A Methodology for Post Operational Clean Out of a Highly Active Facility Including Solids Behaviour - 12386
- National Nuclear Laboratory, Sellafield, Seascale, Cumbria, CA20 1PG (United Kingdom)
- Sellafield Limited, Sellafield, Seascale, Cumbria, CA20 1PG (United Kingdom)
The Highly Active Liquor Evaporation and Storage (HALES) plant at Sellafield handles acidic fission product containing liquor with typical activities of the order of 18x10{sup 9} Bq/ml. A strategy experimental feedback approach has been used to establish a wash regime for the Post Operational Clean Out (POCO) of the oldest storage tanks for this liquor. Two different wash reagents have been identified as being potentially suitable for removal of acid insoluble fission product precipitates. Ammonium carbamate and sodium carbonate yield similar products during the proposed wash cycle. The proposed wash reagents provide dissolution of caesium phosphomolybdate (CPM) and zirconium molybdate (ZM) solid phases but yields a fine, mobile precipitate of metal carbonates from the Highly Active Liquor (HAL) supernate. Addition of nitric acid to the wash effluent can cause CPM to precipitate where there is sufficient caesium and phosphorous available. Where they are not present (from ZM dissolution) the nitric acid addition initially produces a nitrate precipitate which then re-dissolves, along with the metal carbonates, to give a solid-free solution. The different behaviour of the two solids during the wash cycle has led to the proposal for an amended flowsheet. Additional studies on the potential to change the morphology of crystallising ZM have presented opportunities for changing the rheology of ZM sediments through doping with tellurium or particular organic acids. Two different wash reagents have been identified as being potentially suitable for the POCO of HALES Oldside HASTs. AC and SC both yield similar products during the proposed wash cycle. However, the different behaviour of the two principle HAL solids, CPM and ZM, during the wash cycle has led to the proposal for an amended flowsheet. Additional studies on the potential to change the morphology of crystallising ZM have presented opportunities for changing its rheology through doping with tellurium or certain organic acids. A strategy-experimental feedback approach has been used to establish a wash regime for the POCO of the HALES facility at Sellafield. The close working of the strategy and experimental teams has permitted a wash sequence to be developed which is considered to be robust by both sides. The technical underpinning of the strategy is expected to make stakeholder buy-in more readily achievable. (authors)
- Research Organization:
- WM Symposia, 1628 E. Southern Avenue, Suite 9-332, Tempe, AZ 85282 (United States)
- OSTI ID:
- 22293632
- Report Number(s):
- INIS-US-14-WM-12386; TRN: US14V1288115156
- Resource Relation:
- Conference: WM2012: Waste Management 2012 conference on improving the future in waste management, Phoenix, AZ (United States), 26 Feb - 1 Mar 2012; Other Information: Country of input: France; 6 refs.
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CESIUM
DISSOLUTION
EVAPORATION
FISSION PRODUCTS
MOLYBDATES
NITRIC ACID
ORGANIC ACIDS
PRECIPITATION
REAGENTS
REMOVAL
SEDIMENTS
SODIUM CARBONATES
SOLIDS
STORAGE
TELLURIUM
ZIRCONIUM