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