Fig. 3-11 In-field radiography inspection by using the Ytterbium-169 irradiator

Fig. 3-12 The picture shows the integrity of welding for the 2.5-mm thick steel plates

Ytterbium-169 (169Yb) radiation source is very useful for the non-destructive testing (NDT) such as thin and tiny steel pipe-line or structural components of the plant systems which are composed of less than about 12-mm thick steel plates or pipes. These sized components were unable to be inspected for faults or cracks by using Iridium-192 gamma source (192Ir). As 169Yb has a relatively short half-life of 32-days and it is therefore necessary to exchange the sources in a short time, the domestic production has been started by the effective use of the JRR-3M and JMTR reactors in JAERI. 169Yb radiography sources are produced on a scale of six-times per annum and 370 GBq (200 sources per batch) per annum. 169Yb features its low gamma radiation energy and small size (1-mm in diameter and 1-mm in length) so the sources are able to take a clear radiographic picture of the cracks or faults of welding of the plant components. Ytterbium-168 targets (20-% enriched) are used in order to make effective neutron irradiation in these reactors. Radiographic inspection is made by the specially designed irradiators in which 169Yb sources are contained as shown in Fig. 3-11. This work is made at the small space parallel with another one, for this device is able to attenuate 1/100 against the gamma ray radiation of the sources by 5-cm thick lead shielding. In the future the application of 169Yb source will be expected to be expanded furthermore for the non-destructive testing of tiny piping and structural thin steel plates of the large scale systems and chemical plants.

Reference H. Yamabayashi, Development of Production Techniques for Ytterbium-169 sources, Radioisotopes, 43 (5), 296 (1994).

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