Download No Slide Title

FT 5.12 Determination of the radiation hazards due to
tritiated dusts and flakes at JET)
Part 1 - Literature review - (L Di Pace, ENEA)
Part 2 - Experimental determinations (B Patel, UKAEA)
UKAEA
November 2005
FT 5.12: Experimental determination of the radiation
hazards due to tritiated dusts and flakes at JET
Part 2 - Experimental determinations (UKAEA)
Current status
A large part of the experimental work as originally envisaged
is complete, but some still on-going.(Work being done by
NRPB(HPA) and Lovelace Respiratory Research Institute)
Samples: Dust from surface layers of MKIIa tile, 2004
poloidal limiter tile, 2004 vacuum cleaner dust, single paper
air-samples, multi-stage cascade air samples
FT 5.12: Experimental determination of the radiation
hazards due to tritiated dusts and flakes at JET
Complete, results received: Size analysis, Specific Surface
area, SEM (Lovelace)
Complete, awaiting final results: Dissolution (NRPB(HPA))
Repeat analysis: Tritium content (Lovelace)
FT 5.12: Experimental determination of the radiation
hazards due to tritiated dusts and flakes at JET
Repeat analysis: Tritium content (Lovelace)
- Original acid dissolution method very slow
- Provided CEA paper on wet-ashing using perchloric acid
- Insufficient detail to replicate in lab
- Contractual problems, now pursuing an oxidation method
- Further time needed to complete this part of the work and
check influence on other factors
FT 5.12: Experimental determination of the radiation
hazards due to tritiated dusts and flakes at JET
For tritium content, also approached:
- Tritium Laboratory Karlsruhe for calorimetry*
- JET AGHS for calorimetry*
- CEA for wet ashing#
*vacuum cleaner dust
#tile dust
FT 5.12: Experimental determination of the radiation
hazards due to tritiated dusts and flakes at JET
NEW Results of In-Vessel Air Sampling in 2004 SD
a) Seven single cyclopore paper samples
b) Twenty (9-stage) impactor samples
Covered wide range of remote and manual operations in
2004 shutdown
FT 5.12: Experimental determination of the radiation
hazards due to tritiated dusts and flakes at JET
Twenty (9-stage) impactor samples were taken - cut points
from 21um to 0.5um - allows measurement of AMAD,
mostly analysed at JET by Liquid Scintillation Counting
Scenario 1 (early stage after intake, partial availability of
tritium) - all samples counted by LSC
Scenario 2 (late stage after intake, full availability of tritium)
- 2 samples counted following oxidation technique
FT 5.12: Experimental determination of the radiation
hazards due to tritiated dusts and flakes at JET
(Scenario 1, LSC count)
Sample # 17, fitted line, AMAD = 11.4um gsd=2.4, manual
welding
sample 17 on 24.08.04
Percent of activity less than Dp
100.0
10.0
1.0
0.1
0.1
1
Cut point (mm)
10
100
FT 5.12: Experimental determination of the radiation
hazards due to tritiated dusts and flakes at JET
(Scenario 1 (LSC count))
Sample # 3, fitted line, AMAD = 3um, gsd = 3.6, Remote
work
sample 3 on 20.05.04
Percent of activity less than Dp
100.0
10.0
1.0
0.1
0.1
1
Cut point (mm)
10
100
FT 5.12: Experimental determination of the radiation
hazards due to tritiated dusts and flakes at JET
Scenario 1 and 2 - comparison of LSC counting (4.19um) to
full oxidation (7.98um)
Sample 14 : AEAT oxidation results
Sample 14 : On-site LSC results
100.0
Percent of activity less than
Dp
Percent of activity less than
Dp
100.0
10.0
1.0
0.1
0.1
1
Cut point (mm)
10
100
10.0
1.0
0.1
0.1
1
Cut point (mm)
10
100
FT 5.12: Experimental determination of the radiation
hazards due to tritiated dusts and flakes at JET
The ratio of the activity values by LSC counting and
oxidation
Sample 14 : Ratio (LSC/oxidiser) vs. particle size
1.200
Ratio (LSC/oxidiser)
1.000
0.800
0.600
0.400
0.200
0.000
0.1
1
10
Particle size (um )
100
FT 5.12: Experimental determination of the radiation
hazards due to tritiated dusts and flakes at JET
Findings on the in-vessel air sampling:
a) Surface bound tritium - AMAD values range from 3um to
11um
b) Some correspondence to nature of work, but not always
c) Actual sample activities are mostly non-linear and bi- or
multi-modal
d) Detailed analysis needed to unfold and calculate %
contributions to multiple AMADs
e) Can experimentally see a self-absorption effect with
particle size
FT 5.12: Experimental determination of the radiation
hazards due to tritiated dusts and flakes at JET
Findings on the in-vessel air sampling:
f) - Allows results by LSC only to be extrapolated to total
tritium if needed for remaining samples
g) - The availability of tritium to body fluids is a function of
desorption characteristics. Using this data, the dose
calculation can be applied according to early or late stage
after intake. AMAD values will vary for surface bound
tritium only and full volume bound, and consequently the
dose