Technologies and Experiences Technologies and Experiences of Decommission / Remediation of Decommission / Remediation

of China Uranium of China Uranium mining/milling facilitiesmining/milling facilities

Kick-off Meeting of the Network on Kick-off Meeting of the Network on Environmental Management and remediationEnvironmental Management and remediation

Lechang XuLechang XuBeijing Research Institute of Chemical EngineerinBeijing Research Institute of Chemical Engineerin

g and Metallurgy, CNNCg and Metallurgy, CNNC23 to Novenmber 2009, VIC, Vienna, Austria23 to Novenmber 2009, VIC, Vienna, Austria

中国核工业集团公司China National Nuclear Corporation

Beijing Research Institute of Chemical Engineering and Metallurgy

Scope of presentationScope of presentation

1 Environmental and Safe Issues from Uranium Ming/Milling

2 Decmmissioning / Remediation State and Technologies

3 Decommission / Remediation Experiences

4 Future Efforts

5 Recommended International Co-operation

中国核工业集团公司China National Nuclear Corporation

Beijing Research Institute of Chemical Engineering and Metallurgy

1 ENVIRNMENTAL AND SAFE ISSUES FROM URANIUM MINING/MILLING

中国核工业集团公司China National Nuclear Corporation

Beijing Research Institute of Chemical Engineering and Metallurgy

2 DECOMMISSION/REMEDIATION 2 DECOMMISSION/REMEDIATION STATE AND TECHOLOGIESSTATE AND TECHOLOGIES

Decommission and remediation of uranium mining/milling facilities includes :– underground mine sealing and plugging– open pit remediation– uranium milling tailings and waste rock

remediation– contaminated soil and water remediation– buildings (construct) and equipment and

material decontamination, etc.

中国核工业集团公司China National Nuclear Corporation

Beijing Research Institute of Chemical Engineering and Metallurgy

26 uranium production sites are closed out since 1990.

Up to now the decommissioning and remediation of 14 sites have been completed, of which 2 sites have been transferred to local government.

More than 9 Mt uranium debris and 1.75 Mt uranium tailings are remediated.

11.30Mt debris and 25Mt tailings are being remediated.

2 DECOMMISSION STATE 2 DECOMMISSION STATE AND TECHOLOGYAND TECHOLOGY

中国核工业集团公司China National Nuclear Corporation

Beijing Research Institute of Chemical Engineering and Metallurgy

2 DECOMMISSION STATE 2 DECOMMISSION STATE AND TECHOLOGYAND TECHOLOGY

Maximum individual effective dose reduce 70%~95% and less than 0.1mSv/a.

Radon flux and γ radiation level from tailings, mining debris and industry ground

surface radioactive level from buildings, construction and equipment and waste steel material

Radium content of land meet regulatory limit after remediation[1].

中国核工业集团公司China National Nuclear Corporation

Beijing Research Institute of Chemical Engineering and Metallurgy

2 DECOMMISSION STATE 2 DECOMMISSION STATE AND TECHOLOGYAND TECHOLOGY

Radioactive wastes have been effectively sealed upDecommissioned facilities stability improved Ecological environment rehabilitated after remediation Local government and public are pleased with the

remediation effects.

中国核工业集团公司China National Nuclear Corporation

Beijing Research Institute of Chemical Engineering and Metallurgy

2.1 Radon attenuation covering2.1 Radon attenuation covering

Covering material and covering framework natural and synthetic covering material

Natural: such as, clayed soil, sand soil, waste rock resulted from uranium production, industrial nonradioactive waste (titanium pigment waste solid, phosphorous tailings), lime

Synthetic : concrete, asphalt, textile fabric, geomembrane.

Natural material is preferred considering covering effect, covering cost and long term stability of cover.

中国核工业集团公司China National Nuclear Corporation

Beijing Research Institute of Chemical Engineering and Metallurgy

2.1 Radon attenuation covering2.1 Radon attenuation covering

Covering framework is sorted into single layer and multi-layer covering.

Covering thickness and effect are determined on the base of covering experiment

中国核工业集团公司China National Nuclear Corporation

Beijing Research Institute of Chemical Engineering and Metallurgy

2.1 Radon attenuation covering2.1 Radon attenuation covering

• Covering framework over uranium tailings pile of Lincang uranium mine is a typical multi-layer covering system [2]. From bottom to above – lime– Mining waste rock– Clayed soil– soil containing gravel– Revegetation

• Radon flux from tailings covered by mining waste rock reduced from original 10.64 to 2.8 Bq/m2.s.

中国核工业集团公司China National Nuclear Corporation

Beijing Research Institute of Chemical Engineering and Metallurgy

Equation (1) ~ (7) give the functions of radon flux as covering thickness on uranium milling tailings of Lincang uranium mine [1,2]: – Waste rock δ= -0.0269+1.796 ln(Fb/Fa) (1)– Clayed soil δ ＝ 1.218 ln(Fb/Fa) (2)– Sand soil δ=1.511 ln(Fb/Fa) (3)– Kaoline δ= -0.046+1.486 ln(Fb/Fa) (4)– 50# sand grout δ=0.0138+0.255 ln(Fb/Fa) (5)– 100# sand grout δ=0.02+0.112 ln(Fb/Fa) (6)– Kaoline grout δc =8.9×10-4+0.081 ln(Fb/Fa) (7)

Where, δ—covering thickness, m; Fb—radon flux before covering, Bq/m2.s; Fa—radon flux after covering, Bq/m2.s.

2.1 radon attenuation covering2.1 radon attenuation covering

中国核工业集团公司China National Nuclear Corporation

Beijing Research Institute of Chemical Engineering and Metallurgy

2.2 Mine tunnel close-out2.2 Mine tunnel close-out

Sealing and plugging of mine tunnel is optimal method to reduce mine discharge and radon release.

Flooding methods by combination of water-proof dam, grouting with heavy curtain and backfilling are researched. A water-tight patent material is developed.

中国核工业集团公司China National Nuclear Corporation

Beijing Research Institute of Chemical Engineering and Metallurgy

2.3 contaminated farmland and 2.3 contaminated farmland and soil remediationsoil remediation

Contaminated farmland and soil remediation– crop replanting,

• for example,rice repanted mulberry

– soil removal – soil replacement – plant remediation.

中国核工业集团公司China National Nuclear Corporation

Beijing Research Institute of Chemical Engineering and Metallurgy

2.4 surface decontamination2.4 surface decontamination

Surface decontamination [3]:scraping, strippable coating, chemical solvent

washing, re-meltingThe decontamination efficiency of various solv

ents is inorganic acid＞ organic acid＞ alkali and oxidant.

The best chemical decontamination solvent is 3%~5% sulfate acid, in which decontamination time is usually more than 1h but the better time is 3~4h；

中国核工业集团公司China National Nuclear Corporation

Beijing Research Institute of Chemical Engineering and Metallurgy

2.5 geological disaster prevention 2.5 geological disaster prevention and decommissioned facilities and decommissioned facilities

stabilizationstabilization

Waste rock pile stabilization Waste rock removalPlacing retaining wall. Water erosion preventionPackway and packway drain are built to reduce sl

ope height side slope is degraded as real side slope height

more than critical height

中国核工业集团公司China National Nuclear Corporation

Beijing Research Institute of Chemical Engineering and Metallurgy

2.5 geological disaster prevention 2.5 geological disaster prevention and decommissioned facilities and decommissioned facilities

stabilizationstabilization

Waste rock pile stabilization Side slope protection, such as,

Intercept water skeleton revetment rubble revetment grouting built revegetation combination of textile fabric and revegetation

intercept drain and discharge system

中国核工业集团公司China National Nuclear Corporation

Beijing Research Institute of Chemical Engineering and Metallurgy

2.5 geological disaster 2.5 geological disaster prevention and decommissioned prevention and decommissioned

facilities stabilizationfacilities stabilization

Wind erosion protection. RiprapBituminous mixture Changed nature clayed soil over radon

attenuation layer.

中国核工业集团公司China National Nuclear Corporation

Beijing Research Institute of Chemical Engineering and Metallurgy

2.5 geological disaster 2.5 geological disaster prevention and decommissioned prevention and decommissioned

facilities stabilizationfacilities stabilization Long term stabilization of uranium milling tailings

Dewatering of tailings, which is ultimate measure to reduce seepage from tailings pond contaminating surface water and groundwater, dam soakage and different settlement of covers;

Reinforcing tailings dam and embankment, including slope protection and degradation;

Constructing further diversion system, drainage channels, flood control structures, etc. if required.

Reshaping, degrading, covering and revegetating tailings pile to limit seepage, radon emission, surface gamma dose, and control erosion.

Collecting, treating and then discharging seepage from tailings pond;

Long term monitoring and maintenance

中国核工业集团公司China National Nuclear Corporation

Beijing Research Institute of Chemical Engineering and Metallurgy

3 DECOMMISSION / 3 DECOMMISSION / REMEDIATION EXPERIENCEREMEDIATION EXPERIENCE

The decommissioning technologies programme with “disposal on site, relative concentration, backfill and reclamation, mine tunnel sealing and plugging, reinforcement and stabilization, covering and revegetation, cleanup and decontamination” is explored

The principle with “specific site remediation, technology renovation, economic reasonable, safety feasible and environment protection, communication” must be insisted on.

中国核工业集团公司China National Nuclear Corporation

Beijing Research Institute of Chemical Engineering and Metallurgy

3 DECOMMISSION / 3 DECOMMISSION / REMEDIATION EXPERIENCEREMEDIATION EXPERIENCE

• Developing prophase studies to understand contaminated source term, contamination status and key safe and environmental issues

– environmental impact assessment– safety assessment – feasibility study

• Sorting priorities of decommissioning facilities and remediation sites on the base of environmental issues, decommissioning cost, technologies available and social factors

中国核工业集团公司China National Nuclear Corporation

Beijing Research Institute of Chemical Engineering and Metallurgy

3 DECOMMISSION / 3 DECOMMISSION / REMEDIATION EXPERIENCEREMEDIATION EXPERIENCE

• Emphasizing on solving physical construction safety issues, particularly ensuring safety stability of uranium tailings pond;

• Sealing and plugging mine tunnels as soon as possible to reduce contaminants release after closeout of underground mine.

中国核工业集团公司China National Nuclear Corporation

Beijing Research Institute of Chemical Engineering and Metallurgy

3 DECOMMISSION / 3 DECOMMISSION / REMEDIATION EXPERIENCEREMEDIATION EXPERIENCE

• Making the best of local resource and reduce second environmental impact. Such as,

– phosphate tailings is covered over uranium mining debris in Guizhou uranium mine;

– limekiln slag is backfilled into open mining pit in Xiushui uranium mine and

– mining debris is covered over uranium tailings of Lincang uranium mine;

• Opimizing decommissioning technology approachs;

中国核工业集团公司China National Nuclear Corporation

Beijing Research Institute of Chemical Engineering and Metallurgy

3 DECOMMISSION / 3 DECOMMISSION / REMEDIATION EXPERIENCEREMEDIATION EXPERIENCE

• Performing technical study of key environmental and safe issues. Such as

– radon attenuation covering of uranium tailings and mining debris;

– contaminated farmland and soil remediation; – safety analysis and assessment of uranium milling

tailings impoundment; – Radium transport of a radium mine; – sealing and flooding of underground mine; – contaminants transport modeling in groundwater; – passive treatment of seepage.

中国核工业集团公司China National Nuclear Corporation

Beijing Research Institute of Chemical Engineering and Metallurgy

3 DECOMMISSION / 3 DECOMMISSION / REMEDIATION EXPERIENCEREMEDIATION EXPERIENCE

• International exchange and co-operation, especially participating IAEA activities, Successively exchanges with Australia, Canada, Germany, France, Russia, Ukraine, and U.S. etc.

中国核工业集团公司China National Nuclear Corporation

Beijing Research Institute of Chemical Engineering and Metallurgy

4 4 FUTURE EFFORTS FUTURE EFFORTS

• Establish and revise decommissioning policy, code, regulation, standard, guideline, such as,– decommissioning / remediation implementation quality r

equirement– contamination investigation guideline– radon attenuation covering experiment provision, – decommissioning / remediation verification guide– long term monitoring and maintenance guidance of post-

decommission, etc.– Re-usage guidance of remediated sites

• Strengthen supervision and assessment on decommissioned facilities and remediated sites; 。

中国核工业集团公司China National Nuclear Corporation

Beijing Research Institute of Chemical Engineering and Metallurgy

4 4 FUTURE EFFORTS FUTURE EFFORTS

• Develop basis study on release, transport, transform of contaminants;

• Establish monitoring and assessment system and data-base of decommissioned facilities;

• Develop cost-effect technologies, emphasizing on contamination investigation and remediation of groundwater, overflowing water and soils, long-term stabilization of decommissioning facilities and rehabilization and reuse of remediated sites.

中国核工业集团公司China National Nuclear Corporation

Beijing Research Institute of Chemical Engineering and Metallurgy

5 RECOMMENDED 5 RECOMMENDED INTERNATIONAL CO-OPERATIONINTERNATIONAL CO-OPERATION

• Minimizing waste from uranium mining/milling facilities and their decommission;

• Passive water treatment technologies;

• Exchanging decommissioning /remediation strategies, regulation, standard and guide;

Thanks very muchThanks very much

中国核工业集团公司China National Nuclear Corporation

Beijing Research Institute of Chemical Engineering and Metallurgy

REFERRENCEREFERRENCE

• [1] Lechang Xu, Jianxin Xue and Shangxiong Gao. Several issues on the Decommissioning of Uranium Mining/Milling Facilities. Radiation protection (in Chinese), 2007, 27(2): 111-118.

• [2] Lechang Xu, Xingye Dai, Tianzheng Tang and Minghui Luo. Determing Radon Attenuation of Covers Using Field Experimentation. Uranium mining and metallurgy (in Chinese). 1993, 18(3): 179-186.

• [3] Lechang Xu and Yaohui Zhou. Surface Deontamination of Decommissioned Uranium mininng /Milling Facilities. GF report (in Chinese), 2005.