PHILOTECHNICS Decommissioning Radiological Laboratories in California CCRSO Conference October 5,...

PHILOTECHNICS

Decommissioning Radiological Laboratories in

California

CCRSO ConferenceOctober 5, 2007

Presented by:Jon Dillon, M.S.

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Decommissioning Planning

• Management commitment

• Key stakeholders

• Project team

• Establish reasonable timelines

• Development of RFP and project scope

• Early contact with CDPH

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Estimated Timelines

• Will vary depending on scope• Typical overall timeline

– Prepare Decommissioning Plan (15-30 days)– Submittal and approval to CDPH (~60 days)– Perform site survey (2-30 days)– Prepare Final Status Survey Report (15 days)– Submission and approval of report by CDPH

(Variable?)

• Terminating a facility typically takes from 3-6 months on average post FSS

• Make management aware early!!!

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Decommissioning Planning

• Perform Historical Site Assessment (HSA)– Review facility license and all amendments

– Employee interviews

– Monthly inventory logs

– Source leak test records

– History of releases or spills

• Performing a complete HSA is critical to maintaining the timeline and terminating the license

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Decommissioning Planning (cont.)

• Federal limit of 25 mrem/yr does not apply to CA • Currently no dose based release criteria in CA• Regulations specified in CCR Title 17, 30256• Case by case evaluation by CDPH• Select your facility's criteria

– ALARA– RAM License Conditions – Corporate Culture – Risk– Overall Timing for Decommissioning

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Decommissioning Criteria

• Contamination levels on building surfaces– Removable– Total

• Criteria Specified by – NRC Regulatory Guide 1.86– Facility RAM License Limits– NUREG-1757 – NUREG-1575 (MARSSIM )

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Regulatory Guide 1.86

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Facility RAM License Criteria

• Most conservative limits for Specific Licensees

• Not recommended– Increased radioactive wastes– Problematic for instrument detection limits– Usually only specifies a removable

contamination limit

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NUREG-1757

• Consolidated NMSS Decommissioning Guidance

• Three volumes addressing following topics:– “Decommissioning Process for Materials

Licensees”– “Characterization, Survey, and Determination

of Radiological Criteria”; and– “Financial Assurance, Recordkeeping, and

Timeliness”

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NUREG 1757 (cont.)

• Volume 2 of the NUREG provides guidance on compliance with radiological criteria for license termination

• Many sections of 1757 will reference to MARSSIM

• MARSSIM does not cover DCGL determination, subsurface contamination or materials and equipment, where 1757 does provide guidance

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NUREG-1575 (MARSSIM)

• Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM)

• Most up to date and statistically valid method for decommissioning

• Recognized by NRC, DOE, DOD, and EPA• Advantages

– True dose based assessment– Allows higher limits of contamination– Produces less radioactive wastes– Fewer sample locations required– Based on statistical certainties

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MARSSIM Process(Data Life Cycle)

• Plan (DQO Process)

• Implement (conduct surveys)– Scanning, direct measurements and sampling

• Assess (data quality assessment)– Statistical Tests and EMC

• Decide (compliance with release criteria)

• Evaluate (DQA)

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Example MARSSIM Based Criteria

• Derived Concentration Guideline Levels (DCGLs) Based on a 1 mrem/yr Dose Criteria

• Significant difference from historic guidelines

Isotope DCGLw’s

(DPM/100 cm2)

Removable DCGLw’s

(DPM/100 cm2)

H-3 5.0 x 106 1,000

C-14 1.5 x 105 1,000

P-32 3.8 x 105 1,000

P-33 1.7 x 106 1,000

S-35 5.0 x 105 1,000

I-125 2.7 x 104 1,000

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Determination of DCGL

• Outside scope of MARSSIM, however NUREG 1757 (NUREG-1727) provides guidance

• Consider scenarios– Residential, Commercial/Industrial, Recreational, etc.

• Consider pathways– External, Ingestion (water, meat, soils, etc.)– Drinking water– Inhalation

• DandD or RESRAD

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Types of DCGLs

• DCGLW

– DCGL for residual radioactivity evenly distributed over a large area

– Use with WRS or Sign test

• DCGLEMC

– DCGL for small areas of elevated activity

– Elevated measurement comparison to identify areas that require further investigation

– Different assumptions that DCGLW

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DQO Process

1. State the problem2. Identify the decision3. Identify inputs to the decision4. Define the study boundaries5. Develop a decision rule6. Specify limits on decision errors7. Optimize the survey design

DQO Process is a series of planning steps for establishing criteria for data quality and developing survey designs

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Example Data Quality Objectives (DQOs)

• Default Screening Values (DSVs)– Typically set at 20 to 50% of DCGLs

• Instrument Detection Limits (ideally)– Recommendation is the Static MDC is 10 – 50% of the

DCGL

• Must be known prior to selecting survey instrumentation

• Dose modeling analysis• Decision Errors

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Instrument Selection

• Research isotopes require sensitive instruments capable of detecting low energy beta emitters

• Separate instruments must be used to detect gamma emitters like I-125

• Instruments need to be calibrated at energies similar to isotopes of concern

• Calculate efficiencies correctly (2 vs. 4)

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Typical Instrument Specs

DetectorModel

Detector TypeDetector

AreaMeter Model

Window Thickness

Typical TotalEfficiency

Ludlum43-68

Gas FlowProportional

126 cm2 Ludlum 2350-10.4

mg/cm2 7% (14C)

Ludlum 43-37Floor Monitor

Gas FlowProportional

582 cm2 Ludlum 2350-10.8

mg/cm2 6% (14C)

EberlineSPA-3

2” x 2” NaI

20.4 cm2 Ludlum 2350-1 N/A900 cpm/R/hr

(137Cs)

BeckmanLS6000

Liquid Scintillation N/A Beckman N/A40% (3H)80% (14C)

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Typical Instrument MDCs

TypeDetectorModel

MeterModel

ScanRate

CountTime

Bkg(cpm)

MDC(dpm/100cm2)

SurfaceScans

Ludlum43-68

Ludlum2350-1

5cm/sec

N/A 458 2,594 (14C)

SurfaceScans

Ludlum 43-37

Ludlum2350-1

5cm/sec

N/A 1,480 959 (14C)

SurfaceScansSoils

EberlineSPA-3

Ludlum2350-1

0.5m/sec

NA 10,0002.03 pCi/g

(137Cs)

TotalSurfaceActivity

Ludlum 43-68

Ludlum2350-1

N/A 1 min. 458 1,163 (14C)

RemovableActivity

LiquidScintillation

Beckman N/A 1 min.8 (3H)

12 (14C)41 (3H)24 (14C)

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Typical Instruments

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MDC Comparison

• Large Area probe– ~6% total efficiency for C-14– Probe area 100 cm2

– Bkg ~350 cpm, 1 min counts

• G-M probe– ~3% total efficiency for C-14– Probe area 19.6 cm2

– Bkg ~50 cpm, 1 min counts

2

2 2

3 3.29 1( /100 )

. 100

b s b s b b

s b

R T T TMDC dpm cm

Eff T probearea cm cm

NUREG-1507

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MDC Comparison

• Large area probe– Static MDC is 1,500 dpm/100 cm2

– Scan MDC is 3,333 dpm/100 cm2

• G-M probe– Static MDC is 6,105 dpm/100 cm2

– Scan MDC is 18,179 dpm/100 cm2

• If you have restrictive DCGL you can see how instrument selection is critical

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Historical Site Assessment (HSA)

• Identify potential sources of contamination• Differentiate areas of different contamination

potential – Impacted vs. Non-Impacted• Provide input to scoping and characterization

survey design• Provide assessment for potential of contaminant

migration• Classification of Areas (Class 1, 2, 3)

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Characterization Surveys

• Biased based on history, material use and storage • Scan percentages based upon area classification• Be consistent with planned FSS to potentially use

as FSS data• Combination of scans, static and removable

measurements• Removable contamination measurements obtained

in areas of highest activity • Identifies areas of contamination which require

remediation

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Final Status Surveys

• Demonstrate that residual radioactivity in each survey unit satisfies release criteria

• Builds on data from HSA and results from scoping and/or characterization surveys

• Goal is to be able to reject null hypothesis meaning area meets release criteria

• Background reference areas very important• Sample size calculated that can statistically

demonstrate compliance with the derived concentration guideline levels (DCGLs)

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Does your lab look like this?

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Or this?

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Example Systematic Lab Design

11

1 2 3

456

7 8 9

12 10

2019

212223

18

242526

14 15 16 171327

28

29

30

31

32

33

34

3536

TYPICAL SPACING= 1.18m or 3' 10 14"

SYSTEMATIC SAMPLE LOCATION

RANDOM START

JUDGMENTAL SAMPLE LOCATION

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Typical FSS Report Contents

• Final Report will be prepared using the guidance of NUREG 1757 Volume 2, Section 4.5. The Final Report will include, at a minimum:

• An overview of the results of the FSS• A summary of the screening values (if used)• A discussion of any changes that were made in the FSS from

what were proposed in this plan• A description of the method by which the number of samples

was determined for each survey unit• A summary of the values used to determine the number of

samples and a justification for these values• A description of the data quality objectives used in the

design and performance of the Final Status Survey

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Typical FSS Report Contents (cont.)

• The survey results for each survey unit including the following:

• The number of samples taken for the survey unit;– A description of the survey unit, including (a) a map or drawing

showing the reference system and random start systematic sample locations for Class 1 and Class 2 survey units and reference area, as applicable, and the random locations shown for Class 3 survey units and reference areas; (b) discussion of remedial actions and unique features; and (c) areas scanned for Class 3 survey units and reference areas

– The measured sample concentrations in units comparable to the screening values

– The statistical evaluation of the measured concentrations

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Typical FSS Report Contents (cont.)

– Judgmental and miscellaneous sample data sets reported separately from those samples collected for performing the statistical calculations

– A discussion of anomalous data, including any areas of elevated activity detected during scan surveys that exceeded the investigation levels or any measurement locations in excess of the screening values

– A statement that a given survey unit satisfies the screening values and the elevated measurement comparison if any sample points exceeded the screening values

• A description of any changes in initial survey unit assumptions relative to the extent of residual activity (e.g., material not accounted for during site characterization)

• A description of how As Low As Reasonably Achievable practices were employed to achieve final activity levels.

• A final RESRAD or D&D run confirming dose

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FSS Key Considerations• Accurate HSA & consider decay when appropriate• Static MDC should be <50% of DCGL• Scan MDC comparison to DCGL for

determination of additional measurements• Proper classification of areas• Planning to minimize duplication• Equipment (Free Release)• Keep systems separate (e.g. vacuum, drain,

ventilation)• Licensing

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FSS Potential Pitfalls

• Poor instrument selection• Release limits not clearly defined• Scope of work not clearly defined• Selecting a DCGL that is too restrictive• MDCs of Instruments (Static, Scan)• Gross DCGL• Incorrect number of samples• Not addressing systems

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Summary

• Plan early & commit resources• Negotiations with CDPH• Internal staff vs. external support• FSS Report is key element for release• Time spent in planning and managing can reduce

overall timeline• Documentation, documentation, documenation• Success will be measured more by meeting

deadlines than meeting release limits

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Questions