1. Isotopic and Nuclear Analytical Techniques for Health and Environment
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

2. Major pathways of radionuclides to man

3. Radionuclides of interest
- produced in fission processes which may contribute significantly to human exposure

4. Characteristics of strontium
90Sr (t1/2 = 28.7 y, Emax = MeV) 
90Y (t1/2 = 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

5. 90Sr 89Sr 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
89Sr

6. 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.

7. Samples selected milk powder, fruit milk mash,
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

8. Strontium separation procedure
preconcentration of alkaline elements
K and Si removal
separation of strontium and calcium
Ca removal
removal of Fe, Al

9. Strontium separation procedure – cont.
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

10. 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)

11. 90Sr activity calculation
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)

12. Results
TABLE I. RESULTS OF 90Sr DETERMINATION IN SELECTED FOOD AND FOODSTUFF SAMPLES,
Bq/kg FRESH WEIGHT

13. TABLE II. RESULTS FOR 90Sr IN FRESHWATER FISH SAMPLES, INCLUDED IN THE KRŠKO NPP MONITORING PROGRAMME

14. 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

15. 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