E P R I Jou rna l , Vol. 13, No. 3, pp. 38-40 ( A p r . / M a y 1988) The Electrical Power Research Institute (EPRI) has developed a novel

technique for on-line detection of wear in key power plant components surface layer activation, which consists of monitoring changes in gamma-ray emission from activated components. It has been field-tested in plant applications, and a commercial on-line system is now available.

38803 Anon. Mr. Roentgen's Rays: the birth of radiography for nondestructive evaluation M R S Bul le t in , Vol. 13, No. 4, p. 53 (Apr . 1988)

A brief history of x-ray radiography is given from Roentgen's discovery of X-rays in 1895 and the development of X-ray tubes by Coolidge in 1913. Radiography was critically important for weld detection for wartime aircraft and ships and later for ensuring weld integrity on nuclear pressure vessels. The development of gamma radiography in the 1950s permitted portable devices to be developed. Late X-ray and gamma-ray films became availabe. X-ray radiography is widely used today to inspect the composition and thickness of many types of materials.

38783 Edwards, I. ROV-Mounted radiographic flooded member detection system U n d e r w a t e r Sys tems Des ign , Vol. 10, No. 3, pp. 29-33 (May/Jun . 1988)

Underwater structures can be examined for defects using Flooded Member Detection (F.M.D.). FMD tests are fast enough to allow whole structures to be inspected rather than suspected problem nodes only. Personnel and other costs are minimized by using Remotely Operated Vehicles (R.O.V.) including a new tool or "claw". A new FMD technique based on gamma radiography is proving successful and more accurate than previously used ultrasonic methods.

38229 Holt, R.S.; Cooper, M.J. Non-destructive examination with a Compton scanner Bri t ish Jou rna l of N o n d e s t r u c t i v e Test ing, Vol. 30, No. 2, pp. 75-811 (Mar . 1988)

A Compton scanner, which uses a 10 Curies Cesium-137 radioisotope source of 662 keV gamma-rays to form 2-dimensional images of bulk samples from the 90 deg. scattered signal, has been employed to investigate systematically the visibility of embedded voids and inclusions of various sizes located in different positions. The results were compared with computer simulations which have demonstrated that a single scattering approximation is adequate to describe the contrast observed. In a separate experiment an X-ray source was used to measure the contrast of voids with WKalpha, WKbem characteristic and bremsstrahlung radiation. The results show that the constrast is effectively independent of the energy, or range of energies used, and can be predicted from the same model. As a rough rule-of-thumb, voids remain visible down to a typical dimension of half the beam width.

3821)8 Domanus, J. C. Recording radiographic images on nitrocellulose f i lm in neutron radiography of nuclear reactor fuel Riso Na t iona l L a b o r a t o r y , R o s k i l d e ( D e n m a r k ) , RISO-M-2654 , 22 pp. (Aug . 1987)

Nitrocellulose film, insensitive to X- and gamma-rays (as well as visiblc light), is especially suitable for neutron radiography of spent nuclear reactor fuel, which itself is a source of high-intensity gamma- radiation. As nitrocellulose film is also insensitive to neutrons a converter is necessary to convert neutrons to alpha particles, which in turn are able to produce a radiographic image on the film. This image, in the form of minute pits in the film, must thereafter be made visible by etching the nitrocellulose film to thereby enlarge the pits so much as to produce a visible image on the film. After a short description of neutron radiography facilities at various reactor types three methods of producing neutron radiographs are explained (direct, transfer and track-etch). Nitrocellulose film and neutron-to-alpha converters used with it are described. Radiographic image quality of this film is compared with that of silver halide film. A similar comparison is made of the accuracy of dimensional measurements from neutron radiographs.

38207 Bridge, B.; Harirchian, F.; lmrie, D.C.; Mehrabi, Y.: Meragi, A.R. E x p e r i m e n t s in Compton scatter imaging of materials with wide- ranging densities using a low activity gamma source N D T In t e rna t i ona l , Vol. 20, No. 6, pp. 339-346 (Dec. 1987)

A low-activity Compton scatter imaging device employing a 1.4 mCi 133Ba gamma source has been used to detect 6 mm diameter voids in materials of very different densities and structural types. Two- dimensional histogram images have been obtained of sections of steel, steel covered with simulated marine growth, medium-density polyethylene and an inorganic ceramic cement, all containing 6 mm diameter simulated voids. The image contrast is large enough to differentiate these voids from statistical noise in runs of reasonable duration for practical source intensities, therefore making the technique promising for a variety of applications to small component inspection. The images obtained arc corrected for the effects of photon attenuation and in one case the image has been compared with a non-corrected one.

38203 Ghosh, J.K.; Panakkal, J.P.; Chandrasekharan, K.N.; Roy, P.R. A combined X-radiography-gamma-autoradiography (XGAR) tech- nique for characterisation of welded nuclear fuel pins

l l t h Wor ld Confe rence on Nondes t ruc t i ve Tes t ing , Los Vegas , N e v a d a ( U n i t e d Sta tes) , 3-8 Nov. 1985. Vol. 2, pp. 1174-1180. Tay lo r Publ ishing Co . , Da l l a s (1985).

Nuclear fuel pins undergo inspection at various stages of fabrication to ensure that they conform to specifications. A typical nuclear fuel pin containing fuel pellets is closed at both ends by welding end plugs. There is always a need for a final inspection step to guarantee that the end product does not suffer from any major deviation. The correct loading of all internal components, enrichment of fuel pellets and freedom from plutonium agglomerates particularly, in plutonium bearing fuels can be assured by employing this final nondestructive test on the finished fuel pins. A combined X-radiography-gamma auto radiography (XGAR) technique has been successfully employed in evaluating all the above mentioned characteristics during the inspection of experimental thermal and fast reactor fuel pins. This paper describes the experimental techniques used in detail and presents typical examples of anomalies observed during the inspection of experimental mixed oxide (U,Pu)O 2 fuel and mixed carbide (U,Pu)C fuel fabricated in this centre.

37979 Heald, J.D. Method and apparatus for crack detection and characterization U.S. Patent No. 4,680,470 (14 Jul . 1987)

A new method for nondestructive detection and characterization of defects in radioactively contaminated structures is described. A gamma ray detector scans the surface of the sample and signals are recorded at various angles relative to the sample's surface. Comparing the amounts of radiation emitted at each angle and point allows a graphical representation of the anomaly to be drawn up.

37912 Bridge, B.; Harirchian, F.; Mehrabi, Y.; Meragi, A.R. Gamma-ray absorption and its effects on images obtained from a low strength Compton device Nondes t ruc t i ve Tes t ing C o m m u n i c a t i o n s , Vol. 3, No. 4/5, pp. 127-138 (1987)

A forward Compton scatter gamma-ray imaging device is briefly described and the gamma-ray absorption in mild-steel samples containing voids is discussed. It is shown ttqat in general any corrections for absorption invariably produces artifacts in the images of regions around voids, although this phenomenon is less significant for smaller voids and less dense materials.

37910 Lincoln, A. Engines through the looking glass Science and Bus iness L ink-up , pp. 17-19 (Oct . 1987)

Positron emission tomographic devices (P.E.T.s) have a number of engineering as well as medical applications (such as the study of liquid flow, engine performance and cancer detection). Accurate multiwire proportional counters detect the gamma radiation given off by positrons and results are microprocessed to produce a P.E.T. scanning device.

37907 Varnavskii. V.V.; Zol'nikov, P.P. Induced radioactivity of steel components in indus t r i a l f law inspec t ion with electron accelerators Soviet Journa l of Nondes t ruc t ive Test ing, Vol. 23, No. l , pp. 29-35 (Sep. 1987)

The results are presented of experimental investigations of the characteristics of gamma radiation of induced radioactivity of steel components and also of structural members of the accelerator/flaw detector. Semiempirical equations are proposed for determining the holding time of inspected components and the betatron which take into account the focusing distance, exposure time, and braking radiation intensity.

37869 Spyrou, K. ; Spyrou, N.M. Imaging with neutrons in transmission tomography Neu t ron R a d i o g r a p h y , Proceed ings of the Second Wor ld Confe r ence , Paris (France) , 16-21) Jun. 1986. pp. 719-728. D. Re ide l Publ i sh ing C o m p a n y

Reconstructive tomography was carried out using multiple neutron radiographs of an object as well as multiple projections of the transmitted neutron beam through the object using an He-3 proportional counter. Gamma-ray transmission tomography employing the 60 kcV gamma- ray line of a well-collimated Am-241 source was also applied to the same object. A 35 mm camera was modified to incorporate a neutron converter so that sequential radiographs could be obtained without disturbing the geometrical arrangement between beam, object and recording medium. A conventional converter/film combination, in one single cassette, was also used. Results show that the technique using the collimated He-3 neutron detector provides tomographic images which arc superior in terms of contrast and noise due to statistical fluctuation.

37843 Jin Si-Kwon; Whiltemore. W.L. Neutron radiography with Van De Graaff neutron source Neut ron R a d i o g r a p h y , Proceed ings of the Second Wor ld Confe r ence , Paris (France) , 16-20 Jun. 1986. pp. 191-198. D. Re ide l Publ i sh ing C o m p a n y

An neutron radiograph (NR) system was installed in 1983 to produce routine high quality neutron radiographs with a Van de Graaff neutron source. Two divcrgcnt beam ports cmcrgc on opposite sides of the moderator. Two shielded walk-in cells are provided for radiography. Special features of the moderator are of interest. The moderator is especially contoured and constructed to permit at least two modes of operation: in one, a high quality NR beam is produced with a

1 56 NDT& E International June 1 991