Gamma dose reduction for underground diamond drillers lawrence

Gamma Dose Reduction for Underground Diamond DrillersDr Cameron LawrenceSuperintendent Radiation & Occupational HygieneOlympic Dam

Radiation & Occupational Hygiene Department 2010 Slide 2

Disclaimer

Reliance on Third Party InformationThe views expressed here contain information that has been derived from publicly available sources that have not been independently verified. No representation or warranty is made as to the accuracy, completeness or reliability of the information. This presentation should not be relied upon as a recommendation or forecast by BHP Billiton. Forward Looking StatementsThis presentation includes forward-looking statements within the meaning of the U.S. Securities Litigation Reform Act of 1995 regarding future events and the future financial performance of BHP Billiton. These forward-looking statements are not guarantees or predictions of future performance, and involve known and unknown risks, uncertainties and other factors, many of which are beyond our control, and which may cause actual results to differ materially from those expressed in the statements contained in this presentation. For more detail on those risks, you should refer to the sections of our annual report on Form 20-F for the year ended 30 June 2009 entitled “Risk factors”, “Forward looking statements” and “Operating and financial review and prospects” filed with the U.S. Securities and Exchange Commission.No Offer of SecuritiesNothing in this release should be construed as either an offer to sell or a solicitation of an offer to buy or sell BHP Billiton securities in any jurisdiction.


Olympic Dam

• Large underground mining operation and processing plant for multi-mineral resource• Copper, Uranium, Gold & Silver

• Fourth largest copper mineral resource

• Fourth largest gold mineral resource• Largest uranium mineral resource


Underground Operations

• Over 300 km of developed underground tunnels• Workshops, offices, crib rooms and stores

• Mining occurs using open stopes• Ore removed from bottom of stopes and transported to ore handling system

• 2 underground ore handling systems including crushing and haulage• Whenan and Clark crushers and shafts


Radiation Monitoring Methods – Mine

• Radon Decay Products• Borak grab sampling method used• Monitoring program defines locations requiring sampling• Ventilation department perform pre entry and ongoing inspections,

data captured• Airway averages determined and doses calculated by linking to

timesheet location information• Radioactive Dust

• Minor pathway underground due to low ore grade, ~0.2 mSv/a• Workgroups sampled according to program using standard dust

monitoring equipment• Total alpha count and radioactive dust concentration determined• Workgroup averages calculated and doses applied depending on

timesheet information• Gamma

• All designated and selected non designated employees wear TLD badges attached to personal cap lamps

• Individual doses from TLD results, workgroup averages applied for missing badges

• Pre entry gamma surveys performed• Electronic monitoring programs in place using gamma watches and

dosicards


Average Mine Radiation Exposures FY09

• Exposure pathways• 57% from radon decay products• 38% from gamma radiation• 5% from dust

0

1

2

3

4

5

6

Backfi

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Corefar

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ent

Diamon

d Drill

ingElec

trician

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Fitters

Mine S

urfac

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Han

dling

Produc

tion C

hargi

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uctio

n Drill

ingRais

e Drill

ing

Service

s

Work Group

Dos

e (m

Sv)

Airborne Dust (mSv) Radon Decay Products (mSv) Gamma (mSv)


Diamond Drilling Operations

• Independent contractor operates 4 diamond drill rigs underground

• Diamond drilling program is used to determine ore resources and future stoping operations

• Drill rigs can be established at a site for up to 3 months

• Diamond drilling delivers core to the on site core processing facility for analysis preparation


Potential Gamma Exposures

• Site may be located in a mineralised area and have elevated gamma levels

• Localised mineralisation possible in walls, floor and/or roof

• Cuttings produced from drilling operations can give off high gamma levels

• >100 Sv/h historically recorded at some sites• Water seepage causing salt crystallisation

around drill holes can concentrate radionuclides

• Core handling activities• High grade core recorded at >100 Sv/h


Controls for Gamma Dose Reduction

• Diamond Drill Rig sites gamma surveyed prior to set up• In FY08 internal limits for the requirement of shotcrete at these sites was reduced from 8 Sv/h to 6 Sv/h

• In FY08 ground control methods at Olympic Dam were changed• This resulted in shotcrete being more widely used as a ground support tool


Controls for Gamma Dose Reduction

• Diamond Drill sites were being set up with more focus on good housekeeping

• Shotcrete, road base and drainage became common at all rig sites• Previously shotcrete was only used if gamma levels required it• Previously metal boxes around controls (TARDIS) were the only

engineering control for dose reduction• Some sites had poor drainage resulting in accumulation of cuttings around

drill rigs• Core storage segregation at rig sites


Site Setup


Site Setup

Drainage channel to remove cuttings

Metal control box to reduce exposure


Historical Average Exposures for Diamond Drillers

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

Jul04-Jun05 Jul05-Jun06 Jul06-Jun07 Jul07-Jun08 Jul08-Jun09

Period

Dos

e (m

Sv)

Dust RDP Gamma MAX Total Dose(mSv)


Average Gamma Exposures for Diamond Drillers

0.0

1.0

2.0

3.0

4.0

5.0

6.0

Jul04-Jun05 Jul05-Jun06 Jul06-Jun07 Jul07-Jun08 Jul08-Jun09

Year

Gam

ma

Dos

e (m

Sv)

Average Maximum

• Current rolling average for Diamond Drillers gamma exposure is 1.0 mSv (April 2009 – April 2010)


Conclusion

• Site decision to change ground control methods has reduced gamma exposures to all work groups

• Shotcrete readily applied throughout all areas of the underground operation• Focus on site set up for Diamond Drillers

• Use of concrete pads, metal boxes, shotcrete and drainage channels• Segregation of core

• Education about the importance of good housekeeping at rig sites• Drainage channels hosed out twice a shift

• Average gamma dose reduction of 43% for Diamond Drilling workgroup


Questions?

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Technology

Gamma dose reduction for underground diamond drillers lawrence