As a part of international technical assistance to Ukraine and, in particular, to the Chornobyl NPP (ChNPP) and Object «Shelter» foreign devices and systems of radiation monitoring were supplied. Foreign devices are basement of Radiation Monitoring System (RMS) of New Safe Confinement (NSC).
Regardless of its technical specifications, those devices have got one significant disadvantage – high price. Under conditions of uncertainty with international financing of disassembling works of Object “Shelter” and exploitation of NSC, this fact will be a burden on the budget of Ukraine.
In this case, development of radiation monitoring devices which are compatible with current radiation monitoring automated systems of ChNPP becomes a relevant objective. Those new devices should have the same technical specifications but should have lower cost of possession.
In this document, we are introducing compatible device which has similar technical specifications to Mirion GIM-204 gamma-radiation measurement facility, which is a basement of current gamma exposure rate (GER) control of NSC.
Compatible device requirements
Due to the fact, that exploitation period of RMS of NSC is exciding exploitation periods of separate components (including GER sensors), compatible device should guarantee full functional and exploitation compatibility to devices like Mirion GIM204. The main requirements are:
- measurement scale;
- compatible hardware and software interface with RMS of NSC;
- local emergency and warning system (alarm);
- resistance to external influences.
- dimensions of processing (compute and communication) block with compatible fastening points;
- possibility of division of computing and measurement units as well as their separate installation;
- local indication (dose, faults, etc.);
- remote emergency and warning alarm on the place where the sensor is installed;
- availability of backup power supply (internal battery);
- compatible local management system;
- compatible hardware and software interface (1 RS232, 2 RS484, 1 Ethernet);
- fully-compatible analog and digital inputs/outputs;
- functional compatibility with Mirion Mass2 software.
Proposed solution and description
The architecture of the analog device is based on the module-block principle that is providing flexibility and scalability of this solution. Also, it is providing compatibility with current and prospective detectors and automated RMS.
The structure of analog device consists of the following components:
- detection unit;
- management unit;
- power supply unit;
1. Detection unit
Following unification principles with existing management systems of ChNPP and also, based on positive experience of operation of Integrated Control System (ICS), as a part of RMS of Object “Shelter”, we decided to use BDBG-09 as a part of detection unit. This device provides measuring scale of ambient dose equivalent rate (ADER) of gamma- radiation from 0.05 uSv/h to 10 Sv/h with a relative basic error ±17%.
These figures are equivalent to Mirion GIM-204. Beside this, BDBG-09 are produced in waterproof bodies, which significantly expands the range of application of further devices.
Never the less, compatible device, that was developed, does not limit in usage only BDBG-09 detector. As for now, there are several promising detectors that are on R&Dstage.These detectors are based on developed by our partner - InterAtomInstrument, based on scintillation monocrystals that are produced in Ukraine. These detectors allow to calculate not only GER but also energy spectrum of gamma radiation.
2. Management unit
2.1 Data acquisition unit
Data acquisition unit is based on industrial microcontroller and provides interface to detector and data processing unit.
2.2 Data processing unit
Data processing unit is based on industrial microcontroller. This unit is in charge of acquisition and storage of data that is coming from detector; mathematical data procession (digital filtering, etc.); servicing and processing of data. This unit is also providing a data interface to the data to external users and also provision of this data to a display unit (local analytical panel).
2.3 Switching unit
Is based on microcontroller and has got standardized interface with the data processing unit and provides communication interface with RMS. In this case compatibility of analog device with different RMS is provided by changing only one unit
2.4 Display unit (local analytical panel)
Local analytical panel is an industrial display, which shows current GER and also historical, analytical and calculated measurement data into graphical representation. The analytical panel is optional, and it is not influencing on general system performance.
2.5 Local alarm unit
This block is based on microcontroller that is controlling visual and sound alarm, that is mounted on management unit and also external alarm at the place of installation of sensor if necessary.
2.6 Relay and analog signal unit
Provides analog and digital signals compatibility with Mirion GIM-204. Optional and does not causes any influence on system.
3. Power supply unit
Provides power to the detection and control units. Implemented using modular principles and, depending on chosen item could provide power input from AC 220V, AC 42V, DC 24V. Optionally, it can be equipped with a battery, to ensure autonomous power supply.