90 sr in various food and foodstuffs u. repinc, l. benedik, r. jakopic department of environmental...
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90Sr IN VARIOUS FOOD AND FOODSTUFFS
U. Repinc, L. Benedik, R. Jakopic
Department of Environmental Sciences
Jozef Stefan Institute, Jamova 39, 1000 Ljubljana, SLOVENIA
Isotopic and Nuclear Analytical Techniques for Health and Environment 10 - 13 June 2003, Vienna, Austria
Major pathways of radionuclides to man
Radionuclides of interest
- produced in fission processes which may contribute significantly to human exposure
Characteristics of strontium
89Sr (t1/2 = 50.5 d, Emax = 1.49 MeV) 89Y (stable)
IIA. Group of the Periodic Table
90Sr (t1/2 = 28.7 y, Emax = 0.546 MeV)
90Y (t1/2 = 64.1h, Emax = 2.28 MeV)
90 Zr (stable)
-chemically similar to calcium
-20-30% of absorbed Sr is deposited in the bone, 1% is distributed among the blood volume, extracellular fluid, soft tissue, and surface of the bone
-internal exposure to Sr-90 is linked to bone cancer, cancer of the soft tissue near the bone and leukemia
is considered one of the most hazardous fission products:
- high fission yield
- has a long physical half-life (28.7 years)
- has a long biological half-life (49.3 years)
- high radiotoxicity due to its tendency to deposit in bones
is one of the main component of fallout activity after an accident:
- high fission yield
- relatively short-lived (50.5 days), decays to undetectable levels in a few months
- it is not considered as hazardous as 90Sr
90Sr
89Sr
Food sampling
- individual food items, not total diet samples (to indicate which countermeasures should be taken to reduce population exposure)
- radionuclides most likely to be present in terrestrial food and environment
or can be rapidly accumulated by fresh water or marine organisms like oysters, clams, shrimp, etc.
Samples selected
- foodstuffs for infants
milk powder, fruit milk mash,
infant milk, wheat flakes
- eggs: whites and yolk
- sea food
golden grey mullet, gilthead seabream, European anchovy, mussels
- meat (beef)
- freshwater fish: trout
- vegetables: cabbage, potato
sample ash + strontium carrier (100 mg Sr2+)leaching with 50-100 mL conc.HCl
filtrat ionaddition of oxalic acid
NaOH to pH 4-5oxalate precipitation
dissolution in HNO3
fuming HNO3 separation (2 times or more)nitrate precipitation
dissolution in deionized water
addition of Ba-carrieraddition of Fe-carrier
NH4 OHhydroxide precipitation
addition of NH4COOCH3
(NH4)2CrO4
CH3 COOHchromate precipitation
addition of (NH4)2 CO3
SrCO3 precipitation
beta measurement of 90Sr, 89Sr and 90 Y
centrifugation
centrifugation
filtration black belt filter paper
filtration black belt filter paper
discard precipitate
discard precipitate
discard solution
discard solution
discard solution
sample ash + strontium carrier (100 mg Sr2+)leaching with 50-100 mL conc.HCl
filtrat ionaddition of oxalic acid
NaOH to pH 4-5oxalate precipitation
dissolution in HNO3
fuming HNO3 separation (2 times or more)nitrate precipitation
dissolution in deionized water
addition of Ba-carrieraddition of Fe-carrier
NH4 OHhydroxide precipitation
addition of NH4COOCH3
(NH4)2CrO4
CH3 COOHchromate precipitation
addition of (NH4)2 CO3
SrCO3 precipitation
beta measurement of 90Sr, 89Sr and 90 Y
centrifugation
centrifugation
filtration black belt filter paper
filtration black belt filter paper
discard precipitate
discard precipitate
discard solution
discard solution
discard solution
Strontium separation procedure
K and Si removalpreconcentration of alkaline elements
separation of strontium and calcium
removal of Fe, Al
Ca removal
Strontium separation procedure – cont.
sample ash + strontium carrier (100 mg Sr2+)leaching with 50-100 mL conc.HCl
filtrat ionaddition of oxalic acid
NaOH to pH 4-5oxalate precipitation
dissolution in HNO3
fuming HNO3 separation (2 times or more)nitrate precipitatation
dissolution in deionized water
addition of Ba-carrieraddition of Fe-carrier
NH4 OHhydroxide precipitation
addition of NH4COOCH3
(NH4)2CrO4
CH3 COOHchromate precipitation
addition of (NH4)2 CO3
SrCO3 precipitation
beta mesurement of 90Sr, 89Sr and 90 Y
centrifugation
centrifugation
filtration black belt filter paper
filtration black belt filter paper
discard precipitate
discard precipitate
discard solution
discard solution
discard solution
sample ash + strontium carrier (100 mg Sr2+)leaching with 50-100 mL conc.HCl
filtrat ionaddition of oxalic acid
NaOH to pH 4-5oxalate precipitation
dissolution in HNO3
fuming HNO3 separation (2 times or more)nitrate precipitatation
dissolution in deionized water
addition of Ba-carrieraddition of Fe-carrier
NH4 OHhydroxide precipitation
addition of NH4COOCH3
(NH4)2CrO4
CH3 COOHchromate precipitation
addition of (NH4)2 CO3
SrCO3 precipitation
beta mesurement of 90Sr, 89Sr and 90 Y
centrifugation
centrifugation
filtration black belt filter paper
filtration black belt filter paper
discard precipitate
discard precipitate
discard solution
discard solution
discard solution
removal of Ba, Ra, Pb
centrifugation on 22 mm diameter planchette, drying
determination of the chemical yield by weighing SrCO3
measurement of 89Sr, 90Sr/90Y on beta counter
Beta counting
A multilogger LB 5310 low-level gas proportional counter
(Berthold Inc., Bad Wildbad, Germany)
- 22 mm diameter planchettes - calibrated with 90Sr/90Y standard
17% counting efficiency, 90Sr 43% counting efficiency, 90Y
A - 90Sr activity in the sample, Bq/kg
R - count rate of the sample (without background), cpm
Rs+b -count rate of the sample and background, cpm
Rb – background count rate, cpm
ts – measuring time, sample
tb – measuring time, background
YSr – chemical yield of the separation
Sr-90 - counting efficiency for 90Sr
Y-90 – counting efficiency for 90Y
m - sample weight (kg)
h – decay constant for 90Y (1.8022E-4 min-1)
t – ingrowth time from separation of 90Sr to counting (min)
90Sr activity calculation
ResultsTABLE I. RESULTS OF 90Sr DETERMINATION IN SELECTED FOOD AND FOODSTUFF SAMPLES,
Bq/kg FRESH WEIGHT
TABLE II. RESULTS FOR 90Sr IN FRESHWATER FISH SAMPLES, INCLUDED IN THE KRŠKO NPP MONITORING PROGRAMME
TABLE III. RESULTS OF Sr-90 DETERMINATION IN SELECTED FOOD AND FOODSTUFF SAMPLES,
Bq/kg FRESH WEIGHT
TABLE IV. COUNCIL REGULATION (EURATOM) NO.3954/87 OF 22 DECEMBER 1987
• activity concentrations in selected food and foodstuff samples are low
(below detectable 0.01 to 0.9 Bq/kg 90Sr)
• activity concentrations in selected food and foodstuff samples are below maximum permitted levels of radioactive contamination laid down in EU regulations
• no significant differences in freshwater fish samples from the vicinity of
NPP Krško could be observed due to the operation of NPP
• results confirm that selected food and foodstuffs do not represent a health hazard to the population
Conclusions
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