1. Name of Experiment:
 ------------------
 18/20 NESDIP-3 Benchmark Experiment (ASPIS) - 1985

2. Purpose and Phenomena Tested:
 ----------------------------
 Neutron transport in a shield simulating the radial shield of a PWR,
 including the cavity region and the backing shield.

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 effective radius of the fission plate is 56 cm and the
 thickness 2 mm. The energy spectrum of the source is that 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 detectors.
 The shield simulates the radial shield of a PWR and consists of 18.32 cm of
 water, 5.5 cm stainless steel plate simulating the thermal shield,
 19.8 cm of water, five mild steel plates giving a thickness of 22.9 cm to
 simulate the pressure vessel, a 29.4 cm cavity region and a backing shield
 of aluminium, water and mild steel.

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

 Typical Counting Systematic
 Detector Diameter Thickness Mass System Absolute Random
 (mm) (mm) (g) Calibration error
 (uncertainty)
----------------------------------------------------------------------------
 Rh103(n,n') 12.7 0.015 0.20 NaI 3.0% 1 - 4%

 S32(n,p) 38.1 2.41 5 Plastic 5.0% 1 - 2%
 Pressed Pellet Scintillator

 S32(n,p) 51 5.6 22 Plastic 5.0% 1 - 2%
 Cast Pellet Scintillator
----------------------------------------------------------------------------

 In addition neutron spectrum measurements were made in the cavity with
 three hydrogen proportional counters and an NE213 scintillator.


5. Description of Results and Analysis:
 -----------------------------------

 Measurements of the reaction rate for S32(n,p)P32 were made between the
 steel plates (thermal shield and reactor pressure vessel regions) and in
 the cavity whilst Rh103(n,n')Rh103m measurements were made in the water
 regions.

 In addition, during all irradiations of activation detectors within the
 shields, three sulphur pellets were placed in locations at the centre of
 the front face of the fission plate to monitor its run-to-run power via
 the S32(n,p)P32 reaction.

 The results were corrected for the background responses due to the NESTOR
 core. Using the hydrogen filled proportional counters of the TNS system
 the correction was found to be around 6(+/-2)% in the RPV and cavity and
 2(+/-2)% and 4(+/-2)% respectively in the first and second water cells.

 Calculations were carried out with the Monte Carlo codes McBEND Version 2
 [3].

6. Special Features:
 ----------------

 None

7. Author/Organizer
 ----------------
 Experiment and analysis:
 I.J. Curl, A K McCracken, P C Miller
 AEA Technology
 WINFRITH, Dorchester
 Dorset DT2 8DH
 UK

 Compiler of data for Sinbad:
 A. Avery,
 Performance and Safety Services Department,
 AEA Technology
 WINFRITH, Dorchester
 Dorset DT2 8DH
 UK

 Reviewer of compiled data:
 I. Kodeli
 OECD/NEA, 12 bd des Iles, 92130 Issy les Moulineaux, France


8. Availability:
 ------------

 Unrestricted

9. References:
 ----------

 [1] M. J. Armishaw, J. Butler, M. D. Carter, I. J. Curl, A. K. McCracken,
 A Transportable Neutron Spectrometer (TNS) for Radiological
 Applications, AEEW-M2365 (1986).
 [2] I. J. Curl,
 CRISP - A Computer Code to Define Fission Plate Source Profiles,
 RPD/IJC/934.
 [3] P. C. Miller,
 A Review of LWR Pressure Vessel Dosimetry and Associated Shielding
 Studies, Proceedings, 7th International Conference on Radiation
 Shielding, Sept. 12-16, 1988, Bournemouth, UK, Vol.1, p.37.
 [4] J. Butler et al., The PCA Replica Experiment, Part 1. Winfrith
 Measurements and Calculations, AEEW-R1763
 [5] M. J. Armishaw et al., NESTOR Shielding and Dosimetry Improvement
 Programme: The Cavity, Nozzle and Coolant Duct Benchmark Blind Test
 Edition, AEEW-M2334 (1986).
 [6] A. Avery, 18/20 NESDIP 3 Benchmark Experiment Data for Inclusion in
 the SINBAD Database (1998)

10. Data and Format:
 ---------------

 Filename Size[bytes] Content
 ---------------- ----------- -------------
 1 nes3-abs.htm 8.518 This information file
 2 nes3-exp.htm 21.484 Description of Experiment
 3 MCBEND.DAT 47.288 MCBEND input data
 4 FIG1.TIF 190.315 Figure 1: Cross-section of the shield (high quality)
 5 FIG2.TIF 91.817 Figure 2: Measurement locations (high quality)
 6 FIG3.TIF 172.931 Figure 3: Schematic diagram of fission plate (high quality)
 7 FIG4.TIF 142.003 Figure 4: Fuel element (high quality)
 8 FIG5.TIF 648.635 Figure 5: Disposition of fuel in fission plate (high quality)
 9 FIG6.TIF 177.046 Figure 6: Positioning of the fission plate (high quality)
10 FIG7.TIF 133.888 Figure 7: Location of fission discs in the fuel element 
   (high quality)
11 FIG1.gif 17.637 Figure 1: Cross-section of the shield (preview)
12 FIG2.gif 18.276 Figure 2: Measurement locations (preview)
13 FIG3.gif 17.737 Figure 3: Schematic diagram of fission plate (preview)
14 FIG4.gif 16.020 Figure 4: Fuel element (preview)
15 FIG5.gif 20.967 Figure 5: Disposition of fuel in fission plate (preview)
16 FIG6.gif 20.248 Figure 6: Positioning of the fission plate (preview)
17 FIG7.gif 13.158 Figure 7: Location of fission discs in the fuel element 
   (preview)
18 M2334.pdf 4.550.823 Reference
19 Nesdip3.pdf 1.468.826 Reference
20 aspis_0.pdf 608.178 Reference

 Tables:
 One table (1) of axial dimensions and (2) of material specifications, one
 table (3) describing the source distribution, and 2 tables (4-5) of the
 measured reaction rates.

 Figures describing the geometry of the experiment are included in
 TIFF5 image format and GIF (preview) format.