The Characteristics and Irradiation Capabilities of MARIA Research Reactor in NCBJ Świerk

The high flux research reactor MARIA is a water and beryllium moderated reactor of a pool type with graphite reflector and pressurised channels containing concentric six-tube assemblies of fuel elements. It has been designed to provide high degree of flexibility. The fuel channels are situated in a matrix containing beryllium blocks and enclosed by lateral reflector made of graphite blocks in aluminium cans. The MARIA reactor is equipped with vertical channels for irradiation of target materials, a rabbit system for short irradiations and six horizontal neutron beam channels. The MARIA reactor reached its first criticality in December 1974. The reactor was in operation until 1985 when it was shut down for modernization. The modernization encompassed refurbishment and upgrading of technological systems such as: enlargement of beryllium matrix, inspection of the graphite bocks, upgrading of ventilation and temperature systems.


MARIA research reactor description
The high flux research reactor MARIA is a water and beryllium moderated reactor of a pool type with graphite reflector and pressurised channels containing concentric six-tube assemblies of fuel elements.It has been designed to provide high degree of flexibility.The fuel channels are situated in a matrix containing beryllium blocks and enclosed by lateral reflector made of graphite blocks in aluminium cans.The MARIA reactor is equipped with vertical channels for irradiation of target materials, a rabbit system for short irradiations and six horizontal neutron beam channels.The MARIA reactor reached its first criticality in December 1974.The reactor was in operation until 1985 when it was shut down for modernization.The modernization encompassed refurbishment and upgrading of technological systems such as: enlargement of beryllium matrix, -inspection of the graphite bocks, -upgrading of ventilation and temperature systems.
The second step of upgrading the technological system was done from 1996-2002 (during regular maintenance) and it was consisted with: replacement of heat exchangers, replacement of instrumenttation and control system, upgrading of radiation protection system, modernization of fuel element integrity monitoring system.The main areas of reactor application are as follows: production of radioisotopes, testing of fuel and structural materials for nuclear power engineering, neutron radiography, neutron activation analysis, neutron transmutation doping, research in neutron and condensed matter physics.For today the NCBJ has a program for MARIA research reactor operation till 2030.

Characteristics of MARIA reactor for installation loops and rigs
MARIA reactor core contains the fuel assemblies which are installed in pressurized channels embedded in matrix sockets.The matrix is composed of beryllium blocks which are fastened to the support slab in reactor pool on the level +2.75 m [3].Beryllium blocks of the core matrix as well as the graphite blocks creating the radial reflector are positioned in the sockets of separator slab on the level -1.4 m (6x8) Fig. 1 and Fig. 2. The possibility of placing of the experimental channel, i.e. channels, rigs and loops depends on the two factors: of the position in the core and arrangement and dimensions of holes in the support slab.
The place within in the core can be matched to any experimental device by means of constructing suitable beryllium and graphite blocks.

Neutron irradiation services
Neutron irradiation services provided at the MARIA research reactor mainly include radioisotope production.Irradiation services are performed in various facilities in the MARIA reactor, with proper account for the required neutron flux 1, irradiation time, and target mass and geometry.The standard vertical in-core isotope channels as well as special ones equipped with hydraulic transport system are in operation.From 2010 in MARIA reactor started irradiation of uranium plates for Mo-99 production.Irradiations are carried out in two molybdenum channels and irradiated plates are sent to Petten facility in the Netherlands for processing.From September 2014 MARIA offers special irradiation in converter of 14 MeV neutrons.

References
[1] G. Krzysztoszek, Full core conversion from HEU to LEU fuel in MARIA reactor, 9 th IAEA TM, Samarkand, Uzbekistan 3-5 June 2015.-Main characteristics and data of MARIA reactor are as follows: • maximum power 30 MW (th) • thermal neutron flux density 3.0 ×10 -The main areas of reactor application are as follows: • production of radioisotopes, • research in neutron and condensed matter physics, • neutron radiography, • neutron activation analysis, • neutron transmutation doping, • testing of fuel and structural materials for nuclear power engineering.• MARIA reactor core contains the fuel assemblies which are installed in pressurized channels embedded in matrix sockets.• The matrix is composed of beryllium blocks which are fastened to the support slab in reactor pool on the level +2.75m.• Beryllium blocks of the core matrix as well as the graphite blocks creating the radial reflector are positioned in the sockets of separator slab on the level -1.4m (6x8) Fig. 1, 5. • At the support slab for the fuel and loop channels (Fig. 6) there have been made altogether 33 connectors to be used for the fuel channels.

Characteristics of MARIA reactor for installation loops and rigs
• The possibility of placing of the experimental channel, depends on the two factors: -the position in the core, -arrangement and dimensions of holes in the support slab.
• Distribution of openings, i.e. the sockets in the mounting plate is totally determined by its construction.
• On the mounting plate the were located the following sockets: -1 pc. of diameter 112 mm for the tube of Field type , -4 pcs. of diameter 112 mm for the channels of U type, -1 pc. of diameter 160 mm for the channels of U type, -1 pc. of diameter 900 mm for the channels of U type, -2 pcs. of diameter 112 mm to be compatible with sockets of diameter 150 mm, -1 pc. of diameter 220 mm, -1 pc. of diameter 170 mm.
• Distributions of gamma generation in steel are shown in Fig. 7 and 8. Fig. 7. Correlation between the heat generation in steel and the average power to be generated in the adjoined channels.• Between the experimental hall and reactor hall there are two hatchways in the region of loop installations of overall dimensions: 388 x 968 cm and 388 x 628 cm.
• These hatchways are to be used at construction of the loop installations and their shielding by using the main overhead crane of lifting capacity 16t.
• For the expansion of the loop installations it have been provided the culverts in the building wall enabling to pulling out the ancillary devices to the pavilion adjoining to the reactor building.
• The pipelines and instrument leads of experimental installation, by means of following routes: -Installation channels running in side the shielding walls of the storage pool and sloping down on the level -1.7m; -Culverts in the shielding hall of the reactor pool on the level +5m (for the instrument leads).
• The heavy and requiring effective shielding the equipment and installation of the loop circuits are set up in the experimental hall.
• Admissible load of floors in that place is 6 t/m 2 .
Fig. 1: a) vertical cross-section of the reactor pool, b) top view of the reactor core and reflector.

-
The research reactor MARIA is operated at the National Centre for Nuclear Research; -It is a water and beryllium moderated reactor of a pool type with graphite reflector and pressurised channels; -The fuel channels are situated in a matrix containing beryllium blocks;

Fig 3 .
Fig 3. A typical configuration of the MARIA reactor core with molybdenum channels.

Fig. 8 .
Fig. 8. Relative distribution of gamma heat generation in steel alongthe vertical axis of the channel for irradiation.