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Winfrith Graphite Benchmark Experiment (ASPIS)

1. Name of Experiment:
 Winfrith Graphite Benchmark Experiment (ASPIS)

2. Purpose and Phenomena Tested:
 Determination of the accuracy of methods used to calculate the neutron
 component of nuclear heating. Threshold reaction rates were measured up
 to 0.7 m in graphite.

3. Description of the Source and Experimental Configuration:
 The source is a fission plate constructed of 93% enriched uranium
 aluminium alloy driven by a thermal flux from the extended graphite
 reflector of the NESTOR reactor. The energy spectrum of the source is
 the one of neutrons emitted from the fission of U-235. The absolute
 source strength is determined by fission product counting and the spatial
 distribution via detailed low energy flux mapping with activation
 The graphite assembly had lateral dimensions 180 cm x 190 cm and total
 length was 177.32 cm. It was built from graphite block of various sizes.
 The concrete of the approximate thickness 76 cm encases the whole assembly.
 The detectors were placed in the central block in the cylindrical plug,
 inserted in 6.45 cm radius hole along the major axis of the block.

4. Measurement System and Uncertainties:
 The detectors used were:

 Detector Diameter Thickness Mass Counting Systematic
 (mm) (mm) (g) System Error (%)

 Al-27(n,alpha) 50 3.1 16.72 Ge detector 4.0

 S-32(n,p) 38.1 2.41 5 Plastic scint. 4.0

 In-115(n,n') 38 1.63 12.79 GeLi detector 3.0

 Rh-103(n,n') 12.7 0.015 0.20 NaI 3.0

 The uncertainties (1 sigma) may be taken as uncorrelated, and derive
 essentially from the absolute calibration of the counting system.

5. Description of Results and Analysis:

 Detector activation measurements were carried out at several graphite
 distances: 0, 5, 10, 15, 20, 30, 40, 50, 60, 70 cm. The positions
 correspond approximately to the fission plate axis. Not all detectors
 were placed in all positions.
 The results were corrected for the background responses due to the NESTOR
 core. They were measured for Al-27, S-32 and Rh-103. For In115 those for
 Rh-103 were assumed.
 Calculations were carried out with the Monte Carlo code McBEND and the
 discrete ordinates code DOT 3.5.
 The corresponding input to the 2-D discrete ordinates transport code
 DOT-3.5 is provided.

6. Special Features:


7. Author/Organizer
 Experiment and analysis:
 M.D. Carter, P.C. Miller, A. Packwood:
 AEA Technology
 WINFRITH, Dorchester
 Dorset DT2 8DH

 Compiler of data for Sinbad:
 I. Kodeli
 OECD/NEA, 12 bd des Iles, 92130 Issy les Moulineaux, France

 Reviewer of compiled data:
 Alan F. Avery
 Reactor Physics, Shielding and Criticality Department , AEE Technology
 WINFRITH, Dorchester
 Dorset DT2 8DH

8. Availability:


9. References:

 [1] M.D. Carter, P.C. Miller, A. Packwood,
 The ASPIS Graphite Benchmark Experiment. Part 1 - Experimental Data
 and Preliminary Results, NEACRP-A-630 (1984)
 [2] N. Sasamoto, K. Sakurai, A. Tsubosaka, H. Narita, M. Takemura,
 K. Hayashi, Analysis of the ASPIS Graphite Benchmark Experiment with
 Discrete Ordinates and Monte Carlo Codes,
 NEACRP Specialists' Meeting on Shielding Benchmarks, Paris (1986).
 [3] Alan F. Avery, AEA-RS-5628, private communication.
 [4] G. A. Wright, A. Avery, M. J. Grimstone, H. F. Locke, S. Newbon,
 Benchmarking of the JEFF2.2 Data Library for Shielding Applications,
 Proceedings, 8th International Conference on Radiation Shielding,
 April 24-28, 1994, Arlington, Texas, U.S.A., vol.2, p.816.

10. Data and Format:

 Filename Size[bytes] Content
 ---------------- ----------- -------------
 1 ASC-ABS.HTM 7.462 This information file.
 2 ASC-EXP.HTM 20.668 Description of Experiment.
 3 dot35.INP 4.684 2-D Model for Sn code DOT-3.5.
 4 ASPC-1V.TIF 27.464 Figure 1: Cross-section of the ASPIS graphite 
   benchmark experiment. (high quality)
 5 ASPC-2V.TIF 17.362 Figure 2: Detail of the fission plate.(high quality)
 6 ASPC-3V.TIF 17.696 Figure 3: Section through the ASPIS graphite 
   benchmark model. (high quality)
 7 ASPC-4V.TIF 16.136 Figure 4: RZ geometry of the ASPIS graphite 
   benchmark for the DOT 3.5 calculation. (high quality)
 8 ASPC-1V.gif 20.266 Figure 1: Cross-section of the ASPIS graphite 
   benchmark experiment. (preview)
 9 ASPC-2V.gif 12.183 Figure 2: Detail of the fission plate. (preview)
10 ASPC-3V.gif 14.797 Figure 3: Section through the ASPIS graphite
   benchmark model. (preview)
11 ASPC-4V.gif 11.482 Figure 4: RZ geometry of the ASPIS graphite 
   benchmark for the DOT 3.5 calculation. (preview)
12 WIN_C_1.pdf 2.237.854 Reference
13 WIN_C_2.pdf 458.475 Reference
14 WIN_C_3.pdf 789.823 Reference
15 WIN_C_4.pdf 578.980 Reference

 Figures describing the geometry of the experiment are included in
 TIFF file format and GIF (preview) format.

 Tables in Asc-exp.htm:
 one table of axial dimensions and of chemical composition of materials
 present in the configuration, 3 tables describing the source, and
 4 tables of the measured reaction rates.