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CSNI1015 ACHILLES.

ACHILLES, Heat Transfer in PWR Core During LOCA Reflood Phase

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1. NAME OF EXPERIMENT:  ACHILLES.
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2. COMPUTERS
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Program name Package id Status Status date
ACHILLES CSNI1015/01 Arrived 01-AUG-2001

Machines used:

No specified machine
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3. DESCRIPTION OF TEST FACILITY

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 .
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4. DESCRIPTION OF TESTS

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.
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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM: EXPERIMENTAL LIMITATIONS OR SHORTCOMINGS
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6. PHENOMENA TESTED

Heat transfer in the core of a PWR during a reflood phase of postulated large break LOCA.
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7. UNUSUAL FEATURES: SPECIAL FEATURES OF EXPERIMENTS
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8. RELATED OR AUXILIARY PROGRAMS: COUNTERPART EXPERIMENTS
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9. STATUS
Package ID Status date Status
CSNI1015/01 01-AUG-2001 Arrived at NEADB
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10. REFERENCES
CSNI1015/01, included references:
- A. Mason and M.L. Hood:
Data Processing for the Achilles Experiments, AEEW-R 2321 (March 1991)
- P. Dore and K.G. Pearson:
Achilles Ballooned Cluster Experiments, AEA-TRS-1060, AEEW-2590
- K.G. Pearson and M.K. Denham:
Achilles Unballooned Cluster Experiments - Part 1: Description of the Achilles
Rig, Test Section and Experimental Procedures, AEEW-R 2336 (November 1989)
- K.G. Pearson and M.K. Denham:
Achilles Unballooned Cluster Experiments - Part 2: Single Phase Flow
Experiments, AEEW-R 2337 (May 1989)
- K.G. Pearson and M.K. Denham:
Achilles Unballooned Cluster Experiments - Part 3: Low Flooding Rate Reflood
Experiments, AEE2-R 2338 (June 1989)
- K.G. Pearson and M.K. Denham:
Achilles Unballooned Cluster Experiments - Part 4: Low Pressure Level Swell
Experiments, AEEW-R 2339 (June 1989)
- P. Dore and M.K. Denham:
Achilles Unballooned Cluster Experiments - Part 5: Best Estimate Experiments,
AEEW-R 2412 (July 1990)
- P. Dore and D.S. Dhuga:
Achilles Unballooned Cluster Experiments - Part 6: Flow Distribution
Experiments, AEA-RS-1064 (December 1991)
- B.J. Holmes:
ISP 25 Comparison Report AEA-TRS-1043 (February 1991) NEA/CSNI/R(91)11
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11. TEST DESIGNATION

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
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12. PROGRAMMING LANGUAGE(S) USED
No specified programming language
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15. ESTABLISHMENT

AEA Technology
Winfrith Technology Centre
Dorchester DT2 8DH
United Kingdom
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16. MATERIAL AVAILABLE
CSNI1015/01
Test data and associated data processing software
Documentation in PDF format
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17. CATEGORIES
  • Y. Integral Experiments Data, Databases, Benchmarks

Keywords: heat transfer, loss-of-coolant accident, pwr reactors, reflooding.