Domanus, J.C.

The DR1 reactor at Risø is used as a neutron source for neutron radipography. In the doublebeamneutron radiography facility a neutron flux of an intensity of 1,4 and 1,8 x 106 n. cm-2 • s-1 reaches the object to be radiographed. The transport and exposure container used for neutron radiography of irradiated nuclear fuel rods is described, and the exposure technique and procedure are reviewed. The mode by which single neutron radiographs are assembled and assessed is described. This report will be published in the "Neutron Radiography Newsletter" (a publication of the American Society for Nondestructive Testing)

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Downloaded from orbit.dtu.dk on: Dec 19, 2017Double beam neutron radiography facility of the Research Establishment RisøDomanus, Joseph CzeslawPublication date:1977Document VersionPublisher's PDF, also known as Version of recordLink back to DTU OrbitCitation (APA):Domanus, J. C. (1977). Double beam neutron radiography facility of the Research Establishment Risø.  (Risø-M;No. 1955).A. E. K. Risø Risø-M-G!fD Title and authors) DOOBLK warn wmmm lAoioaum FACILITY of the atSlMCT BATHatTS—ItT US« by J . C. D M * »77 Metallurgy Ciana'si ftwaacfft) Abstract Tha SRI raactor at Ilia* ia w e d aa a neutron source for neutron radiography. In tha doublabeea neutron radio-graphy facility a neutron flux of an intanaity of 1.4 6 -2 -1 and 1.8 x 10 n. ca • • raaehaa tha object to be radiographed. Tha transport and exposure container used for neutron radiography of irradiated nuclear fuel rods is described, and tha exposure technique and procedure ara reviewed. The node by which single neutron radiographs ara asseabled and asaassad is described. This report will be published in the "neutron Radiography Newsletter" (a publication of the American Society for Nondestructive Tasting). Copies to Available en request from the Library of the Danish Atomic Energy COHUBISSJOU (AtossesxVfUwsasaisvioB . Bibliotek), JUs#,»tt-4«00Roekilde, Denmark *l Telephone! (Of) t l it 01. est. tU. f |a»i 411H I DOUBLE DEMI MEVTKOM RADIOGRAPHY FACILITY of tha RESEARCH ESTABLISH«« RISØ J.C.Domanus Nuclear Department Elsinora Shipbuilding A Engineering Co.»Ltd. Dk-3000 Helsingør.Denmark 1. UH'ROUUITIOM To ba able to perform neutron radiography of irradiated fual rods tha DR1 raactor was adapted for that purpose. Hany of tha fual rods to ba axaainad by aautren radiography ara fabricated at Ris« and axe irradiated in the 10 MH DR3 raactor. After irradiation tha rods ara first transported from tha DR3 to tha Ris« Hot Cells, where the fuel elements are disasseabled and are undergoing different nondestructive and destructive post irradiation exaaina-tions. One of these MDT method* is neutron radiography. In the Hot Cells the rods are placed in special transport containers in which they are transported to tha neutron radiography facility at the DR1. Also fual elements arriving to Ris« for post irradiation examination are first disassembled in the Hot Cells. There tha individual rods ara loaded to the transport container and sent to the DR1. Short fuel pins of a 170 as length till full-size power reactor rods up to 3 a long have baen neutronradiogrsphed at Ris«. Routine neutron radiography has started lata in 1975 and since then about 1500 neutron radiographs ware taken. * working under contract with Research Establishment Rls«,DK-4000 Roskilde, Denmark - 2 -2 . THE QUI REACTOR AS HEOTBOM SOURCE As neutron source for neutron radiography the DRl reactor is available at Rise. The technical data of the reactor are the following: Thermal output - 2 kH Designer - Atomics International, USA Date critical - Aug. IS. 1967 Coolant and moderator temperature - light water, 25 C Reflector - graphite Fuel - Uranyl sulphate Enrichment - 19,9% U . „ content - 1 kg Max. neutron flux: thermal - 6 x 10 , fast - 12 x lO* n/cm .s This reactor, which is used for training and basic research purposes has been adapted to perform neutron radiography. 3. THE DOUBLE BEAM NEUTRON RADIOGRAPHY FACILITY The Risø double beam neutron radiography facility is schematically shown on fig. 1. Two graphite blocks (3) have been removed from the reflector (1), thus permitting the neutrons from the reactor core (2) to emerge through the reactor shielding as two beams (4) of a 10 xlO cm cross section. The neutron flux reaching the object to be radiographed has an inten-6 2 6 2 sity of 1.8 x 10 n/cm .» at the left port and 1.4 x 10 n/cm .s at the right port. The irradiated nuclear fuel rods are transported from the Rot Cells to the DRl reactor in a dual-purpose transport/exposure container (5). To the back of this container a steel rod (6) is attached by the use of which the rod (8) can be pushed out of the container and positioned before the two neutron ports This part of the rod which has left the shielding container (5) enters a shielded (7) ^ enclosure made of concrete. The imaging foil is introduced behind the fuel rod to be radiographed by means of the mechanism (9) consisting of two curved guides, which accomodate the foil. The neutron beam, originating at the reactor core (2), is collimated ir. the graphite collimator, having an inlet of 2 ca (vertically) x S cm(horicortally), and an outlet of 10 x 10 cm. The distance between the inlet and the exposure surface is 220 ca, which gives an L/d ratio of 110 (in the vertical direction). - 3 -The cadmium ratio (measured with gold) is 4.2 at the left port (1.8 x 10* n/cm2/s) and 3.8 at the right port (1.4 x 10 n/cm .S). 4. TRANSPORT AMD EXPOSURE CONTAINER For the purpose of transport of fuel elements between the Hot Cells and the DRl reactor two multipurpose transport/exposure containers are used. One is designed to accomodate fuel rods up to 2.5 m in length and the other up to 4.5 m. In the Hot cells fuel rods to be neutron radiographed are placed in an aluminium canning tube (wall thickness of 1 mm) which protects the container from contamination and at the same time serves for manipulation of the rods during neutron radiography. This Al canning tube, open on one side,is closed by a plug after the rod has been placed inside of it. A steel rod is fastened to the other end of the canning tube. This steel rod can be extended to such a length as to be able to push the rod in the canning tube to the desired posi-tion into the neutron beam during radiography. At the end of the steel rod a square or a hexagonal plate (see 6 in fig. 1) can be affixed. With this plate rotation of the rod is possible by 90 (square plate) or 60 (hexagonal plate) increments. This rotation is used, when a new projection of the rod during neutron radiography is desired. At the bottom end of the transport/exposure container a horizontal plate is connected (seen on fig. 1 under the plate 6). In this plate holes have been drilled at 10 cm distances and in those holes a stop is inserted against which the rotation plate (6) is pressed. Going from one position during neutron ra-diography to the next one, one removes the stop, puts it in the next consecu-tive hole and shovs the rod in the canning tube by 10 cm. At the end of a series of neutron radiographs the steering steel rod is pulled back (to the left on fig. 1) and the rod returns to the shielded posi-tion in the exposure container. I* another projection for neutron radiography is necessary the rod can be then rotated. If, however, the neutron radiography is terminated the upper end of the exposure container (to the right on fig. 1) is closed by an appropriate shielding plug. 5. EXPOSURE TECHNIQUE Neutron radiography of irradiated fuel rods is performed at Ris* using - 4 th* transfer technique. A 0.1 an Dysprosium imaging foil is used (40 a 120 am). This foil is introduced through the guiding mechanism (9 on fig. 1) to be in close contact with the rod under examination, after the exposure (about 30 sua for Agfa-Cevaert Strueturix 04 film or 90*ia for Kodak single coated SB fil«} the Dy foil is renoved fron the exposure nechanisn (9) and transported to the darkrooa. Sere X-ray fila is placed at both sides of the foil and the foil with the filn is inserted into a plastic vacuum casette (which assures good contact between the foil and fila). The filns are exposed by the Dy foil over-nignt and are developed next day in standard X-ray processing solutions. The fila which was exposed in contact with that side of the foil which was facing the fuel rod is used for essetenant purposes and the other fila (showing a less sharp picture) is used for filing purposes only. For routine neutron radiography the double coated M X-ray film is vsed aa with this fila reasonable exposures can be used during a larger number of neutron radiographs. The single coated SB fila is used in special instances, where neutron radiographs of higher quality are required and the longer expo-sure tine is acceptable. 6. EXPOSURE pwoexmrut The fuel rod under exanination is exposed through both neutron ports (4 on figl 1). The first exposure starts when the top of the rod is positioned approxiaately in the aiddle of the right part. Simultaneously with the exposure through the right port an exposure through the left port occurs. Due to the differences in the neutron flux intensities the exposure through the left port is a little shorter than through the right port (25 and 30nin respectively for the D4 fila). After the termination of the first exposure (through both ports) the rod is moved by 100 an into the next exposure position. After four consecutive ex-posures (with a 100 ma, shift between then) the rod is moved by 500 ma and a series of four exposures with a 100 ma shift occurs. Ti* distance between the neutron port axis being 385 ma there is an overlap of the consecutive exposures. The developed filas are next assembled in such a way aa to give a single neutron radiograph of the whole rod. This occurs by cutting the overlapping parts of the filn. At the bottoa of each neutron port two cobalt wires are located. The distance between these two wires in the left port is 80 ma and in the right port 35 ma, whereas the distance between the wires in both ports (left as wall - S -as right) Is 100 am. Tlw vires are reproduced oa the neutron radiographs as whits lines. Wg measuring the distance of the vires on one radiograph one can see whoather the picture was taken through the left or the right port. Cutting of the overlapping parts of the neighbouring radiographs occurs after measuring the 100 a* distance between the corresponding wires. 7- **'""T or jaantm Mwoc»Ar»s The developed centrem radiographs are assembled to give a picture of the whole fuel rod under examination. They are neat assessed to find defects and measure dimensions. The search for defects is concentrated on five areas cf the rod: fuel, cladding, plenum, plugs and instrumentation, which may be included in the fuel rod. In the fuel,pellets are osaminert for cracks, chips, dishing and central void. Fuel-to-clad and pellet-to-pellet gap are revealed and assessed. The pre-sence of hydrides in the cladding or plug* can be also revealed. all irregularities in the plenum (soring, spring sleeve or disc dis-placement) are well visible on the radiographs. The fuel column length as well as tep of fuel colaen to plug distance is measured. An attempt was made to introduce a classification of defects revealed by neutron radiography, in which 20 types defects in the above mentioned five areas are assessed according to their location and intensity. Fig. 1. Double bean neutron radiography facility at Risø. Graphite reflector Reactor core Two graphite blocks removed Two neutron beams (10 x 10 cm) Lead container to transport and handling of irradiated fuel rods Rod to positioning of fuel rod during radiography Concrete blocks for radiation shielding Tube supporting the fuel rod Mechanism for Introduction of imaging foils behind fuel rod to be radiographed. 

Double beam neutron radiography facility of the Research Establishment Risø

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Double beam neutron radiography facility of the Research Establishment Risø

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