SEPARATION OF ACTINIDES AND LONG-LIVED FISSION PRODUCTS FROM HLW AT THE EUREX PLANT MTR FUEL REPROCESSING

Cel

THE PURPOSE OF THIS RESEARCH PROJECT IS TO SIMPLIFY THE PREDISPOSAL MANAGEMENT OF THE STORED LIQUID HLW AT THE EUREX PILOT PLANT. THIS WASTE CONSISTS OF THE AQUEOUS RAFFINATE OF THE FIRST EXTRACTION CYCLE (1AW) FROM THE REPROCESSING OF MTR-TYPE FUEL. THE 1AW-MTR LIQUID WASTE CONSISTS OF 85 M3 (STORED INTO STAINLESS STEEL TANKS) OF 1.1 M HNO3 SOLUTION WITH 27 G/L OF AL AND OTHER MINOR CONSTITUANTS, INCLUDING FISSION PRODUCTS AND REPROCESSING CHEMICALS.
THE DIRECT VITRIFICATION OF THIS WASTE WOULD REQUIRE A COMPLEX VITRIFICATION PLANT AND RESULT IN A LARGE AMOUNT OF VITRIFIED WASTE. THEREFORE THE OBJECTIVE IS TO SEPERATE THIS LIQUID WASTE INTO TWO PARTS: 1) A SMALL-VOLUME, HIGHLY RADIOACTIVE FRACTION, INCLUDING THE CS, SR AND ACTINIDES; 2) A LARGER-VOLUME, LOW LEVEL WASTE FRACTION CONTAINING THE MAJORITY OF THE INACTIVE SALTS PRESENT IN THE WASTE.
THE HIGH-LEVEL FRACTION MUST BE SUITABLE FOR VITRIFICATION, WITH THE OBJECTIVE OF IMMOBILISING THE WASTE IN THE SMALLEST POSSIBLE VOLUME OF GLASS. FROM PRELIMINARY STUDIES ON GLASS COMPOSITION /1/ THE ALUMINIUM AND THE SULFATE IN THE HIGH-LEVEL FRACTION SHOULD BE MINIMIZED (AL < 13 % W/W AS AL2O3).
THE LOW-LEVEL WASTE FRACTION MUST BE SUITABLE FOR CEMENTATION, AND IT SHOULD BE REDUCED TO THE SMALLEST PRACTICLE VOLUME. SCOPE OF RESEARCH WORK UNDER THIS CEC CONTRACT IS TO STUDY AND COMPARE THE PROPOSED CHEMICAL PROCESSES BY TECHNICAL AND ECONOMICAL CRITERIA.
The aim of this research was to separate selectively the actinides and long lived radioactive fission products from the bulk salt matrix of high level liquid waste (HLLW) coming from fuel reprocessing, which may contain up to 1.4 moles/litre of aluminium nitrate.
Studies included:
fission products and actinides selectively precipitated by using organic and inorganic reagents as sodium tetraphenylborate and phosphotungstic acid;
strontium and actinide coprecipitation by sorption on ferric hydroxide after solution alkalinisation;
ion exchange separation using polyantimonic acid and zeolites.
All the experiments were performed on a laboratory scale, using traced simulated solutions, and on real reprocessing waste in a hot cell.

In Italy there are some 120 m{3} of high level liquid waste (HLLW) coming from MTR, CANDU and Elk River fuel elements reprocessing. This HLLW contains a large amount of chemicals and inert salts (eg aluminium, mercury, iron, nitric acid) together with caesium, strontium and transuranic elements.

The possibility of separating radioactive isotopes from inert ones has been studied. Transuranic elements and strontium were separated by means of a selective precipitation, while caesium was adsorbed on synthetic zeolite (AZE process) or precipitated with sodium tributyl phosphate (ATE process). The decontamination factors for strontium, plutonium and caesium were respectively 100, 5000 and 1000. This selective separation allows the sophisticated and costly pot vitrification process to be used only for the small volume of high level waste while the larger volume of medium level waste is conditioned by the simpler process of cementation.
1. DEVELOPMENT OF CHEMICAL FLOWSHEETS, BY USING SIMULATED WASTE SOLUTIONS, FOR THE QUANTITATIVE SEPARATION OF CS, SR AND ACTINIDES FROM THE 1AW-MTR SOLUTION.
2. DEVELOPMENT OF SUITABLE SAMPLING EQUIPMENT FOR 1AW-MTR STORAGE TANK.
3. DESIGN AND REALIZATION OF A MINIPILOT PLANT TO TEST THE FLOWSHEETS WITH REAL 1AW-MTR FEED SOLUTION.
4. CHEMICAL AND RADIOCHEMICAL ANALYSIS OF REAL 1AW-MTR SOLUTION.
5. TESTS IN THE EQUIPPED HOT CELL WITH REAL 1AW-MTR SOLUTION.
6. GENERAL CONSIDERATIONS AND FINAL REPORT.

Dziedzina nauki

Program(-y)

FP1-RADWASTOM 3C - Research and development programme (Euratom) on the management and storage of radioactive waste, 1985-1989

Temat(-y)

Data not available

Zaproszenie do składania wniosków

Data not available

System finansowania

CSC - Cost-sharing contracts

Koordynator

Ente per le Nuove Tecnologie l'Energia e l'Ambiente (ENEA)

Wkład UE

Brak danych

Adres

Via Anguillarese 301
00060 Santa Maria di Galeria Roma
Włochy

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