Abstracts and Available Papers Presented at the
2002 International RERTR Meeting

LEU WWR-M2 FUEL QUALIFICATION

K.A. Konoplev, R.G. Pikulik, A.S. Zakharov, L.V. Tedoradze, G.V. Paneva, D.V.Tchmshkyan

Petersburg Nuclear Physics Institute of Russian Academy of Sciences

PNPI, OrlovaRoscha, Gatchina, 188300, Russia

ABSTRACT

LEU WWR-M2 fuel elements have been developed for supplies from Russia abroad. They are intended for the use in the pool type research reactors.
The goal of the tests was to obtain data needed for the proof by the manufacturer of its warranty on the fuel element performance. As a representative amount, 5 FA were taken with the 19,75% enrichment. The test was conducted in the WWR-M reactor core in the conditions being close to or somewhat more strict that those specified in the manufacturer-factory’s technical specification. By the main parameter – permissible burning depth – the tests were conducted up to the burning of 75-80% at the factory’s warranty of 40%. In the course of tests, FA were multiply re-loaded into various cells of the core with changes of their thermal loads and the surfase temperature. Thermal loads was in ranges from 20 to 320 kW/l the wall temperature – from 70 to 95^оС. The cooling water velocity was practically constant equal to 4 m/s; the chemical composition of the coolant was also constant. The time of fuel element operation on power was about 400 days, and the full duration of tests took more than 3 years.

A distinctive feature of these tests was systematic quantitative measurements of the FA leak tightness degree in the course of burning. For this purpose, in the course of burning FA were unloaded periodically from the core and loaded into the test loop. In the loop, FA was under the load being somewhat less than that in the core. The ratio of the amount of fission-fragment products coming out from FA into the loop coolant to the amount of fission-fragment products being generated for the same time due to the fission of uranium in FA. This ratio called the non-integrity coefficient (β) was compared with the value permissible for the safe operation of the reactor. Findings coefficients (β) in course of burning also is compared for some different types of fuel.
Even at the maximal achieved burning of 80%, β did not exceed 5.10-6, which is far less that the permissible value and is at the level being typical for the reactor operation.

The tests were stopped at 80% of burning due to inexpedience of deeper burning. As a result, the operability of WWR-M2 fuel elements with the enrichment of less than 20% has been proved not only up to the value of 40% or 60% being required by factory but also to a level being approximately twice as much deeper.
LEU WWR-M2 fuel assemblies are recommended and accepted for serial production.
The work has been performed within the framework of the program of the Ministry of Atomic Energy of the Russian Federation and the US Department of Energy. Financial provision was under ANL and Concern TVEL.

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