control devices;

- control devices of the APRR starter;

- control devices of the PPRR reactivity modulator.

20. Temporary PRR shutdown mode - the PRR operation mode with the PRR shutdown for a certain period of time in order to perform any works for the PRR maintenance and preparation for experimental research.

21. Long-term shutdown mode - the PRR operation mode with the PRR shutdown in order to perform the works for preservation of individual systems and equipment and maintenance of the PRR operability within the period when no experimental research on the PRR is planned.

22. Final shutdown mode - the PRR operation mode with the PRR shutdown in order to prepare for the PRR decommissioning including unloading of nuclear materials from the nuclear core and their removal from the PRR site.

23. Start-up mode and power operation - the PRR operation mode with the PRR power raising through the use of the CPS control devices and performance of experimental research with the PRR neutrons and ionizing radiation.

24. Interconnected nuclear cores - nuclear cores of a multi-core APRR when the neutron flux density (power) of each nuclear core affects spatial distribution of neutrons in other PRR nuclear cores.

25. Control and protection system - the set of components of normal operation control systems, protective, control and supporting safety systems intended to ensure safe progress and termination of the chain nuclear fission reaction.

26. PRR experimental device - any device or appliance intended to perform experimental research on the PRR (loop channels, beam tubes, ampoules, etc.).

27. Nuclear accident on the PRR - any accident on the PRR caused by:

- any malfunction in monitoring and control of the chain nuclear fission reaction in the reactor nuclear core or exceedance of the rated reactivity (power) pulse parameters;

- criticality occurrence in the course of refueling, transportation and storage of fuel elements;

- loss of heat removal from the nuclear core and other causes resulting in damage of fuel elements.

28. Nuclear safety of the PRR - the PRR property to reduce probability and consequences of any nuclear accident down to the established limits.

29. Nuclear-hazardous works at the PRR - any works at the PRR that can cause a nuclear accident.

1. GENERAL PROVISIONS

1.1. Nuclear safety rules for pulse research reactors (hereinafter - the Rules) establish the requirements for the technical solutions applied in the PRR design and aimed to ensure nuclear safety of the PRR as well as for the administrative and technical arrangement for nuclear safety assurance in the course of operation with due regard for the purpose, neutron and physical characteristics and structural peculiarities of the PRR.

1.2. Nuclear safety of the PRR is defined by technical excellence of the PRR design, quality of manufacturing, installation, adjustment and testing of the safety-related systems and components, their reliability in the course of operation, the equipment state diagnostics, quality and promptness of the equipment maintenance and repair, arrangement of the works, qualification and discipline of the workers (personnel).

1.3. Nuclear safety of the PRR is ensured by compliance with the safety regulations and rules and the PRR design requirements, safety culture, quality and completeness of the experimental research with regard to neutron and physical characteristics in the course of physical and power start-up of the PRR, the system of administrative and technical arrangements minimizing probability and consequences of any human errors and equipment failures in the course of the PRR operation in the start-up and power operation mode and in any other modes.

1.4. The Rules shall apply to all designed, constructed and operated PRRs, regardless of their type, with the exception of electro-nuclear neutron generators including a PRR and a neutron source in the form of a charged particle accelerator and a neutron-producing target.

1.5. The procedure for bringing of the operated PRRs into compliance with the requirements of these Rules shall be defined in accordance with the PRR operation license conditions.

2. Requirements for the pulse
research reactor design
aimed to ensure nuclear safety

2.1. General requirements

2.1.1. Safety-related PRR systems and components shall be designed with due regard for any potential mechanical, thermal, chemical and other impacts occurring under normal operation conditions and in case of any operational occurrences including design basis accidents taking into account external impacts of natural and human-induced origin.

2.1.2. The following shall be specified and substantiated in the PRR design:

- the lists of methodologies and calculation programs used for calculation estimation of the neutron and physical characteristics and substantiation of the PRR nuclear safety, application scope of the programs used and information on their validation in accordance with the established procedure;

- the design number of generated pulses and their rated power density;

- operation limits and conditions, safe operation limits and conditions and any other limits for all controlled neutron and physical, thermal, hydraulic and other characteristics affecting nuclear safety;

- the lists of systems and components subject to operability checks and verification of characteristics on the operating or shut-down reactor with indication of the state of the reactor and safety-related systems;

- appliances, devices, methods and frequency of the checks of safety-related systems for operability and compliance with the design characteristics;

- the procedure for the nuclear fuel loading into the reactor nuclear core and the procedure for the reactor bringing into the critical state;

- the list of nuclear-hazardous works in the course of the PRR operation and nuclear safety assurance measures in the course of their performance;

- conditions for safe handling of nuclear materials;

- conditions for activation of safety systems and levels of external impacts requiring the reactor shutdown in case of their exceedance;

- quantitative analysis of reliability, efficiency and fast response of the control and protection systems demonstrating that these parameters comply with the requirements of the regulatory documents prescribing such parameters;

- analysis of response of the control and other safety-related systems to any external and internal impacts, potential failures and malfunctions and failures of the main reactor equipment confirming absence of any responses hazardous for the reactor; in this case the most probable and hazardous failures, particularly the ones resulting in spontaneous transfer of the reactor into the critical state and a nuclear accident shall be specified;

- consequence assessment for design basis and beyond design basis accidents; in this case an accident with the nuclear core melting (destruction) shall be considered among beyond design basis accidents;

- information on the scope of information recording and storage in the device of "black box" type in order to enable identification of initiating events for the accidents, determination of the actual functioning algorithms for the safety-related systems and actions of the operating personnel.

2.1.3. Technical solutions used in the design shall provide:

- the possibility to bring the reactor into the safe state and into the complete sub-criticality state;

- negative power (temperature) reactivity coefficient of the APRR sufficient for the reactor bringing into the sub-critical state on fast neutrons after the power pulse initiation and subsequent switching to the sub-critical state on delayed neutrons through the use of the CPS control devices;

- the possibility to perform research in any nuclear core of the APRR with interconnected nuclear cores while ensuring the safe state of other interconnected APRR nuclear cores;

- the PRR safety in case of any design basis accident caused by any initiating event considered in the design with a coincident failure of any active component or passive component of safety systems with mechanical moving parts, or a human error affecting the nuclear accident development, or non-detectable failures not controlled during operation of the components affecting the nuclear accident development;

- state diagnostics for the reactor and safety-related systems;

- integrity and operability of the equipment used for recording and storage of information necessary for the accident investigation under the design basis and beyond design basis accident conditions.

2.1.4. The design shall define administrative and technical arrangements aimed to prevent any unauthorized access to the control and other safety-related systems.

2.1.5. Means for transmission of information to the external and internal emergency reactor control rooms under beyond design basis accident conditions shall be provided in the design.

2.2. Normal operation systems

2.2.1. Nuclear core and its components

2.2.1.1. Design of the reactor shall prevent any unintended changes of the nuclear core configuration, movement and (or) deformation and distortion of the nuclear core components and the reflector that cause reactivity increase and (or) deterioration of heat removal conditions resulting in damage of fuel elements in excess of the relevant limits or impairing normal functioning of the CPS control devices under normal operation conditions and in case of any operational occurrences including design basis accidents.

2.2.1.2. Design of fuel assemblies and fuel elements shall ensure non-exceedance of the relevant fuel element damage limits under normal operation conditions and in case of any operational occurrences including design basis accidents with due regard for:

- the design number and rated parameters of the reactor power pulses;

- physical and chemical interaction of the nuclear core materials and the coolant;

- shock and vibration impacts, thermal cycle loading, fatigue and material ageing;

- impact of any impurities in the coolant and fission products on corrosion of the fuel element claddings;

- impact of radiation and any other factors deteriorating mechanical characteristics of the nuclear core materials and integrity of the fuel element claddings.

2.2.1.3. Design of the nuclear core shall prevent autocatalysis of the chain nuclear fission reaction.

2.2.1.4. Design of the nuclear core and the CPS actuators shall prevent any blockage, ejection of the CPS control devices or their spontaneous disengagement from the CPS drives.

2.2.1.5. The design shall include analysis of the nuclear core thermotechnical reliability substantiating sufficiency of the margins provided in the design for non-exceedance of the safe operation limits for fuel elements.

2.2.1.6. Characteristics of the nuclear fuel, location of fuel elements, fuel assemblies, the CPS control devices and other nuclear core components shall eliminate any possibility for local criticality occurrence and chain nuclear fission reaction in case of the nuclear core destruction (melting).

2.2.1.7. Design of the nuclear core and the CPS control devices shall enable variation of the reactivity margin and power vensity value of the pulse restricting them to the maximum values specified in the operating organization's data sheet for the PRR.

2.2.1.8. The design of a fuel solution PRR shall provide for batch-wise remote filling of the nuclear core with nuclear fuel solution and monitoring of the fuel solution level in the nuclear core.

2.2.1.9. In case the combustion system for the fuel solution radiolysis products is used in the fuel solution PRR the reactor vessel strength shall be determined with due regard for the pressure increase in the vessel in the course of the radiolysis product combustion.

2.2.1.10. The following shall be defined in the design:

- reactivity margins as of the campaign beginning for all states of the nuclear core provided in the PRR design with assessment of error for the applied calculation methods and with due regard for any potential manufacturing tolerances of the nuclear core components;

- efficiency of the CPS control devices, fuel assemblies and experimental devices with due regard for their interference;

- sub-criticality of the reactor with the emergency protection control devices lifted;

- safe sub-criticality and complete sub-criticality of the reactor;

- reactivity effects and feedback coefficients providing for the APRR power pulse suppression;

- any potential sources and consequences of reactivity fluctuation;

- specific threshold fuel element breaking energy and the maximum permissible power density per a power pulse.

2.2.1.11. The following shall be also defined in the design of the PRR with the mobile nuclear core transported to the holding chamber (holding zone) for the period of temporary or long-term shutdown:

- conditions enabling to start the operations for transportation of the nuclear core to the holding chamber (the PRR sub-criticality, temperature regime of the nuclear core components, radiation situation, etc.);

- the list and technique for performance of any preparation operations aimed to bring the process systems, control systems, transportation and handling equipment into the state of availability for the nuclear core transportation;

- conditions of the nuclear core storage in the holding chamber and the scope of the nuclear core state monitoring in the holding chamber;

- state of the process systems, control systems and the equipment in the reactor room prior to commencement of any works for the nuclear core transportation from the holding chamber to the work site;

- the scope of control with regard to operability and parameters of the process systems and the reactor control systems after the nuclear core return from the holding chamber to the work site in the reactor room.

2.2.1.12. Reactivity margins shall be substantiated and basically sufficient for initiation of the required power pulse.

2.2.1.13. Correspondence between damages of fuel elements and activity of the primary circuit coolant with regard to reference radionuclides shall be defined in the design with due regard for efficiency of the coolant purification systems.

2.2.1.14. Analysis of dynamic processes in the nuclear core shall be performed for the PPRD, and the stability limit in the coordinates "average power - coolant flow rate" and in the coordinates "reactivity disturbance - reactivity disturbance rate" shall be determined. The safe reactor operation zone shall be defined subsequent to the stability analysis results.

2.2.1.15. Consequences of neutron leakage decrease from the nuclear core at the approach of the personnel, experimental devices and any other objects, as well as due to breakage of any reactor room civil structures and (or) filling of the reactor room and the nuclear core with water shall be considered in the design of the PRR with the nuclear core without a reflector.

2.2.1.16. Quality parameters with regard to chemical and radionuclide composition of the coolant shall be established in the design, and the engineering features and administrative arrangements for their maintenance and monitoring shall be provided.

2.2.1.17. The design shall provide for the engineering features and methods of leak-tightness control for fuel element claddings (fuel assemblies) on the shut-down and operating reactor in order to ensure reliable and timely detection of leaky fuel elements (fuel assemblies).

2.2.1.18. Fuel elements with different enrichment, burnable neutron absorbers, fuel elements with burnable neutron absorber and fuel elements with different nuclide composition shall have clear labeling (distinctive signs).

2.2.1.19. The possibility to unload the nuclear core and its components after a design basis accident shall be technically substantiated and provided in the design.

2.2.2. Normal operation control systems

2.2.2.1. NOCS shall ensure the reactor state monitoring and automatic and (or) remote control of the reactor systems in order to reach and maintain the neutron, physical and any other characteristics and parameters of the reactor within the prescribed range.

2.2.2.2. The lists of the controlled parameters (characteristics) and signals on the state of the reactor and the controlled parameters and control signals shall be specified and substantiated in the design.

2.2.2.3. The design shall provide for the CPS part within the NOCS ensuring reactivity (power) control under normal reactor operation conditions and in case of any operational occurrences.  The above-mentioned part of the CPS must include:

- automatic and (or) manual CPS controllers used to raise the reactor power to the required steady level and to ensure normal shutdown of the reactor;

- reactivity compensating devices used to compensate excessive reactivity margin in the reactor and to select the optimal position of other CPS control devices in the course of the reactor rising to power;

- additional engineering features used to increase sub-criticality of the reactor in case when total efficiency of the CPS control devices including the control devices of the reactivity controllers, reactivity compensating devices and emergency protection is insufficient to ensure sub-criticality corresponding to the safe state or the complete sub-criticality state of the reactor with due regard for potential reactivity release;

- the position monitoring and control system for the actuators of the CPS control devices;

- the system ensuring generation of power pulses through the use of the starter device or the reactivity modulator;

- at least two independent neutron flux density monitoring channels with indication devices ensuring the reactor power control. In this case at least one channel shall provide for the possibility to record any time variations of the average reactor power;

- at least two independent neutron flux density change rate (period) monitoring channels with indication devices;

- the control and position monitoring channel for the external (start-up) neutron source;

- monitoring and recording channels for the power pulse parameters (power pulse wave form and amplitude or power density per a power pulse);

- monitoring channels for the parameters of safety-related process systems.

2.2.2.4. In case the neutron flux density monitoring range is divided into several sub-ranges these sub-ranges shall overlap each other at least within one decade of the neutron flux density measurement units; automatic switching of sub-ranges shall be also provided.

2.2.2.5. In case the neutron flux density monitoring channels do not provide for the neutron flux density monitoring in the course of the nuclear core loading (refueling) the reactor shall be equipped with the additional monitoring system. This system may be removable and installed for the nuclear core loading and refueling periods; it shall include at least two independent neutron flux density monitoring channels with indication and recording devices.

2.2.2.6. The following shall be specified and substantiated in the design:

- quantity, functional distribution and efficiency of the CPS control devices as well as movement velocities of the CPS control devices within the reactor physical start-up period in the course of their calibration and the power pulse generation;

- methods and conditions for testing, replacement and take-down of the CPS control devices, their drives and other reactivity control devices for repair;

- hardware-based, methodological and metrological support of the reactivity effect and sub-criticality measurements with indication of the recommended algorithms and physical constants of the reactor kinetic equation, quantity and coordinates of the neutron flux detectors, the techniques for accounting of the spatial and temporal effects, the metrological validation methodologies for reactivity meters; in this case the operability check means and the warning malfunction alarm shall be provided for the reactivity meters.

2.2.2.7. The NOCS shall ensure:

- monitoring of the neutron flux density within the entire PRR power variation range, starting from the neutron flux density level  determined by the external (start-up) neutron source in the absence of nuclear fuel in the nuclear core;

- reactivity (sub-criticality) monitoring;

- the possibility to limit reactivity disturbance due to the starter device (the reactivity modulator) and the reactivity change rate to the value sufficient to obtain the rated power pulse parameters.

2.2.2.8. The APRR NOCS shall also ensure monitoring of other parameters and characteristics of the reactor defining the power pulse parameters prior to implementation of the starting reactivity power pulse.

2.2.2.9. The PPRR NOCS shall also ensure:

- stability of the reactivity modulation rate and depth;

- control of the power pulse frequency;

- vibration control for the reactivity modulator assemblies;

- position monitoring for the reactivity modulator control devices;

- amplitude control for each reactivity (power) pulse.

2.2.2.10. The NOCS of the fuel solution PRR shall ensure the power density value per a power pulse not resulting in any disturbances of the thermal stability conditions for the nuclear fuel solution.

2.2.2.11. The NOCS of each interconnected nuclear core of the multi-core APRR shall have an independent neutron flux density monitoring system recording mainly the neutrons only in this nuclear core.

2.2.2.12. In case the emergency protection control devices are not lifted the NOCS shall prevent any movement (position change) of other reactivity control devices.

2.2.2.13. The manual and automatic adjustment control devices and the compensating devices shall have intermediate position indicators and end position indicators.

2.2.2.14. The NOCS shall ensure automatic control of the final APRR availability for the power pulse in accordance with the availability control program correcting any human errors.

2.2.2.15. In case of any failure of the power pulse wave form recording and monitoring channel, or the pulse power density recording channel, or any other channel for monitoring of the reactor parameters defined in the design signals shall be received to stop the availability control program and to bring the reactor into the safe state. In this case the signal on the channel failure shall be generated.

2.2.2.16. The design shall provide for availability of the light and (or) acoustic alarms in the reactor control room in order to inform the personnel on the reactor state including:

- alarm upon reaching of the emergency protection activation setpoints by the reactor parameters (emergency alarm);

- alarm in case of the reactor parameter approaching to the emergency protection activation setpoints and any malfunction of the equipment (warning alarm);

- position indication for the CPS control devices and indication of voltage in the power supply circuits of the safety-related PRR systems (components) (indicating alarms).

2.2.3. Nuclear core cooling system (primary circuit)

2.2.3.1. The nuclear core cooling system (the primary circuit) shall ensure heat removal from the nuclear core under normal operation conditions of the reactor without any deviations from the established design limits with regard to temperature and temperature change rate for the core components, experimental devices and the coolant.

2.2.3.2. The following shall be specified and substantiated in the design:

- boundaries of the primary circuit;

- reliable operation of the primary circuit systems and components within the specified service life with due regard for any impacts possible under normal operation conditions and in case of any operational occurrences including design basis accidents;

- quantity and character of the impacts and operation conditions considered in determination of the primary circuit design service life.

2.2.3.3. It should be demonstrated in the design that strength of the reactor vessel and structures is ensured under normal operation conditions and in case of any operational occurrences including design basis accidents within the entire specified service life of the primary circuit.

2.2.3.4. The primary circuit pipelines shall be equipped with the devices for monitoring and prevention of any unacceptable displacements and vibrations.

2.2.3.5. In case any heat exchanging equipment is used to transfer heat from the primary circuit the design shall provide for the heat exchanging surface reserve sufficient to compensate for deterioration of its heat transfer characteristics in the course of operation.

2.2.3.6. Circulation pumps of the primary circuit shall have inertia sufficient to provide the required coolant flow rate in case of their power supply loss up to the moment when natural circulation of the coolant or the emergency cooldown system ensures residual heat removal without any exceedance of the operation limits with regard to damage of fuel elements.

2.2.3.7. The design shall provide for the following:

- monitoring of the nuclear core cooling system parameters with activation of the warning or emergency alarm upon reaching of the preset parameter limits;

- automatic protection against impermissible pressure increase or drop in the primary circuit under normal operation conditions and in case of any operation occurrences including design basis accidents;

- compensation of any coolant volume changes caused by the temperature regime variations for the nuclear core components;

- detection of the coolant losses in case of leakage and compensation of the coolant losses due to leakages (with indication of the maximum leakage flow rate compensated through the use of these means);

- protection of the primary circuit against unintended coolant drainage;

- means and techniques for detection of the primary circuit coolant leakage points and flow rates;

- purification of the coolant from impurities, fission and corrosion products.

2.2.3.8. Activation (disabling) of the primary circuit circulation pumps shall not disturb the sub-critical state of the PRR in case of any initiating event of design basis accidents.

2.3. Safety systems

2.3.1. Emergency protection

2.3.1.1. The design shall provide for the protective safety system within the CPS in order to ensure emergency protection (emergency shutdown) of the reactor.

2.3.1.2. Emergency protection of the reactor shall have at least two independent control devices or groups of control devices (the group shall consist of the control devices with a common drive independent from the others).

2.3.1.3. Efficiency and fast response of the emergency protection without the most efficient control device (group of control devices) shall be sufficient to bring the reactor into the sub-critical state in case of any operational occurrences including design basis accidents and to reduce power density in the nuclear core down to the level not causing any damage of fuel elements in excess of the limits established for design basis accidents.

2.3.1.4. The PPRD emergency protection response time including the lag coefficient of the recording hardware, response time of the actuators and the time for movement of the emergency protection control devices shall be less than the power pulse generation period.

2.3.1.5. Emergency protection shall be designed in such a way so that the commenced protective action would be completed to the full extent with due regard for the requirements of par. 2.3.1.3, and monitoring of the safety function performance would be arranged.

2.3.1.6. In case of an emergency signal from any emergency protection channel the emergency protection control devices shall be activated regardless of their position.

2.3.1.7. The emergency protection control devices shall have end position and (or) state indication.

2.3.1.8. Emergency protection shall perform its functions (shutdown according to the emergency protection signal and in case of any failures in the emergency protection system) regardless of the state of the CPS power supply sources.

2.3.1.9. In case of necessity the emergency protection control devices may be used for normal (scheduled) shutdown of the reactor.

2.3.2. Emergency nuclear core cooling system

2.3.2.1. The design of the PRR with forced cooling shall provide for the protective safety system in order to ensure emergency cooldown of the nuclear core in case of any failure of the normal (regular) cooling system.

2.3.2.2. The list of the reactor state parameters and characteristics used to activate the emergency nuclear core cooling system, the system actuation setpoints and conditions shall be substantiated in the design for all initiating events of design basis accidents.

2.3.2.3. Activation and disabling of the emergency nuclear core cooling system shall not disturb the sub-critical state of the reactor.

2.3.2.4. The design shall provide for the possibility to control the emergency nuclear core cooldown process both from the main and emergency control room of the reactor.

2.3.3. Control safety systems

2.3.3.1. The CSSs shall ensure state monitoring for the protective safety systems and their control during performance of the assigned functions.

2.3.3.2. The emergency protection hardware used in the CSS shall consist of at least two independent sets.

2.3.3.3. Each set of the emergency protection hardware shall be designed in such a way so that to ensure protection within the entire neutron flux density variation range via at least two independent channels:

- with regard to the neutron flux density;

- with regard to the neutron flux density change rate.

2.3.3.4. In case of necessity to divide the neutron flux density monitoring range into several sub-ranges the CSS shall provide for overlapping of these sub-ranges at least within one decade of the neutron flux density measurement units and for automatic switching of sub-ranges.

2.3.3.5. The CSS shall provide for the possibility to connect the recording device to each neutron flux density monitoring channel.

2.3.3.6. The list of the reactor state parameters and characteristics requiring the emergency protection actuation shall be specified and substantiated in the design. Emergency protection shall be activated at least in the following cases:

- upon exceedance of the emergency protection setpoint with regard to the neutron flux density level;

- upon reaching of the emergency protection setpoint with regard to the neutron flux density increase rate (or reactivity) in the course of the reactor operation at the steady power level or in the course of works with the reactor shut down;

- in case of any CPS power supply malfunction;

- in case of any malfunction or inoperability of any emergency protection channel for the neutron flux density level or increase rate;

- in case of any process signals requiring the PRR shutdown;

- upon deviation from the established operation characteristics of the PPRR reactivity modulator;

- upon actuation of any switches (buttons) intended for the emergency protection activation initiating.

2.3.3.7. The possibility to check generation and transmission time for the emergency protection signals without activation of the emergency protection control devices shall be provided for each channel and for the entire set of emergency protection hardware.

2.3.3.8. The emergency protection system shall provide for automatic monitoring and diagnostics of the emergency protection hardware sets and protection channels with display of information on any failures of the channels in the main reactor control room as well as generation of emergency protection signals in case of any failures of the emergency protection channels or hardware sets.

2.3.3.9. Permissibility and conditions for disabling of one emergency protection hardware set or one channel in the emergency protection hardware set shall be substantiated in the design.

2.3.3.10. Each emergency protection hardware set shall operate on the basis of the majority logic selected in accordance with the reliability analysis provided in the design.

2.3.3.11. The list of parameters and initiating events requiring automatic activation of the emergency nuclear core cooling system shall be presented and substantiated in the design.

2.3.3.12. The design shall provide for recording of the causes for activation of safety systems.

2.3.3.13. Failures of the information display and recording devices in the CSS channels shall not affect performance of the functions by these channels.

2.3.3.14. The possibility to activate the safety systems and to monitor the basic  parameters of the reactor from the emergency reactor control room in case of impossibility to carry out these activities from the main reactor control room shall be provided.

2.3.4. Emergency power supply sources

2.3.4.1. Emergency power supply sources shall provide power supply for the neutron flux density monitoring channels, position indicators of the CPS control devices as well as power supply of the systems (components) used for the nuclear core emergency cooldown.

2.4. Experimental devices

2.4.1. Assessment of the reactivity effects due to installation (withdrawal) of experimental devices shall be presented in the design.

2.4.2. The design shall ensure absence of local critical mass and deformation of the power density fields capable to cause any damage of the nuclear core components during installation of the experimental devices in the reactor.

2.4.3. In case of necessity the experimental devices shall be equipped with the detectors for monitoring of neutron flux density, thermal, physical and other safety-related parameters.

2.4.4. Design of the experimental devices shall prevent their spontaneous displacement or changes of their parameters in the course of installation (dismantling) and operation and also shall provide confinement of the tested elements in case of their breakage.

2.4.5. In case installation (withdrawal) of any experimental devices results in reactivity increase by 0.3 betaeff and more step-by-step reactivity increase with the interval not exceeding 0.3 betaeff shall be provided.

2.4.6. Design and engineering documentation for the experimental devices not provided in the PRR design shall be agreed with the PRR designers and the operating organization.

2.4.7. Experimental research of the impact of any new experimental devices on the neutron and physical characteristics of the reactor (reactivity margin, power density distribution, etc.) shall be carried out prior to their use in the PRR.

2.4.8. Conditions, scope and frequency of inspections of experimental devices for compliance with the design characteristics shall be defined in the design.

3. Nuclear safety assurance in the course of
commissioning and operation of the
pulse research reactors

3.1. Physical start-up

3.1.1. The PRR readiness for physical start-up shall be checked by the working commission and the nuclear safety commission appointed by the operating organization.

3.1.2. The working commission shall check:

- compliance of the works performed at the PRR site with the design;

- completeness of the reactor personnel;

- availability of the equipment used in the course of physical start-up, presence of the equipment testing reports and commissioning work completion certificates;

- availability of the operation, program and methodological, administrative and in-process documentation within the scope defined in the PRR documentation list for the period of the physical reactor start-up approved by the operating organization management;

- compliance of quality of the works performed in the course of the reactor construction and commissioning with the requirements of the general and individual quality assurance programs.

3.1.3. Results of the working commission activities shall be registered in the report approved by the director of the operating organization.

3.1.4. The nuclear safety commission shall check:

- readiness of the reactor for physical start-up taking into account the reports on elimination of any defects specified in the working commission report;

- implementation of the nuclear safety measures prescribed in the PRR physical start-up program and the nuclear safety assurance guidelines for the PRR physical start-up;

- preparedness of the personnel for commencement of the works in accordance with the physical start-up program, particularly availability of the permits for works in the area of atomic energy use for the PRR personnel.

3.1.5. Results of the nuclear safety commission activities shall be registered in the report approved by the director of the operating organization.

3.1.6. The provision approved by the director of the operating organization shall define the rights and liabilities if the officers and structural units of the operating organization, the PRR management and personnel with regard to nuclear safety assurance.

3.1.7. The physical start-up supervisor, shift supervisors and controlling physicists shall be appointed by the order of the operating organization, and their rights and liabilities shall be defined.

3.1.8. Delivery of nuclear materials to the reactor shall be permitted subsequent to fulfillment of the relevant conditions specified in the PRR operation license.

3.1.9. The procedure adopted in the operating organization for handling of nuclear materials (nuclear fuel) shall comply with Safety requirements for nuclear fuel storage and transportation at nuclear facilities.

3.1.10. The director of the operating organization shall issue the order on the PRR physical start-up subsequent to approval of the reports on elimination of any defects revealed by the working commission and the nuclear safety commission.

3.1.11. The PRR physical start-up shall be performed in accordance with the PRR physical start-up program agreed with the PRR designers and approved by the management of the operating organization.

3.1.12. All works on the PRR site at the physical start-up stage shall be performed in accordance with the sequence and scope defined in the PRR physical start-up program and with implementation of the administrative and technical arrangements prescribed in the nuclear safety assurance guidelines for the PRR physical start-up.

3.1.13. The PRR physical start-up program shall define the procedure for the nuclear fuel loading into the reactor and the procedure for the reactor bringing into the critical state; the list, description and sequence of the planned experiments shall be provided.

3.1.14. "Count-down curves" shall be plotted in the course of the critical mass gaining in accordance with the readings of at least two power monitoring measurement channels; in this case at least one "count-down curve" shall have "safe development".

3.1.15. The PRR physical start-up program for the APRR with interconnected nuclear cores shall include two sub-stages of the works, particularly:

- studies of the neutron and physical characteristics for each PRR nuclear core with other nuclear cores removed to the distance providing their minimal impact on the nuclear core under investigation;

- simultaneous studies of the neutron and physical characteristics of the interconnected PRR nuclear cores.

3.1.16. The nuclear safety assurance guidelines for the PRR physical start-up shall prescribe the nuclear safety assurance arrangements, contain the brief description of the CPS (including contingency starting equipment if any is used), as well as characteristics of the neutron flux density level and change rate monitoring channels, characteristics of the emergency protection channels, estimated values of critical loads and efficiency of the CPS control devices, assessment of the impact of the installed experimental devices and the coolant on the reactivity, permissible positive reactivity insertion rates during movement of the CPS control devices.

The nuclear safety assurance guidelines for the PRR physical start-up shall be approved by the management of the operating organization.

3.1.17. All orders of the physical start-up supervisor and operations performed by the personnel as well as any experiments and their results shall be registered in the order book, the shift daily log and the measurement log respectively.

3.1.18. The report shall be issued subsequent to the physical start-up results containing the physical start-up results and their brief analysis.

3.2. Power start-up

3.2.1. All structures, devices and systems provided in the PRR design shall be commissioned prior to commencement of the power start-up, and the documentation shall be prepared within the scope defined in the list of effective PRR documentation approved by the management of the operating organization.

3.2.2. Readiness of the reactor for power start-up and subsequent operation shall be checked by the working commission appointed by the order of the operating organization director and the State acceptance committee appointed upon the recommendation of the federal atomic energy use controlling agency in accordance with the procedure prescribed by the effective legislation.

3.2.3. The decision of power start-up shall be made by the State acceptance committee based on the report on elimination of any defects revealed by the working commission approved by the director of the operating organization.

The decision of power start-up shall be issued as the order of the operating organization.

3.2.4. The power start-up supervisor shall be appointed by the order of the operating organization, and his/her rights and liabilities shall be defined.

3.2.5. The PRR power start-up shall be carried out in accordance with the power start-up program adjusted in accordance with the physical start-up results, agreed with the designers and approved by the management of the operating organization.

3.2.6. The main stages of the works, the initial state of the reactor and the systems prior to commencement of each work stage, their hardware-based and methodological support as well as nuclear safety assurance measures shall be defined in the PRR power start-up program.

3.2.7. The power start-up results shall be registered in the report containing recommendations for the PRR operation as well as recommendations for adjustment of the operation documentation and the PRR safety analysis report.

3.3. Start-up and power operation mode

3.3.1. The PRR operation in the start-up and power operation mode shall be carried out based on the PRR experimental research program approved by the management of the operating organization subject to compliance with the requirements stated in the PRR operation process regulations and any other operation documentation as well as in accordance with the characteristics (parameters) specified in the PRR certificate.

3.3.2. The sample certificate for the pulse research reactor is given in Appendix 1.

3.3.3. The cyclogram of the reactor power operation, parameters of the planned power pulses, the initial (starting) state of the reactor and process systems as well as nuclear safety assurance measures with due regard for peculiarities of the future experimental research on the reactor shall be provided in the PRR experimental research program.

3.3.4. The PRR operation in the start-up and power operation mode shall be carried out only with the use of experimental devices specified in the PRR certificate.

3.3.5. The administrative and technical arrangements preventing any changes of the selected setpoints and parameters of the reactor and process systems prior to generation of power pulse shall be implemented before the reactor rising to power subsequent to reaching and checkout inspection of the required characteristics (parameters) of the reactor and process systems.

3.3.6. In case the requirements stated in the PRR operation process regulations or any other operation documentation are not fulfilled to the full extent in the course of the reactor preparation for operation in the start-up and power operation mode, or safe operation limits and conditions are violated in the course of the PRR operation in the start-up and power operation mode the reactor shall be switched to the temporary shutdown mode. Subsequent operation of the PRR in the start-up and power operation mode shall be possible only after elimination of the causes for the reactor switching to the temporary shutdown mode and in accordance with the written permission (instruction) of the operating organization director.

3.3.7. In case of any changes in the technical characteristics (parameters) specified in the PRR certificate the PRR operation in the start-up and power operation mode shall be permitted only subsequent to re-issuance of the PRR certificate.

3.4. Temporary shutdown mode

3.4.1. Prior to the PRR operation in the temporary shutdown mode the reactor shall be brought into the safe state; in this case the reactor sub-criticality value shall correspond to the value prescribed in the design, but not less than 2% (Кeff <= 0.98) with the emergency protection control devices lifted.

3.4.2. All works in the reactor room after the reactor bringing into the safe state shall be performed by at least two workers with registration of the reactor room attendance in the relevant log.

3.4.3. Maintenance, scheduled preventive maintenance, testing and operability checks of safety-related systems shall be carried out in accordance with the effective guidelines, programs and schedules approved by the chief engineer of the PRR.

3.4.4. Subsequent to completion of the works for maintenance, repair or replacement of any safety-related system components their operability and compliance with the design characteristics shall be checked with documentation of the results.

3.4.5. Nuclear-hazardous works on the PRR shall be performed in accordance with the technical resolution (work management plan) approved by the PRR supervisor (chief engineer) and defining the following:

- the purpose and list of the planned nuclear-hazardous works, sequence and technology of their performance;

- administrative and technical nuclear safety measures in the course of nuclear-hazardous works;

- calculations and experimental assessment of the impact of planned works on the reactor reactivity separately for each nuclear-hazardous operation.

3.4.6. The technology for performance of nuclear-hazardous works constantly repeated on the PRR when any reactivity changes due to the implemented operations is experimentally known may be described in the PRR operation manual and the PRR operation process regulations. In this case issuance of the technical resolution (see par. 3.4.5) is not mandatory.

3.4.7. The neutron flux density and its change rate shall be controlled in the course of any nuclear-hazardous works on the PRR; in this case the minimum setpoints shall be set for the warning and emergency light and acoustic alarm with regard to the neutron flux density level and change rate.

3.4.8. Nuclear-hazardous works shall be usually carried out with the emergency protection control devices lifted.

Any situations when nuclear-hazardous works are performed without lifting of the emergency protection control devices shall be defined in the operation manual and the PRR operation process regulations; in this case adherence to the requirements of par. 3.4.5 and 3.4.7 shall be mandatory.

3.5. Long-term shutdown mode

3.5.1. In case of the decision on the PRR switching to the long-term shutdown mode the operating organization shall develop the arrangements to ensure safety of the reactor in the long-term shutdown mode and to prevent premature operability loss for the safety-related systems (components), including corrosion of the fuel element claddings and casings of fuel assemblies in the reactor or in the repositories.

The scope and frequency of state monitoring for the PRR in the long-term shutdown mode shall be defined in the PRR operation manual.

3.5.2. Complete sub-criticality of the reactor shall be ensured prior to commencement of the works for the reactor switching into the long-term shutdown mode; in this case the sub-criticality value shall correspond to the value prescribed in the design, but not less than 5% (Кeff <= 0.95).

3.5.3. Feasibility of the nuclear fuel unloading from the nuclear core shall be considered with due regard for expected duration of the long-term shutdown mode and other factors.

3.5.4. The preservation methods applied for the reactor systems and the scope of the reactor maintenance shall not result in reduction of the specified service life for any safety-related systems (components) and shall comply with the design requirements.

3.5.5. The scope and frequency of the state monitoring for the reactor in the long-term shutdown mode shall be defined in the reactor operation manual.

3.5.6. In case of necessity to switch the reactor from the long-term shutdown mode into the start-up and power operation mode the works shall be carried out in accordance with the program approved by the PRR supervisor (chief engineer).

3.6. Final shutdown mode

3.6.1. The final PRR shutdown mode shall be introduced by the resolution of the federal atomic energy use controlling agency.

3.6.2. In case of the reactor operation in the final shutdown mode the operating organization shall implement administrative and technical arrangements in order to prepare for the future works on the reactor decommissioning, including the nuclear fuel unloading from the nuclear core in accordance with the technique defined in the design and removal of nuclear materials from the reactor site.

3.6.3. The report on the results of the works for removal of nuclear materials from the reactor site shall be submitted to the federal atomic energy use controlling agency and to Gosatomnadzor of Russia.

4. Control over compliance with the Rules

4.1. The operating organization shall ensure continuous control over compliance with these Rules and shall arrange annual inspection of the nuclear safety conditions at the PRR by the commission appointed by the order of the operating organization director. The inspection results shall be registered in the annual PRR nuclear and radiation safety assessment reports submitted to the federal atomic energy use controlling agency and to Gosatomnadzor of Russia.

Appendix

(sample)

Certificate

of the pulse research reactor

1. PRR name and type ________________________________________

2. PRR purpose ________________________________________________

3. Location ______________________________________________

4. Operating organization ___________________________________

5. PRR designers ______________________________________

6. PRR commissioning date  _________________________________

7. Specified service life (years)  ____________________________

8. Basic parameters of the reactor:

 number of nuclear cores, pcs. ________________________________

 nuclear core dimensions (diameter x height), mm  ________________

 fissile isotopes and their quantity, kg _______________________

 nuclear fuel:

 nuclide composition ____________________________________________

 enrichment, % _______________________________________________

 moderator _________________________________________________

 reflector __________________________________________________

 coolant _______________________________________________

9. Basic neutron, physical and other characteristics of the reactor:

 reactivity margin, betaeff _________________________________

 sub-criticality of the reactor after lifting of the emergency protection

 control devices, betaeff ___________________________________

 safe sub-criticality, betaeff __________________________

 complete sub-criticality, betaeff __________________________

 prompt neutron lifetime, s _______________________________________

 effective fraction of delayed neutrons, % _________________

 impulse fraction of delayed neutrons, % _________________

 total value and basic components of the power

 (temperature) reactivity effect _______________________

 maximum neutron flux density, n/sq.cm x s _______

10. Power pulse limits:

 maximum power density per the rated power pulse,

 J __________________________________________________________

 maximum super-criticality for the power pulse

 initiation with prompt neutrons, betaeff ___________________

 permissible reactivity increase rate per a power

 pulse, betaeff/s _________________________________________

 maximum power pulse amplitude, kW __________________________

11. Total negative reactivity inserted for suppression

 of the power pulse and its components, including:

 negative power (temperature) reactivity effect,

 betaeff _____________________________________________________

 negative reactivity introduced by the CPS control devices,

 betaeff _____________________________________________________

12. Protective safety systems ___________________________________________

13. Characteristics of the CPS control devices ____________________________________

14. Additional reactivity control devices and their efficiency, betaeff ________________________________________

15. Emergency protection channels for the neutron flux density level (number of channels and type of instruments) _____________________________

16. Emergency protection channels for the neutron flux density increase rate (number of channels and type of instruments) _____________________________

17. Neutron flux density level and increase rate monitoring channels (number of channels and type of instruments) _____________________________

18. Neutron flux density level monitoring channels with recording devices (number of channels and type of instruments) _____________________________

19. Experimental devices and reactivity introduced by them, betaeff _______________________

20. Certificate is issued on the basis of _______________________________________

21. Certificate is valid till  "__" _________________.

"__" ________________  Director of the operating organization

 L.S.

 Full name, signature