1. Name of Experiment:
 ------------------
 JANUS Phase 8 (1990)

2. Purpose and Phenomena Tested:
 ----------------------------
 Neutron transport in regions of mild steel and sodium. The
 purpose was to test the prediction of neutron penetration through
 sodium when the incident spectrum was typical of that
 emerging from a fast reactor.

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 fission plate is followed by four mild steel slabs, six tanks of sodium,
 two slabs of stainless steel and a backing shield of polythene and lead.
 This gives a thickness of 280 cm sodium preceded by 17.85 cm mild steel.
 The initial region of mild steel modifies the spectrum of neutrons
 incident upon the stainless steel to make it closer to that leaving a fast reactor.

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

 Typical Counting Systematic
 Detector Diameter Thickness Mass System Absolute
 (mm) (mm) (g) Calibration
 (uncertainty)
----------------------------------------------------------------------
 Mn55(n,g)/Cd 12.7 0.15 0.12 NaI 1.5%

 Au197(n,g)/Cd 12.7 0.05 0.12-0.13 NaI 0.9%

 Rh103(n,n') 12.7 0.015 0.20 NaI 3.0%

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

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

 The Mn and Au foils were contained in cadmium boxes of thickness
 0.05 inches.


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

 Measurements of the reaction rates for S32(n,p)P32, Rh103(n,n')Rh103m,
 and Au197(n,g)Au198 Under Cd were made at locations between the mild
 steel plates and between the tanks of sodium. The reaction rates for
 Mn55(n,g)Mn56 Under Cd were also measured in the region of sodium.
 Lateral scans were made with the four detectors at selected positions
 between the tanks of sodium.

 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 by making measurements with the plate both fuelled and unfuelled.
 For the low energies the background varied from 27% close to the fission
 plate to 2% at deep penetrations. For the threshold detectors the
 corrections were 1% close to the plate increasing to 13% at the last
 sodium tank.

 Calculations were carried out with the Monte Carlo code McBEND Version 9A
 [3].
 Input data for McBEND calculation of JANUS-1 (included in SINBAD-JANUS-1)
 could serve as a starting point to prepare the JANUS-8 input.

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

 None

7. Author/Organizer
 ----------------

 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] I. J. Curl,
 "CRISP - A Computer Code to Define Fission Plate Source Profiles",
 RPD/IJC/934.
 [2] J. Butler et al., "The PCA Replica Experiment, Part 1. Winfrith
 Measurements and Calculations", AEEW-R1763
 [3] Locke H. F., "The Analysis of JANUS Phase 8 Using the Monte Carlo Code
 MCBEND", AEA-RS-1182.
 [4] A. Avery, JANUS Phase 8 Benchmark Experiment Data for Inclusion in
 the SINBAD Database, Jan. 1998

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

 DETAILED FILE DESCRIPTIONS
 --------------------------

 Filename Size[bytes] Content
 ---------------- ----------- -------------
 1 jan8-abs.htm 9.432 This information file
 2 jan8-exp.htm 30.989 Description of Experiment
 3 FIG-1.TIF 135.496 Figure 1: The ASPIS Mobile Shield Tank in the NESTOR 
   Cave C (high quality)
 4 FIG-2.TIF 247.647 Figure 2: Schematic Side Elevation of the Experimental
   Viewed Looking Towards the NESTOR Cave (high quality)
 5 FIG-3.TIF 103.528 Figure 3: Sodium Tank Assembly Diagram (high quality)
 6 FIG-4.TIF 152.450 Figure 4: The Enriched U/Al Alloy Fission Plate 
   (high quality)
 7 FIG-5.TIF 200.259 Figure 5: Details of the Fuel Loading Pattern When
   Viewed Looking Towards the NESTOR Cave (high quality)
 8 FIG-6.TIF 150.639 Figure 6: The Individual U/Al Alloy Fuel Element 
   (high quality)
 9 FIG-7.TIF 171.708 Figure 7: The Fuel Element Configuration and Manganese 
   Foil Positions (high quality)
10 FIG-8.TIF 112.589 Figure 8: Mesh Boundaries for the Fission Plate Source 
   (high quality)
11 FIG-9.TIF 132.728 Figure 9: Location of Fission Discs in the Demountable 
   Fuel Element (high quality)
12 FIG-10.TIF 275.746 Figure 10: Measurement Locations for JANUS Phase 8 
   (high quality)
13 FIG-1.gif 19.268 Figure 1: The ASPIS Mobile Shield Tank in the NESTOR 
   Cave C (preview)
14 FIG-2.gif 19.827 Figure 2: Schematic Side Elevation of the Experimental
   Shield of the JANUS Phase 8 in the ASPIS Trolley (preview)
15 FIG-3.gif 12.555 Figure 3: Sodium Tank Assembly Diagram (preview)
16 FIG-4.gif 15.305 Figure 4: The Enriched U/Al Alloy Fission Plate (preview)
17 FIG-5.gif 19.474 Figure 5: Details of the Fuel Loading Pattern When
   Viewed Looking Towards the NESTOR Cave (preview)
18 FIG-6.gif 15.823 Figure 6: The Individual U/Al Alloy Fuel Element (preview)
19 FIG-7.gif 19.019 Figure 7: The Fuel Element Configuration and Manganese 
   Foil Positions (preview)
20 FIG-8.gif 14.299 Figure 8: Mesh Boundaries for the Fission Plate Source 
   (preview)
21 FIG-9.gif 13.917 Figure 9: Location of Fission Discs in the Demountable 
   Fuel Element (preview)
22 FIG-10.gif 26.447 Figure 10: Measurement Locations for JANUS Phase 8 (preview)
23 janus8.pdf 5.179.627 Reference


 File JAN8-exp.htm contains the following tables:
 One table (1) of axial dimensions and (2) of material specifications, two
 tables (3 & 4) describing the source distribution, four tables (5-8) of the
 measured reaction rates and four tables (9-12) showing the lateral scans.

 Figures describing the geometry of the experiment and Tables A1 to A19 are
 included in TIFF5 compressed image format.