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| Program name | Package id | Status | Status date |
|---|---|---|---|
| ACHILLES | CSNI1015/01 | Arrived | 01-AUG-2001 |
Machines used:
The most important features of the Achilles rig were the shroud vessel, which contained the test section, and the downcomer. These may be thought of as representing the core barrel and the annular downcomer in the reactor pressure vessel.
The test section comprises a cluster of 69 rods in a square array within a circular shroud vessel. The rod diameter and pitch (9.5 mm and 12.6 mm) were typical of PWR dimensions. The internal diameter of the shroud vessel was 128 mm. Each rod was electrically heated over a length of 3.66 m, which is typical of the nuclear heated length in a PWR fuel rod, and each contained 6 internal thermocouples. These were arranged in one of 8 groupings which concentrated the thermocouples in different axial zones.
The spacer grids were at prototypic PWR locations. Each grid had two thermocouples attached to its trailing edge at radial locations. The axial power profile along the rods was an 11 step approximation to a "chopped cosine". The shroud vessel had 5 heating zones whose power could be independently controlled .
The Achilles experiments investigated the heat transfer in the core of a Pressurised Water Reactor during the reflood phase of a postulated large break loss of coolant accident. The results provided data to validate codes and to improve modelling.
Different types of experiments were carried out which included single phase cooling, reflood under low flow conditions, level swell and reflood under high flow conditions. Three series of experiments were performed. The first and the third used the same test section but the second used another test section, similar in all respects except that it contained a partial blockage formed by attaching sleeves (or "balloons") to some of the rods.
Achilles Rig.
The programme includes the following types of experiments:
on an unballooned cluster:
single phase air flow
low pressure level swell
low flooding rate reflood
high flooding rate reflood
on a ballooned cluster containing 80% blockage formed by 16 balloon sleeves
single phase air flow
low flooding rate reflood
Keywords: heat transfer, loss-of-coolant accident, pwr reactors, reflooding.
