Transcript RADIONUKLIDI V IZBRANIH VZORCIH HRANE Urška Repinc

Isotopic and Nuclear Analytical Techniques for Health and Environment
10 - 13 June 2003, Vienna, Austria
90Sr
IN VARIOUS FOOD AND FOODSTUFFS
U. Repinc, L. Benedik, R. Jakopic
Department of Environmental Sciences
Jozef Stefan Institute, Jamova 39, 1000 Ljubljana, SLOVENIA
Major pathways of radionuclides to man
Radionuclides of interest
- produced in fission processes which may contribute significantly to
human exposure
Characteristics of strontium
90Sr
(t1/2 = 28.7 y, Emax = 0.546 MeV)

90Y (t
1/2 = 64.1h, Emax = 2.28 MeV)

90 Zr (stable)
89Sr
(t1/2 = 50.5 d, Emax = 1.49 MeV)

89Y (stable)
IIA. Group of the Periodic Table
-
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
90Sr
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
89Sr
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
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,
- meat (beef)
- freshwater fish: trout
- vegetables: cabbage, potato
mussels
Strontium separation procedure
sample ash + strontium carrier (100 mg Sr2+)
leaching with 50-100 mL conc.HCl
 filtrat ion
addition of o xalic acid
NaOH to pH 4-5
oxal ate preci pitation
discard solution
preconcentration of alkaline elements
K and Si removal
centrifugation 
dissolution in HNO3
fuming HNO3 separation (2 times or mo re)
nitrate preci pitation
discard solution
Ca removal
separation of strontium and calcium
centrifugation 
dissolution in deionized water
addition of Ba -carrier
addition of Fe-carrier
NH4 OH
hydroxi de preci pitation
discard precipitate
removal of Fe, Al
filtration  black belt filter paper
addition of Ba -carrier
addition of Fe-carrier
NH4 OH
Strontium separation
procedure – cont.
hydroxi de preci pitation
discard precipitate
filtration  black belt filter paper
addition of NH4 COOCH3
(NH4 )2 CrO4
CH3 COOH
chromate preci pitati on
discard precipitate
removal of Ba, Ra, Pb
filtration  black belt filter paper
addition of (NH4 )2 CO3
SrCO3 preci pitation
discard solution

beta mesurement of 90 Sr, 89 Sr and 90 Y
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
- 22 mm diameter planchettes
- calibrated with 90Sr/90Y standard
17% counting efficiency, 90Sr
43% counting efficiency, 90Y
A multilogger LB 5310 low-level gas
proportional counter
(Berthold Inc., Bad Wildbad, Germany)
90Sr
activity calculation
A - 90Sr activity in the sample, Bq/kg
Sr-90 - counting efficiency for 90Sr
R - count rate of the sample (without background), cpm
Y-90 – counting efficiency for 90Y
Rs+b -count rate of the sample and background, cpm
m - sample weight (kg)
Rb – background count rate, cpm
h – decay constant for 90Y (1.8022E-4 min-1)
ts – measuring time, sample
t – ingrowth time from separation of
counting (min)
tb – measuring time, background
YSr – chemical yield of the separation
90Sr
to
Results
TABLE 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
Conclusions
• 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