brazilian experience in remediation of norm sites
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BRAZILIAN EXPERIENCE IN REMEDIATION OF NORM SITES REMEDIATION OF - PowerPoint PPT Presentation

BRAZILIAN EXPERIENCE IN REMEDIATION OF NORM SITES REMEDIATION OF NORM SITES Dejanira da Costa Lauria Institute of Radiation Protection and Dosimetry Brazilian Nuclear Energy Commission (IRD/CNEN) Monazite Ce, La (PO 4 ) 39 % U 3 O 8


  1. BRAZILIAN EXPERIENCE IN REMEDIATION OF NORM SITES REMEDIATION OF NORM SITES Dejanira da Costa Lauria Institute of Radiation Protection and Dosimetry Brazilian Nuclear Energy Commission (IRD/CNEN)

  2. Monazite Ce, La (PO 4 ) ≈ 39 % U 3 O 8 ≈ 0,3 % ThO 2 ≈ 6 % � Monazite is basically an orthophosphate of Rare Earth Elements � Monazite is basically an orthophosphate of Rare Earth Elements containing thorium and uranium. � A typical Brazilian monazite contain around 0,3% of uranium oxide and 6% of thorium oxide. � Monazite is processed aiming obtaining lanthanide elements, but during the chemical processing wastes and residues are generated. � The chemical processing of monazite in Brazil stated in the forties years and the industry worked many years with out regulation concerning radiation protection.

  3. Basic Steps of the Monazite Chemical Processing MONAZITE 85-95 % pure Magnetic separation ������������ MONAZITE Light fraction Alkaline Digestion 99% Filtration Filtration Phosphate solution Hydroxide cake Th, U, Ra, REE Neutralization CAKE II Chloride solution Filtration ��������� Th and U hydroxide Ra and REE Precipitation REE chloride Mesothorium Cake ��������� Ba (Ra)SO4 ������������������������������������������������������������������������������ ���������������������������������� ���������������������!

  4. Legacy of the Monazite Processing � Disposal sites had to be set to storage the monazite's wastes and residues, which were disposed in shallow ground silos, in rubber drums or buried in trenches. 4 cps 0 cps 635 cps 533 cps 0 cps 5000 77 cps 321 cps 61 cps 236 cps 199 cps 65 cps 2137 cps 513 cps 0 cps 106 cps 73 cps 773 cps 3000 0 cps NA cps 3752 cps 3510 cps NA cps 3095 cps 45 cps 70 cps 0 cps 53 cps 745 cps 0 cps 20 cps 1000 126 cps 1551 cps 553 cps 0 cps 53 cps 20 cps 924 cps 106 cps 49 cps 191 cps ����#������� 300 �$%��"��� 449 cps 24 cps 122 cps NA cps 57 cps 0 cps 28 cps 24 cps 142 cps 0 cps 0 "���� �����������������������������������������

  5. &"'(�)*�'+$*, +�� ����-��� ��� ���� ���. ���� ���. /�� ����� /�� ����� �� �� "���� '���� ���� 0&"'(1 USAM ��� �2������� �� � �������� �� ���� ����� ��������! +�� (��� ��� �� ���� �� � ������. /�/������ ����������� ������ � �� "3� %���� ���.� ��� ������� ��. �� ���-��� �� ��/������ ���4�� � � ����!

  6. USAM Decomissioning The decommissioning was carried out in four steps: � the suitable packaging and the removal of wastes remaining 1. at the plant; the second stage was the decontamination and dismantling of 2. the equipment; the equipment; the third stage was the decontamination of floors and walls, 3. followed by the demolition of the buildings (built area of 13,000 m 2 ); and finally, the radiological survey of the site and its cleanup. 4.

  7. REMEDIATION ACTIONS 1) Site Radiological Characterization 1.a) Indentifing the main contaminants � Hystory of the site � Soil analyses by gamma spectrometry Soil analyses by gamma spectrometry 99,8 5 ����� ����� �� �� ��� ��� ����� ����� 6� 6�� �����6� ����6�� ����� ���� 5 99, ��� ��������� ��� ��������� ������������ ������������ ��������� ��������� 95, 90, ���� ���� ���������� ����������77 77 70, Fa (%) 50, 50, 5 56� 6�� �����6� ����6�� ����8��0��91�0 ���8��0��91�0����� ����� 1 1 30, 10, 56� 5 6�� �����6� ����6�� ����:4��0��91� ���:4��0��91� 5, 1, 0��;� 0 ��;� $$1 $$1 0,2 100 101 102 Ratio Ra-228/Ra-226

  8. REMEDIATION ACTIONS 1) Site Radiological Characterization 1.b) A survey of radionuclides in surface and deep soil was carried out . 5 6�������� ���"��<�.7� 5����7����#���� 5=����7�" ���������������� ��� 5)�2������.7�>%?��@��� ��� 5'�/�������2���������� �������

  9. 2.Establishment of the allowable residual level Inhalation Soil Ingestion External Radiation Based on: � � Dose limit of 1 mSv/y Worst case scenario: Child stays indoors for around 5500 h/y and in the � residential garden for about 700 h/y. The inhabitants did not consume water from the site, nor ingest any food grown on the site.

  10. Allowable residual level � The assessment was performed by pathway analysis (base of RESRAD): � External exposure was the main exposure pathway, being responsible for ca. 80-90% of the total dose. � The contribution of thorium-series radionuclides to the dose was � The contribution of thorium-series radionuclides to the dose was higher than the uranium-series one, and it increased with the increasing of the ratio Th/U. 228 Ra concentrations could be used as criteria for soil remediation. � 228 Ra � Considering the measured local background of soil concentration of 0.1 Bq/g, the allowable residual level ( ARL ) of 228 Ra was set to 0.65 Bq/g of soil.

  11. 3.Establishment of Methods for faster measurements ��� � ������������� �������� ����� tration of Ra-228 2,00 ��/��7 1,50 �1(����������������7�" ����������� (Bq/g) ������������ 1,00 (B Concentra 21�"�������/��������� 0,50 �����������������2������.�2.� 0,00 >%?� 0 200 400 600 Counting by second (cps) 6����������/�2������������ ����������������������������� ��� 6�� � ��<��.� �� ���������� 7 ��� 6��A����B�C��!���4�A /�B�� �!���� " �����������������������������������������7�+���<������������ /������ �����������<�������/���������<����������������0�!�4��������� ��� 6�1!�

  12. Establishment of Methods for faster measurements The gross alpha and beta � 1.2 counting showed a good 1 correlation with the activity a-228 (Bq/g) 0.8 228 Ra concentration of 0.6 (r total = 0.86, r beta = 0.93). Ra-2 0.4 0.4 Based on these results the Based on these results the � 0.2 gross beta counting was 0 chosen for the monitoring 0.00 1.00 2.00 3.00 4.00 5.00 during remediation. Beta total counting (Bq/g) Based on the original limit � established for the site, an allowable limit level of 3.5 Bq/g of gross beta counting in the soil at the site was derived

  13. 4.Protocol for soil Cleanup Radiological Survey Scintillator > 300 cps <300 cps Sampling of Soil Soil Removing > 30 Bq/g < 30 Bq/g Measurement Storage in Transfer to a USIN-a temporary by total beta counter Municipal landfill deposit > 3 Bq/g < 3 Bq/g Transfer to a CNEN Checking by municipal landfill Verificação final Regulatory Athority Ra-228 < 0.65 Bq/g Site releasing for unrestricted use

  14. USAM SITE "���������� ����������� ' ������ ������ D�<���������#/������� ������ �����������������

  15. Going on +��������/���������&"$,����������������������� �����/����� ����.�����������!

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