1International Atomic Energy Agency, Division of Nuclear Power, Section of Nu-clear Power Technology Development, Vienna International Centre, PO Box 100 ...
Uranium Mining and Hydrogeology 2014 International Conference
UMH VII
Using High Temperature Reactors for Energy Neutral Phosphate Fertilizer and Phosphogypsum Processing Nils Haneklaus1, Harikrishnan Tulsidas2, Frederik Reitsma1 , Ewald Schnug3 1International Atomic
Energy Agency, Division of Nuclear Power, Section of Nu-clear Power Technology Development, Vienna International Centre, PO Box 100, 1400 Vienna, Austria 2International Atomic Energy Agency, Division of Nuclear Fuel Cycle and Waste Technology, Section of Nuclear Fuel Cycle and Materials, Vienna International Centre, PO Box 100, 1400 Vienna, Austria 3Technical University Braunschweig – Faculty 2 Life Sciences, Pockelsstraße 14, 38106 Braunschweig, Germany
INTRODUCTION
This work presents the conception to employ High Temperature Reactors (HTRs) to power a combined phosphate fertilizer/phosphogypsum (PG) processing plant that produces phosphate fertilizer by the wet acid process while treating the main associated byproduct PG to sulfuric acid/Portland cement. The idea is based on a past plant design proposed by Consolidated Minerals Inc. (CMI) from Florida and promotes the usage of a lean greenhouse gas emission energy source instead of the previously suggested coalfired plant.
Phosphate Rock
Reactor Core (Pebble Bed)
Fuel manufacturing from recovered uranium
Reactor Core (Block Type)
High Temperature Gas-cooled Reactor
Wet Acid Phosphate Rock Processing with Uranium Recovery
Phosphate Fertilizer
Side Reflector
Phosphogypsum Helium ≈ 250 ˚C
Sulfuric Acid
Process heat
Phosphogypsum Processing
Helium up to 1,000 ˚C
Energy Neutral Phosphate Fertilizer and Phosphogypsum Processing
I.
The possibility to realize temperatures as high as 1,000 ˚C makes HTGRs unlike the current LWRs and GCRs feasible for numerous high temperature (> 600 ˚C) heat applications beyond electricity production (e.g. steam generation, steam methane reforming, hydrogen production, desalination). Using HTGRs for nuclear heat applications makes power conversion obsolete and therefore leads to a higher efficiency factor of the entire plant. In addition to high temperature heat applications, considerably higher efficiency of electricity generation (HTGR 46 % with gas turbine, LWR 33 % with steam turbine) can be achieved.
Portland Cement
II.
HIGH TEMPERATURE GAS-COOLED REACTORS
The design of High Temperature Gas-cooled Reactors (HTGRs) a representative group of HTRs is different from present Light Water Reactors (LWRs) and Gas-cooled Reactors (GCRs) resulting in different possible applications. HTGRs such as the HTTR (High Temperature Engineering Test Reactor) in Japan are thermal reactors that use graphite as a moderator and helium as an inert coolant. The HTGR fuel consists of small coated particles that are about one millimeter in diameter. A few thousand of these fuel particles (e.g. PBMR 12,000) are compressed with graphite to (1) fuel compacts which are arranged in prismatic blocks forming a block type reactor core or (2) fuel pebbles resulting in a lose pebble bed reactor core. The figure above shows a simplified schematic cross section of an exemplary HTGR core. Relatively cold helium (approx. 250 ˚C) passes the core through the graphite side reflector entering it at the top. The helium flows through the core reaching a core outlet temperature of up to 1,000 ˚C. The core can either be a pebble bed (left side) or a block type (right side). For simplicity, both core types are shown together in the cross section. Heated helium leaving the core is cooled and purified from impurities such as graphite dust before being used again. The pictures below show past and present HTGR research- and prototype reactors as well as an extensive study that strongly influenced further HTGR developments carried out in South Africa. In addition to these reactors China is presently constructing a HTGR prototype reactor in Shandong Province.
DRAGON (1963-1976)
III.
ALTERNATIVE PROCESSING CHAIN
Extracting uranium from phosphoric acid during wet acid phosphate fertilizer processing is a well understood process that results in higher quality phosphate fertilizer products. The extracted natural uranium may be send to an established enrichment plant where it is further processed and later used to manufacture nuclear reactor fuel for the HTR employed. PG the main byproduct of wet acid phosphate fertilizer processing can in an energy intensive process be treated to sulfuric acid and Portland cement. As indicated in the figure above the sulfuric acid may again be used for wet acid phosphate rock processing, the Portland cement may be sold. CMI estimated that due to the integrated approach capital costs as high as 25 % of the estimated total capital costs of such a plant could be saved. Using a HTR instead of the previously proposed coal-fired plant might lead to fewer savings in capital costs but radically upgrades the greenhouse gas emissions of the whole plant. Present and upcoming efforts regarding “greener” production methods from regulation authorities may incentivize such combined plants. In total various environmental benefits such as a reduced environmental footprint, the chance to recover valuable resources from PG while solving a major disposal issue can be associated with a combined phosphate fertilizer/PG processing plant as it is described here. However, it is recognized that further investigations with view to the technical implementation and the economic feasibility are needed to evaluate the overall viability of the proposed conception.
PB-1
AVR
FSR
THTR
PBMR
HTTR
HTR-10
(1967-1974)
(1967-1988)
(1976-1989)
(1986-1989)
(1994-2009)
(since 1998)
(since 2000)
Source: http://www.iaea.org/NuclearPower/GCR/index.html
