RRFM 2009 Transactions - European Nuclear Society

2.1 Irradiation Facilities
Brief technical specifications for both the LEU and HEU cores of SLOWPOKE-2 are shown in
Table 1, and highlights the expected increase in performance of the LEU core [2].
Parameters HEU LEU
Maximum operating power 20 kW 20 kW
Maximum operating time at 3 mk 6 hrs 12 hrs
Maximum operating time at 4 mk 16 hrs 24 hrs
Core Life-Time 20 Years 40 Years
Tab 1: Performance Comparison of HEU & LEU Cores
2.2 Neutron Activation Analysis
Unlike most reactors quantification by NAA with SLOWPOKE using the in-core irradiation sites does
not require co-irradiation of flux monitors or standards. The uniformity, stability and reproducibility of
the neutron spectrum within the core, and with time, facilitates the use of activation constants [3]
The irradiation, decay and counting schemes utilized in the acquisition of all data presented here are
shown in Table 2.
Schemes
Sample
mass(g)
Flux x Irradiation
10 11 ncm -2 s -1 time
First
Decay
First
count
Second
Decay
Second
count
Geological 0.20 2.5 2 10 min 5 min 60 min 10 min
Short
Geological 0.25 10.0 60 4-5 d 2 hr 21 d 5 hr
Long
Biological 0.7 5.0 3 3 min 5 min 40 min 10 min
short
Biological 1.0 10. 240 2-3(5*) d 3 hr 14 d 6 hr
long
*Human and animal tissue
Tab2: Optimized irradiation and measurement conditions
3. Results
All batches of samples irradiated during this work were irradiated along with Standard reference
materials (SRM) as part of the quality control, selected SRM’s wherever possible, were matrix match
to sample types. SRM’s were purchased either from NIST or IAEA and were generally within ± 20%
or better of certified values [4, 5, 6].
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