Interesting findings of a comparison of Real Time versus Passive Radon Thoron Monitoring

In a Rare Earth MineMasood A InayatRSO, Molycorp Inc.July 14, 2015

Radon Thoron Monitoring

Objectives Impact of Passive monitoring in accurately

determining exposures Impact of single anomalous event on passive

monitoring Weighted averaging in real time versus linear

averaging in passive monitoring Radon Thoron ratio accuracy in real time monitoring

versus passive monitoring Timely results with ability to mitigate in real time

monitoring versus passive monitoring

Traditional approach passive monitoring Track Etch Detectors

Radon only

Type DNRM (Radon Only) Filter makes the short lived thoron (55

second half life) to decay before entering the detector

Radon plus thoron

Type DNRF (Radon + Thoron) No filter allows both radon & thoron to

enter the detector

Operation principle

Inside both Type DNRM & DNRF detectors is a piece of film that records the impacts (tracks) of alpha particles produced by the decay of radon/thoron and their decay by-products. These detectors are also knows as Alpha track or track etch detectors.

Continuous real time monitoring Alphaguard Continuous Real Time Radon Thoron monitor

Comparison Alpha Track (Passive) Alphaguard (Active)Low Per Unit Cost Yes NoAccuracy Somewhat YesReliability Somewhat YesTimeliness No Yes

Comparison

DNRF OR DNRM $15-$20 each X # of units deployed location X Monitoring Time frames (monthly quarterly etc.)2013 54 units monthly exchange 54 X 12 X15= $9720Currently 14 units quarterly exchange 14 X 4 X 20 = $1120

Alphaguard $12000-15000 per unit

Passive Vs. Real Time

A rare earth mine expansion perspective

Existing facilities for passive monitoring quarterly exchangeLegacy facilities monitored on quarterly exchange basis

CHP Fenceline Fenceline #1Fenceline #2 Fenceline #3

Didymium Packaging Lanthanum Packaging

2013 Existing Facilities Rn+Tn data comparison of real time versus passive monitoring shows consistent high results for real time monitoring as compared to passive monitoring

CHP Area Didy Room Fenceline #1 Fenceline #2 Fenceline #3 Lanthanum Packaging

0

1

2

3

4

5

6

7

8

2013 Real Time Vs Passive Exist-ing Facilities Comparison

Real Time Rn+Tn Passive Rn+Tn

CHP Area Didy Room Fenceline #1 Fenceline #2 Fenceline #3 Lanthanum Packaging

0

1

2

3

4

5

6

7

8

2013 Real Time Vs Passive Exist-ing Facilities Comparison

Real Time Rn+Tn Passive Rn+Tn

2013 Radon Only real time versus passive data shows relatively similar average radon concentrations although the difference is observed in different areas

CHP Area Didy Room Fenceline #1 Fenceline #2 Fenceline #3 Lanthanum Packaging

0

0.1

0.2

0.3

0.4

0.5

0.6

2013 Real Time Vs Passive Exist-ing Facilities Comparison

Real Time Rn Passive Rn

CHP Area Didy Room Fenceline #1

Fenceline #2

Fenceline #3

Lanthanum Packaging

0

0.1

0.2

0.3

0.4

0.5

0.6

2013 Real Time Vs Passive Ex-isting Facilities Comparison

Real Time Rn Passive Rn

2013 Thoron only real time versus passive data showing higher thoron concentrations for real time than passive monitoring.

CHP Area Didy Room Fenceline #1 Fenceline #2 Fenceline #3 Lanthanum Packaging

0

1

2

3

4

5

6

7

8

Real Time Tn Passive Tn

CHP Area Didy Room Fenceline #1 Fenceline #2 Fenceline #3 Lanthanum Packaging

0

1

2

3

4

5

6

7

8

Real Time Tn Passive Tn

New facilities online in 2013

With addition of new facilities beginning in 2013 a monthly radon thoron passive monitoring regime was put in place for the above listed facilities

New facilities for passive monitoring monthly exchangeNew facilities monitored on monthly exchange basis

PASTE TAIL OUTDOOR

PASTE TAIL DEPOSITORY

CRACK 1A LEVEL 3

CRUSHER

PASTE TAIL INDOOR NW FENCE LINE CRACK 1A LEVEL 1

NEW MILL

NE FENCE LINE SXH&I CHP INSIDE P16 FENCE LINESX-D MINE PIT CHP CERIUM CHLOR ALKALI

2013 average Radon + Thoron results are showing higher results throughout the year during the new facilities construction

Ce Se

p

Chor

Alkali

CHP

Crack

Crushe

r

Mine Pi

t

NE Fenc

e

New Mill

NW Fence

P-16 F

ence

Paste SX

DSX

H&I0

0.51

1.52

2.53

3.54

2013 Passive Radon + Thoron (DNRF) Yearly Weighted Average Monthly Exchange

2013 Passive Radon + Thoron (DNRF) Yearly Weighted Average Monthly Exchange

Passive Radon Thoron (DNRF) Monitoring Lo-cationsRa

don

Thor

on C

onc.

pCi

/litr

e

CERIU

M SEP

CHLO

R ALK

ALI

CHP

CRACK

Crushe

r

MINE PIT

NE Fen

ce Lin

e

NEW MILL

NW Fence

Line

P16 F

ENCE LINE

PAST

ESX

-DSX

H&I0

0.51

1.52

2.53

3.5Average Rn+Tn

Monitoring Locations

Rn +

Tn

Conc

. pCi

/lite

r

Note the average passive radon levels are consistently1pCi/liter or higher throughout 2013 as the construction of the new facilities was progressing

CERIU

M SEP

CHLO

R ALK

ALI

CHP

CRAC

K

Crushe

r

MINE PIT

NE Fen

ce Lin

e

NEW MILL

NW Fence

Line

P16 F

ENCE LI

NEPA

STE

SX-D

SXH&I

00.5

11.5

22.5

33.5

Average Radon Only

Monitoring Locations

Rn C

onc.

pCi

/lite

r

CERIU

M SEP

CHLO

R ALKAL

ICH

P

CRAC

K

Crushe

r

MINE PIT

NE Fen

ce Lin

e

NEW MILL

NW Fence

Line

P16 F

ENCE LI

NEPA

STE

SX-D

SXH&I

00.5

11.5

22.5

33.5

2013 Passive Radon (DNRM) Yearly Weighted Average Monthly Exchange

Average Radon Only

Note with the exception of crusher and mine pit Thoron levels are either low or non existent throughout new construction areas during 2013. Thoron levels in these two locations are somewhat higher as Radon levels

CERIUM SE

P

CHLO

R ALKAL

ICH

P

CRACK

Crushe

r

MINE PIT

NE Fenc

e Line

NEW MILL

NW Fence

Line

P16 FE

NCE LINE

PAST

ESX

-DSX

H&I00.5

11.5

22.5

33.5

2013 Passive Thoron (DNRF-DNRM) Yearly Weighted Average

Monthly ExchangeAverage Thoron Only

CERIU

M SEP

CHLO

R ALKA

LI CHP

CRAC

K

Crushe

r

MINE PIT

NE Fen

ce Lin

e

NEW MILL

NW Fenc

e Line

P16 F

ENCE LI

NEPA

STE

SX-D

SXH&I

00.5

11.5

22.5

33.5

Average Thoron Only

Monitoring Locations

Tn C

onc.

pCi

/lite

r

ConclusionsWhile new facilities were being constructed monthly exchange monitoring was carried out in 2013 to study the impact. The results painted an unexpected picture as inferred below:1)Average Radon concentration values in areas where ore

processing and beneficiation activities were not taking place were showing higher than normal radon levels

2)Areas where ore processing and beneficiation activities were taking place were showing almost similar results

3)Radon numbers were showing higher but thoron numbers did not go up higher relatively

4)There was a need to find a common source impacting radon levels site wide irrespective of ore processing and beneficiation activities

5)Was it a leak in the old P-16 tailings dam due to heavy earth moving and construction equipment moving activity

6)Was it related to dust control process 7)Any other potential cause?

All 7 Fenceline PASSIVE RADON (DNRM) locations are reported as “LESS THAN INDICATED VALUE”

2014 Real Time Vs. Passive Radon Comparison

Fencel

ine #1

Fencel

ine #2

Fencel

ine #3

CHP F

encel

ine

NW Fencel

ine

NE Fen

celine

P-16 F

encel

ine0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

2014 Real Time Vs. Passive Radon Comparison

2014 Real Time Rn 2014 Passive Rn

Fencel

ine #1

Fencel

ine #2

Fencel

ine #3

CHP F

encel

ine

NW Fencel

ine

NE Fen

celine

P-16 F

encel

ine0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

2014 Real Time Vs. Passive Radon Comparison

2014 Real Time Rn 2014 Passive Rn

2014 Passive fenceline monitors show a consistent “LESS THAN DETECTED VALUE” of 0.33pCi/liter of Radon concentration at all locations versus a variable and higher radon concentration for real time monitoring.

All 7 Fenceline PASSIVE THORON (DNRF - DNRM) locations are reported

Locations 2014 Passive Rn 2014 Passive Tn 2014 Passive Rn+TnFenceline #1 0.33 0.13 0.45Fenceline #2 0.33 0.53 0.85Fenceline #3 0.33 0.60 0.93CHP Fenceline 0.33 1.03 1.35NW Fenceline 0.33 0.35 0.68NE Fenceline 0.33 0.23 0.55P-16 Fenceline 0.33 1.10 1.43

Alphaguard 2014 Fencelines Real Time Radon Thoron Monitoring AveragesLocations 2014 Real Time Rn

2014 Real Time Tn 2014 Real Time Rn+Tn

Fenceline #1 0.54 0.48 1.02Fenceline #2 0.27 6.78 7.05Fenceline #3 0.56 2.48 3.04CHP Fenceline 0.45 1.33 1.78NW Fenceline 0.45 2.6 3.05NE Fenceline 0.4 1.22 1.62P-16 Fenceline 0.67 2.85 3.52

2014 Real Time Vs. Passive Thoron Comparison

Fencel

ine #1

Fencel

ine #2

Fencel

ine #3

CHP F

encel

ine

NW Fencel

ine

NE Fen

celine

P-16 F

encel

ine0

1

2

3

4

5

6

7

8

2014 Real Time Vs. Passive Thoron Comparison

2014 Real Time Tn 2014 Passive Tn

Fencel

ine #1

Fencel

ine #2

Fencel

ine #3

CHP F

encel

ine

NW Fencel

ine

NE Fen

celine

P-16 Fe

nceline

0

1

2

3

4

5

6

7

8

2014 Real Time Vs. Passive Thoron Comparison

2014 Real Time Tn 2014 Passive Tn

2014 Passive fenceline monitors show a consistent lower Thoron concentration at all locations versus a higher thoron concentration for real time monitoring.

All 7 Fenceline PASSIVE RADON + THORON (DNRF) locations are reported

2014 Real Time Vs. Passive Radon+Thoron Comparison

Fencel

ine #1

Fencel

ine #2

Fencel

ine #3

CHP F

encel

ine

NW Fencel

ine

NE Fen

celine

P-16 Fe

ncelin

e0

1

2

3

4

5

6

7

8

2014 Real Time Vs. Passive Radon+Thoron Comparison

2014 Real Time Rn+Tn 2014 Passive Rn+Tn

Fencel

ine #1

Fencel

ine #2

Fencel

ine #3

CHP F

encel

ine

NW Fencel

ine

NE Fen

celine

P-16 Fe

nceline

0

1

2

3

4

5

6

7

8

2014 Real Time Vs. Radon+Thoron Comparison

2014 Real Time Rn+Tn 2014 Passive Rn+Tn

2014 Passive fenceline monitors show a consistent lower Radon+Thoron concentration at all locations versus a higher radon+thoron concentration for real time monitoring.

DiscussionOre @Mountain Pass contains an average of 0.005% Uranium and 0.02% Thorium content therefore:1. Thorium content is almost 4 times higher than Uranium content2. Uranium is the parent for Ra-226 the precursor for Rn-2223. Thorium is parent for Ra-228 the precursor for Rn-220 4. Therefore the Rn-220 average concentration should be about a factor

of 4 higher than Rn-2225. Passive monitoring does not support this ratio whereas real time

monitoring does6. Passive monitoring shows lower exposures with radon thoron

combined than with radon alone7. Passive monitoring may report higher than actual exposure for Radon8. Passive monitoring may report lower than actual exposure for Thoron9. Significance of Radon is important but significance of Thoron cannot

be ignored either10.In case of passive monitoring once a high exposure event has been

recorded that affects the average for that time frame irrespective of the lows for that period

11.Real Time monitoring measures actual lows and highs of exposures and weighted averages are determined.

What Lies Ahead1)Passive monitoring has been in use and is

relied upon mostly due to its lesser cost2)Long term real time results need to be

acquired and data comparisons made3)Real time monitoring shows several

promising aspects such as immediate results, thereby helping provide opportunity to mitigate in a timely manner

4)Work areas where occupational workers are present should be relied upon with real time monitors as the circumstances and environment tends to change much more rapidly

5)Perimeters and fencelines can still me monitored using passive techniques as such areas are relatively less disturbed

Detailed Info

For more info on DNRM and DNRF monitors http://www.Landauer.com For more info on Alphaguard monitors http://www.saphymo.com

ContactMasood A InayatMolycorp Inc.,67750 Bailey RoadMountain Pass, CA 923661-760-856-7661 Direct1-702-280-6023 Cell1-760-856-5610 Faxhttp://www.Molycorp.comMasood.Inayat@Molycorp.com Email.