第一届新型反应堆安全及发展研讨会，中国 兰州，2013.10.10～12
VENUS-1#装置脉冲源实验分析
谢金森（xiejinsen@139.com）
南华大学
NEAL-Nuclear Energy & Application Lab, University of South China
第一届新型反应堆安全及发展研讨会
CONTENTS
 Background and Purpose
 Core Composition & PNS Experiment of VENUS-1#
 Preliminary Results from PNS Experiment
 Simulation of PNS Experiment on Certain Condition
 Comparison of Simulated and Experimental Results
 Summary & Future Suggestions
第一届新型反应堆安全及发展研讨会
BACKGROUND AND PURPOSE
Background
 R&D on Accelerator Driven System for MA and LLFP Transmutation
 Supported by two “973” Projects
 The World-first Fast-Thermal Coupled ADS core- VENUS-1# has
been built in 2005;
 Abundant research works on Sub-critical neutronics have been
carried out on VENUS-1#.
 Supported by Chinese Academy of Science
 5MWt~10MWt Pb-Bi cooled ADS core will be built (First-step,
Critically Operation; Second-step, Accelerator coupling with subcritical core );
Although massive meaningful results has been obtained, some
issues on Sub-criticality measuring still exist.

第一届新型反应堆安全及发展研讨会
BACKGROUND AND PURPOSE
Background
 To support the development of sub-criticality measuring technique,
Pulsed Neutron Source experiments on VENUS-1# has been performed
2005, VENUS-1# was coupled with CPNG (CIAE Pulsed Neutron
Generator), five different Sub-critical levels;

2007, the first PNS experiment analysis work was published (Thesis of
Shanghai Jiaotong Univ.) ;

2011,
PNS experiment simulation work was performed, three different
Sub-critical levels, D-T, 252Cf, Am-Be neutron sources(Thesis of CIAE).
 All the above works indicate: Prompt neutron attenuation constants
depend on detectors’ locations & driven source energy.
第一届新型反应堆安全及发展研讨会
BACKGROUND AND PURPOSE
Fuel pins of
Thermal
blanket
2046
2022
1998
1962
1926
Prompt neutron attenuation constants
Detector_6th
Detector_10th
Detector_R
Detector_S
1627.6±22.4 (1)
795.33 (2)
1716.2±26.4
840.02
1771.8±41.4
960.64
1823.6±14.4
967.85
1928.8±14.4
1119.50
1705.0±25.0
763.76
1702.0±14.4
832.11
1888.0±48.0
985.87
1922.4±16.4
985.87
1946.4±11.9
1076.40
2495.4±67.8
709.70
2426.2±23.4
758.17
3056.6±83.2
879.90
3868.8±32.2
921.40
4311.4±18.2
1076.40
1350.4±36.4
-1576.4±17.9
-1671.2±62.0
-1646.6±17.5
-1662.4±33.6
--
(1) Experimental results of CIAE;
(2) MC simulation results of SJTU.
第一届新型反应堆安全及发展研讨会
BACKGROUND AND PURPOSE
Purpose
 Confirm the results from former researches;
 Feasibility study of PNS method on Fast-thermal coupled core;
 Investigate the potentially special phenomenon of Fast-thermal
coupled core under pulsed neutron condition.
第一届新型反应堆安全及发展研讨会
CORE COMPOSITION & PNS
EXPERIMENT OF VENUS-1#
Core Composition
Main parameters of VENUS-1#
 External source region: coupled
with accelerator, neutron tube, or
isotopic neutron source;
 Fast spectrum blanket: natural
uranium pins + aluminum block, 10
layers;
 Thermal spectrum blanket : 3wt%
uranium pins+ CH2 block, 15 layers
maximum;
 Reflector: CH2 block, 200mm thick;
Shield: CH2+B, 200mm thick;
第一届新型反应堆安全及发展研讨会
CORE COMPOSITION & PNS
EXPERIMENT OF VENUS-1#
CPNG neutron generator
(CIAE Pulse Neutron Generator )
Main parameters of CPNG
 Type: Cockcroft-Walton
 High voltage: 200~600kV
 Pulse beam frequency: 50~200Hz
 Pulse width:1~5us
第一届新型反应堆安全及发展研讨会
CORE COMPOSITION & PNS
EXPERIMENT OF VENUS-1#
Experimental conditions & instrument system
Detectors
Sub-criticalities:
adjusted by thermal fuel pin loading;
1926, 1962, 1998, 2022, 2046;
Detectors:
3 3He tubes (6th, 10th layer of fast blanket
& reflector);
1 BF3 tubes (Shield)
Electronic system: 60 multi-channels; 50us/channel;
Data collection:
3 groups data; 105 pulses;
statistical errors for first several channels < 1%;
第一届新型反应堆安全及发展研讨会
6th
10th
R
0.12
S
Thermal blanket with 1926 fuel pins
0.18
0.17
0.16
0.15
0.14
0.13
0.12
0.11
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00
-0.01
Normarized Neutron Count Rate
Normarized Neutron Count Rate
PRELIMINARY RESULTS FROM
PNS EXPERIMENT
6th
10th
R
S
0.10
0.08
0.06
0.04
0.02
0.00
0
10
20
30
40
50
0.17
0.16
0.15
0.14
0.13
0.12
0.11
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00
-0.01
Normarized Neutron Count Rate
20
30
40
50
20
0.12
30
60
0
10
20
30
0.08
0.06
0.04
0.02
0.00
20
30
Chanel Number
40
40
Channel Number
6th
10th
R
S
0.10
10
50
60
6th
10th
R
S
Thermal blanket with 2022 fuel pins
Thermal blanket with 2046 fuel pins
0
40
0.070
0.065
0.060
0.055
0.050
0.045
0.040
0.035
0.030
0.025
0.020
0.015
0.010
0.005
0.000
Channel Number
Normarized Neutron Count Rate
10
10
Channel Number
6th
10th 0.085
R
0.080
S
0.075
Thermal blanket with 1962 fuel pins
0
0
60
Channel Number
Normarized Neutron Count Rate
Thermal blanket with 1998 fuel pins
50
60
50
Fuel pins
of Thermal
blanket
Prompt neutron attenuation constants
6th
10th
R
S
2046
1627.6±22.4
1705.0±25.0
2495.4±67.8
1350.4±36.4
2022
1716.2±26.4
1702.0±14.4
2426.2±23.4
1576.4±17.9
1998
1771.8±41.4
1888.0±48.0
3056.6±83.2
1671.2±62.0
1962
1823.6±14.4
1922.4±16.4
3868.8±32.2
1646.6±17.5
1926
1928.8±14.4
1946.4±11.9
4311.4±18.2
1662.4±33.6
60
第一届新型反应堆安全及发展研讨会
PRELIMINARY RESULTS FROM
PNS EXPERIMENT
Discussion on the experimental results
 Prompt neutron attenuation constants show strong spatial
dependence;
 The attenuation constants obtained by detectors show large
discrepancies;
 The experimental results conflict with theory of experimental reactor
physics (lumped parameter Point Reactor Dynamics) ;
Which attenuation constant should be used as a sub-critical indicator,
or how to make spatial corrections.
第一届新型反应堆安全及发展研讨会
SIMULATION OF PNS EXPERIMENT
ON CERTAIN CONDITION
Theoretical considerations
 Harmonics neutron flux seriously affects detector responses in deep
sub-critical condition (both static & transient ) ;
 For Fast-thermal coupled system, typical prompt neutron life time is
10-5 second, width of multi-channel should be correspond to the
condition for better inferring of harmonics (can be easily realized in
simulation);
 To obtain the prompt neutron attenuation constants (fundamental
mode), harmonics should be filtered.
第一届新型反应堆安全及发展研讨会
SIMULATION OF PNS EXPERIMENT
ON CERTAIN CONDITION
Theoretical considerations
 In transient conditions, neutron flux can be expressed as:
 (r , t )   (r )T (t )
 Consider Alpha Eigen-value problem, neutron density in PNS:
N ( r , t )  S ( r )e

S (r )e t
t
 A0 (r )0 (r )e
t

  Ai (r )i (r )e i t
i 1
Contribution of external source
t
 A0 (r)0 (r)e
Contribution of fundamental Alpha mode
 Ai (r )i (r )e
it
Contributions of the ith harmonic Alpha modes
第一届新型反应堆安全及发展研讨会
SIMULATION OF PNS EXPERIMENT
ON CERTAIN CONDITION
Theoretical considerations
 Relationship of each attenuation constant:
  1  2    i  
 When harmonics and source contribution disappeared:
N (r1 , t )
A (r ) (r )
 0 1 0 1  const
N (r2 , t ) t  t
A0 (r2 )0 (r2 )
0
第一届新型反应堆安全及发展研讨会
SIMULATION OF PNS EXPERIMENT
ON CERTAIN CONDITION
Methodology of simulation
 Simulation conditions:

MCNP4CTM selected as PNS simulation code;

2046 thermal fuel pins loading for comparison with experiment;

Multi-channel width set as 5us for better inferring harmonics effect,
totally 600 channels (0~3000us, the same as experiment);
 Data processing technique:

Detector response of R selected as benchmark;

Relative responses to R used for fundamental attenuation time
region search;
第一届新型反应堆安全及发展研讨会
SIMULATION OF PNS EXPERIMENT
ON CERTAIN CONDITION
Simulation results
6th
10th
R
S
2
10
6th/R
10th/R
S/R
1000
1
0
10
S
-1
10
10th
R
-2
10
-3
10
6th
Relatived Neutron Count rate
100
-1
Relative Neutron Count(s )
10
Fundamental decay mode
10
1
0.1
-4
10
0
100
200
300
400
500
600
Time(5s)
Simulated detector responses
0.01
0
50000
100000
150000
200000
250000
300000
-8
Time(10 s)
Simulated relative detector responses
第一届新型反应堆安全及发展研讨会
SIMULATION OF PNS EXPERIMENT
ON CERTAIN CONDITION
Simulation results
 Detector responses in time interval 500~3000us selected as
fundamental attenuation constant fitting
Detectors
Alpha values
Correlation
coefficients
6th
10th
R
S
1430.30±8.71 1436.76±3.99 1436.60±3.49 1417.35±1.12
0.99087
0.99809
0.99853
0.99984
第一届新型反应堆安全及发展研讨会
COMPARISON OF SIMULATED AND
EXPERIMENTAL RESULTS
Comparison of detector responses
 The simulated data use the same channel width of experiment;
 Quite different attenuation trends observed.
6th
10th
R
S
10
Neutron count rate
0.1
Normarized Neutron Count Rate
100
1
0.1
0.01
6th
10th
R
S
0.01
1E-3
1E-3
0
10
20
30
40
Channel number
Simulated data
50
60
0
10
20
30
40
50
Channel Number
Experimental data
60
第一届新型反应堆安全及发展研讨会
COMPARISON OF SIMULATED AND
EXPERIMENTAL RESULTS
Comparison of Alpha constants
 Original experiment data;
 harmonics filtered simulated data;
 harmonics filtered experimental data.
Normarized Neutron Count Rate
6th
10th
R
S
Original Exp. data
0.1
6th
10th
R
S
Original
Experimental
data
1627.6±22.4
1705.0±25.0
2495.4±67.8
1350.4±36.4
Harmonics
filtered
Experimental
data
1664.2±55.8
1521.0±30. 2
2902.0±78. 7
1385.6±59.0
Harmonics
filtered
simulated
data
1430.30±8.71
1436.76±3.99
1436.60±3.49
1417.35±1.12
0.01
1E-3
0
10
20
30
40
50
60
Channel Number
B
C
D
E
Harmonics filtered Exp.
Data(500~3000us)
0.1
Neutron Count rates
Alpha values
0.01
1E-3
10
20
30
40
Channels(50s/channel)
50
60
第一届新型反应堆安全及发展研讨会
COMPARISON OF SIMULATED AND
EXPERIMENTAL RESULTS
Comparison of Alpha constants
 original experimental data;
 harmonics filtered simulated data;
 harmonics filtered experimental data.
3000
2800
The Alpha indicated by detector 10th has
been improved;

2600
Alpha values
2400
Original experiment Alpha
Simulated Alpha with harmonics filtering
Original exp. data with harmonics filtering
2200
2000
The Alpha value obtained by detector S
is closest to simulated one;

1800
The Alpha value of detector R still show
big discrepancy.
1600

1400
1200
6th
10th
Detector label
R
S
第一届新型反应堆安全及发展研讨会
COMPARISON OF SIMULATED AND
EXPERIMENTAL RESULTS
Verification of the simulated Alpha
 In one neutron generation time, the prompt neutron population:
T (l )  T (0)k p
 For sub-critical system:
T (l )  T (0)el
 Relationship between kp and Alpha:
k p  e l
kp
6th
10th
R
S
From α
0.92492
0.92460
0.92461
0.92558
0.94117±0.00266
MCNP
△kp*
-1.727%
1.761%
1.760%
1.656%
第一届新型反应堆安全及发展研讨会
SUMMARY & FUTURE SUGGESTIONS
Summary
 Using relative neutron count rates as an indicator, time region for
fundamental Alpha mode decay can be easily obtained (a harmonics
filtering technique);
 The simulated data with harmonics filtering technique give a spatially
independent prompt neutron attenuation constants;
 Some Alpha values from experiment is improved by harmonics filtering,
however some other values are worsen.
第一届新型反应堆安全及发展研讨会
SUMMARY & FUTURE SUGGESTIONS
Suggestions
 Since the big discrepancy between experiment and simulation, as well
as the short neutron life time and harmonics influence in the Fast-thermal
couple ADS core, more rapid electronics data collection system should be
used in future PNS experiment;
 Although the harmonics filtering technique show the capability for Alpha
measuring, the accuracy of calculated prompt neutron generation time
plays a key role in verification work (consider the coupling between
external neutron source region, fast blanket, thermal blanket and reflector,
the effective generation time should be introduced, as well as its
calculation theory)
第一届新型反应堆安全及发展研讨会
Thanks for your attention!