200420042004 11
Determination of thermal neutrons with LiF TLD
Determination of thermal Determination of thermal neutrons withneutrons with LiFLiF TLDTLD
ZeevZeev B.B. AlfassiAlfassiDepartment of Nuclear Department of Nuclear
engineeringengineering
200420042004 22
200420042004 33
200420042004 44
200420042004 55
200420042004 66
200420042004 77
200420042004 88
200420042004 99
200420042004 1010
200420042004 1111
200420042004 1212
200420042004 1313
200420042004 1414
200420042004 1515
200420042004 1616
TTPstandard
long TTP for γirradiationlong TTP for thermal
neutrons irradiation
200420042004 1717
0
1270
18-
ROI-67ROI-45
200420042004 1818
irradiation γ ROI(4+5) irradiationirradiation γγ ROI(4+5)ROI(4+5)
y = 0.3548x + 0.0502R2 = 0.9999
0
5
10
15
20
25
0 10 20 30 40 50 60
Dose (mSv)
RO
I 45
(mill
ions
of c
ount
s)
200420042004 1919
irradiation γ ROI(6+7) irradiationirradiation γγ ROI(6+7)ROI(6+7)
y = 6.5176x + 4.3933R2 = 0.9998
050
100150200250300350400
0 10 20 30 40 50 60
Dose (mSv)
RO
I 67
(thou
sand
s of
cou
nts)
200420042004 2020
200420042004 2121
200420042004 2222
Dose ROI-45 stdv (%) of ROI-67 stdv (%) of Normalized area/mSv***
(mSv) (*) ROI-45 (**) ROI-67 ROI-45 ROI-67
3 1.09 6.50 23.46 18.84 1.00 ± 0.07 1.00 ± 0.19 6 2.21 11.04 44.50 17.80 1.01 ± 0.11 0.95 ± 0.17 9 3.32 8.18 64.85 12.70 1.01 ± 0.08 0.92 ± 0.12 12 4.27 8.88 82.07 12.52 0.97 ± 0.09 0.87 ± 0.11 25 8.84 8.89 164.35 11.63 0.97 ± 0.09 0.84 ± 0.09 50 17.82 7.94 331.48 9.76 0.98 ± 0.08 0.85 ± 0.08
Table 1. The areas of the regions of interest of peaks 4+5 and 6+7 for different gamma ray doses from a 137Cs source.
(*) ROI-45 is the glow curve area in the region of peaks 4 and 5 in millions of counts. (**) ROI-67 is the glow curve area in the region of peaks 6 and 7 in thousands of counts. (***) Normalization of the area/mSv value to the value at 3mSv.
200420042004 2323
6+4/7+5 66++44//77++55
Gamma rays
0,01
0,015
0,02
0,025
0,03
0 10 20 30 40 50 60Dose (mSv)
Rat
io o
f pea
ks 6
&7 /
4&5
200420042004 2424
6+4/7+5 66++44//77++55
Thermal neutrons
0,1
0,15
0,2
0,25
0,3
0 2 4 6 8 10Irradiation time (hours)
Rat
io o
f pea
ks 6
&7 /
4&5
200420042004 2525
200420042004 2626
200420042004 2727
0.1 1 100.00
0.05
0.10
0.15
0.20
0.25
Chi^2 = 3.3857E-6R^2 = 0.99927 P1 0.018 ± 0.00061P2 0.21533 ± 0.00106
A 67 /
A45
Dn / Dγγγγ
200420042004 2828
0
2
4
6
8
10
12
25 50 75 100 125 150 200
Channel
Arb
itrary
scale
Normalized PTTL glow curves from TLD-600 . following neutron irradiation.
- - - - - - following gamma ray irradiation.
200420042004 2929
y = 0.1663x + 0.6767R2 = 0.9962
y = 0.1549x + 0.4556R2 = 0.9968
y = 0.0718x + 0.2424R2 = 0.9966
y = 0.0714x + 0.251R2 = 0.9972
0
2
4
6
8
10
12
14
16
18
20
0 20 40 60 80 100 120 140
Original readout
PTTL
G3_TTP5G4_TTP5G3_TTP2G4_TTP2
PTTL vs. the original readout for thermal neutrons (mGy - 137Cs equivalent),for two readout times: - TTP2 : 20 seconds readout - TTP5 : 13.3 seconds readout.
200420042004 3030
Gamma ray exposure Neutron exposure Exposure (mSv) % PTTL Exposure (mSv) % PTTL
5 8.6 ± 1.0 1.5 36 ± 4 10 7.3 ± 0.9 2.5 30 ± 3 15 7.0 ± 0.8 4.2 29 ± 2
5.8 28 ± 1 7.7 31 ± 3
AVERAGE : Pg = 7.6 ± 1 % AVERAGE : Pn = 31 ± 3 %
200420042004 3131
DTOT = DG + DN PTOT = (PG*DG + PN*DN ) / 100
DTOT - The total dose in a mixed field. DG - The gamma dose contribution. DN - The neutron dose contribution. PTOT - The total PTTL reading. PG - PTTL percent for gamma rays (7.6%). PN - PTTL percent for neutrons (31%).
100( ) /100
NTOT TOT
GN G
PD PD
P P
−=
−100
( ) /100
GTOT TOT
NN G
PP DD
P P
−=
−
200420042004 3232
200420042004 3333
200420042004 3434
200420042004 3535
200420042004 3636
200420042004 3737
200420042004 3838
200420042004 3939
200420042004 4040
200420042004 4141
200420042004 4242
200420042004 4343
200420042004 4444
200420042004 4545
200420042004 4646
200420042004 4747
200420042004 4848
200420042004 4949
200420042004 5050
200420042004 5151
200420042004 5252
200420042004 5353
