For more than 50 years AO "NZHK" has supplied high-quality nuclear fuel for nuclear reactors in Russia, Ukraine, in the countries of Europe and Asia (Bulgaria, Hungary, Yugoslavia, Poland, Holland, Germany, Czechia, Korea, Iraq, Libya, Kazakhstan and Uzbekistan).
Nuclear fuel quality assurance is considered to be a main field of AO NZHK subdivisions activity aimed at satisfaction of Customer requirements and primarily at ensuring the safe use by the Customers of nuclear fuel produced at AO NZHK.
Nondestructive test systems are primarily used in the process of nuclear fuel production at AO NZHK with the purpose to prevent non-conformances to the specified requirements.
Non-destructive tests are performed using all well-known non-destructive test methods, i.e. acoustic, radiation, magnetic, eddy-current, penetrant fluid test (capillary method and leak test),visual measurements, thermal and technical diagnostics.
Main procedures on nondestructive test performance are developed both independently and in cooperation with the leading applied institutes, scientific institutes of the Russian Federation Academy of Science and Academy of Science of the Siberian Branch (VNIINM, VNIITFA, KTINP et al.).
The most nondestructive test systems were developed by a specially created Research Laboratory consisting of 21 nondestructive test (NDT) specialists of level II and four NDT specialists of the (highest) level III.
Acoustic methods are used during the following tests:
- tests of sealing girth weld joints of VVER-1000 and VVER-440 fuel elements (FEs) made by electron beam welding (EBW) and butt-resistance welding (fig.1);
- cladding separation test (fig.2);
- technical diagnostics of the equipment used for nuclear fuel production;
- ultrasonic method of the aggressive liquids levels and their concentration measurements (fig.3).
Fig 1: ULTRASONIC TESTS OF GIRTH WELD JOINTS OF VVER-440 AND VVER-1000 FES.|
Fig 2: ULTRASONIC TESTS OF NON-ADHESION|
Fig 3: ULTRASONIC TESTS OF AGGRESSIVE LIQUIDS LEVEL AND CONCENTRATION|
NDT radiation methods are used in the following cases:
- radiography of sealing girth weld joints of VVER-1000 and VVER-440 fuel elements;
- radiography of weld joint samples during fabrication of the equipment used in the nuclear fuel production;
- radiography of fuel meat of research reactors FEs;
- neutron tests to determine fuel enrichment in VVER-1000 FEs;
- gamma sorption method for testing of fuel column of the VVER-440 and VVER-1000 (Co57) FEs (fig.5);
- gamma sorption method for testing of fuel pellets compactness of the VVER-440 and VVER-1000 (Cs-137) FEs (fig.4);
- gamma sorption method for testing of fuel meat density of research reactor FEs(fig.6);
- albedo method for measuring the cladding thickness of research reactor FEs;
- gamma-sorption test method.
Fig 4: DETERMINATION OF FUEL PELLETS COMPACTNESS|
Fig 5: FUEL COLUMN X-RAY TESTS OF VVER-440 AND VVER-1000 FEs.|
Fig 6: RADIATION TESTS OF CLADDING WALL AND FUEL COLUMN THICKNESS.|
Eddy-current test method is used in the following cases:
- eddy-current control aimed at detection of the available fuel column locators and determination of their quantity in VVER-440 and VVER-1000 FEs;
- eddy-current control of surface defects;
- eddy-current control of coatings (anodized films on FE surface).
Penetrant fluid tests:
- Leak detection is used for tests of the VVER-440 and VVER-1000 FEs leak-tightness;
- Capillary method is used in the process of fabrication of the equipment for nuclear fuel production.
Visual measuring (optical) tests of geometrical dimensions:
FE diameters, length and bending.
Thermal test method for control of internal pressure of VVER-440and VVER-1000 FEs.
Lately the intensive re-equipping of NDT instrumentation stock takes place using the best models of well-known and recognized firms, such as Philips, Panametrics, Sonics, NNC, Kraut Kramer, Siemens, Seifert, Artvik, Mettler and industrial workstations of such firms as Texas, Microsystems, Proline, Advantech. Object interfaces are based on the components of National Instruments. Application software for these components is developed using programming products of LabVIEW.
Microsoft c/ctt, Borland c/ctt, LabWindow/CVI, Microsoft FOX PRO, Microsoft Visual Basic, Microsoft Access, Informix Online Server, SCCO UNIX software is used in automated systems and installations of the produced items control.
Recent developments of our specialists:
- X-ray device for fuel meat introscopy;
- - X-ray tomograph for tests of EBW joints of VVER-440 and VVER-1000 FEs;
- Automated line for cylindrical items testing in order to control their geometrical dimensions using ultrasonic methods;
- Automated ultrasonic installation for tests of EBW and BRW (butt-resistance welding) joints of VVER-440 and VVER-1000 FEs ( on the basis of SONIX boards).
All installations have know-how units and patented ones. The following objects are patented: unique X-ray, g
- and b
-radiation detectors, procedures of tests performance and special samples of metrological support.
AO NZHK personnel is always working with views for the future. Permanently the studies in the field of non-destructive tests are performed. At present the procedures on use of acoustical -emission apparatus and digital X-ray technique are developed.
Fig 7: DIGITAL X-RAY INTROSCOPY DEVICE.|