Release of Material from Radiological Controls in

Accelerators

Sayed Rokni, Jim Allan, Alberto Fasso, James Liu, Amanda Sabourov, Joachim Vollaire, and Hirokuni Yamanishi

Radiation Protection DepartmentSLAC National Accelerator Laboratory, U.S.A.

DOE Accelerator Safety Workshop, SLAC, August 17-19, 2010,

Release of Material from Radiological Controls in

Accelerators

Sayed Rokni, Jim Allan, Alberto Fasso, James Liu, Amanda Sabourov, Joachim Vollaire, and Hirokuni Yamanishi

Radiation Protection DepartmentSLAC National Accelerator Laboratory, U.S.A.

DOE Accelerator Safety Workshop, SLAC, August 17-19, 2010,

• Regulatory Background• Secretarial Memoranda• Site Impact

– PEP-II, BaBar• Induced Radioactivity in Accelerators

– Activation characteristics– Surface measurements– Proxy radionuclides

• Radiological Clearance Workshop– Volumetric release criteria – Measurement protocols

• Expected Outcomes from the Workshop

2

OutlineOutline

Regulatory BackgroundRegulatory Background

• DOE Order 5400.5-1993 has provided requirements and guidelines for unrestricted release of property from radiological control

• Specific limits for surface contamination levels are prescribed in the

Order

• No limits are given for release of material that has volumetric radioactivity. Such volumetrically contaminated materials may be released only on a case-by-case basis if criteria and survey techniques are approved by DOE

• For use with DOE Order 5400.5, DOE issued a draft Guide G 441.1-xx in 2002 for the implementation of the control and release of property that may contain residual radioactive material

3

Secretarial MemorandaSecretarial Memoranda

• Secretarial Moratorium (January 2000)– Prohibits the release of volumetrically contaminated

metals … into commerce

• Secretarial Suspension (July 2000, modified January 2001) – Suspends the unrestricted release for recycling of

scrap metals from radiation areas within DOE facilities– Radioactive or not

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5

PEP-II B Factory at SLACPEP-II B Factory at SLAC

* Radioactive components (< 6%)

HER = 2200 m, LER = 2200 mHER injection line = 2300 m, LER injection line = 2900 mTotal length of beam line = 9600 m (6.0 miles)

6

Preliminary Field Surveys: PEP ActivationPreliminary Field Surveys: PEP Activation

• Gross survey map• Yellow shading

represents some items in the area read above background – used Ludlum Model-18

with 44-2 1”x1” NaI detector

7

Structures from BaBar DetectorStructures from BaBar Detector

Magnet flux return (slabs of steel) and support girders

CERN LEP and DetectorsCERN LEP and Detectors8

9

SLAC Site ImpactSLAC Site Impact

 Volume

(ft3)Area (ft2)

Landfill burial Shipping Cost Labor Cost

PEP-II 104106 33021 $1,041,058 $2,002,035 $1,500,000

BABAR 15625 5600 $289,250 $339,523 $500,000

Property Control (Hold) 104167 32541 $1,041,670 $2,713,269 $1,975,000

SUBTOTALS     $2,371,978 $5,054,827 $3,975,000

           

TOTAL         $11,401,805

Induced Radioactivity in AcceleratorsInduced Radioactivity in Accelerators

-Induced radioactivity is volumetric with maximum at a surface

-Profile of radionuclides

10

Electron Beam Loss

Potential Activation in Electron Accelerators Tunnel

High-Energy and Low-Energy Neutrons

Bremsstrahlung Photons

11

• Photonuclear• Spallation • Neutron

Capture

11

Beam LossesBeam Losses

• Beam losses, and consequent material activation, occur only on limited portions of an accelerator facility

• Some are produced on a small number of components designed to intercept the full beam power(targets, beam dumps) or a fraction of the beam (collimators)

• Other abnormal losses may occur at a few locations, due to mis-steering

• Most components (magnets, support structures, sections of vacuum chamber) do not become radioactive, especially at electron accelerators

12

Activation Characteristics Activation Characteristics

• No alpha emitters are produced• No surface contamination in metals and other solid

materials due to beam operations• For material release purposes, in general, most abundant

radioisotopes are those with a half-life of the order of the irradiation time (about 1 to 10 years)

• Induced activity in an object is volumetric and presents its maximum at the surface that faces beam loss points – This supports surface measurements

• Radioisotopes that are difficult to detect are generally accompanied by “proxy” radioisotopes that can be clearly measured– This supports measurements for proxy radioisotopes, instead of measurements for

all potential radioisotopes that can be produced

13

Critical and Proxy RadioisotopesCritical and Proxy Radioisotopes

Material Radionuclide Half-life

Carbon steel (Fe, C)andCast iron (Fe, C, Si, Mn)

22Na (proxy) 2.6 y54Mn (proxy) 312 d55Fe (5.9 keV x-ray) 2.73 y57Co 272 d

Aluminum 22Na 2.6 y

Copper 55Fe (5.9 keV x-ray) 2.73 y57Co 272 d60Co (proxy) 2.6 y

Concrete 3H (pure beta) 12.3 y22Na (proxy) 2.6 y

54Mn (proxy) 312 d55Fe (5.9 keV x-ray) 2.73 y57Co 272 d60Co 5.26 y152Eu, 154Eu 13.5 y, 8.59 y

Proxy radioisotopes (22Na,

54Mn, 60Co) emit high-energy and high-intensity gamma rays

10 Sv/y ANSI N13.12Screening Level (SL):22Na, 54Mn, 60Co: 30 pCi/g55Fe, 3H: 3000 pCi/g

Detection Limit requirement:∑i (MDAi / SLi) 1

Radioisotopes with long half-lives are of interest.

Hard-to-measure radioisotopes (3H, 55Fe) emit only beta or low-energy X rays

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Example of FLUKA Induced Activity Calculations: BaBar Detector at SLACExample of FLUKA Induced Activity Calculations: BaBar Detector at SLAC

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Three Floors High,

Thousands of Pieces

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Volumetric Activation Profile in MetalsVolumetric Activation Profile in Metals

The activity profile of each BaBar component has its maximum on the side that faces the source (e+ and e- collision point)

SLAC Radiation Protection Dept. Note 09-04, 2009

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Example of FLUKA benchmark – Exp T489 at SLACExample of FLUKA benchmark – Exp T489 at SLAC

• Copper sample down beam of the target

Comparison of the calculated and measured residual activity

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Radioisotopes for Metals in BaBarRadioisotopes for Metals in BaBar

Radioisotope Half-lifeFLUKA-Calculated Specific Activity in pCi/g (% of total)

1 year 2 years 5 years

60Co (proxy) 5.3 y 1.0×10-6 (22%) 8.9×10-7 (27%) 6.0×10-7 (38%)

57Co 272 d 9.4×10-8 (2%) 3.7×10-8 (1.1%) 2.3×10-9 (0.1%)

55Fe 2.7 y 2.4×10-6 (53%) 1.9×10-6 (57%) 8.8×10-7 (55%)

54Mn (proxy) 313 d 6.5×10-7 (14%) 2.9×10-7 (9%) 2.5×10-8 (1.6%)

49V 338 d 2.7×10-7 (6%) 1.3×10-7 (4%) 1.4×10-8 (0.9%)

3H 12.3 y 6.9×10-8 (1.5%) 6.5×10-8 (2%) 5.5×10-8 (3.4%)

Remaining — 2.3×10-8 (0.5%) 1.0×10-8 (0.3%) 6.1×10-9 (0.4%)

Radioactivity in the BaBar IFR forward steel plug at three decay times

(SA/SL) for 55Fe is much less than (SA/SL) for 60Co

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FLUKA-calculated Activity Profiles in Concrete WallFLUKA-calculated Activity Profiles in Concrete Wall

0 50 10010-6

10-5

10-4

10-3

10-2 Ee= 25MeV

55Fe 22Na 3H 54Mn 57Co

0 50 10010-6

10-5

10-4

10-3

10-2Ee= 100MeV

55Fe 22Na 3H 54Mn 59Fe

0 50 10010-6

10-5

10-4

10-3

10-2Ee= 1 GeV 3H

55Fe 22Na 60Co 54Mn

0 50 10010-6

10-5

10-4

10-3

10-2 Ee= 10 GeV 55Fe 3H 22Na 54Mn 57Co

Depth (cm)

Depth (cm)Depth (cm)

Depth (cm)

55Fe / 22Na 10

3H / 22Na 5

10-year irradiation and 5-year decay

Act

ivit

y (B

q/g

/W)

55Fe / 22Na 2

Recent Initiatives and EffortsRecent Initiatives and Efforts

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DOE InitiativesDOE Initiatives

• Revision of DOE Order 5400.5 (DOE O 458.1)• Scrap metal management review of NNSA sites• DOE review of SC accelerator labs: SLAC,

TJLAB• NNSA/SC Joint Working Group• Radiological Clearance of Property Workshop,

March 30- April 1, 2010, Las Vegas, Nevada

DOE technical assist visit of SLAC in December, 2009DOE technical assist visit of SLAC in December, 2009

• Review of the property and material clearance processes• Evaluate progress made to develop and implement

enhancements to these processes• DOE team reviewed SLAC radiological material clearance

and occupational radiation safety programs and– Identified five proficiencies with operations that demonstrates

SLAC has continued to make improvements with their site processes and site procedures.

• Compliance with regulations and policies, technical basis, reduction of radiological areas, communication with public, proper survey technique

– Four observations were noted where additional improvements could be made to further enhance SLAC operations

• Property control, Independent verification, Survey instrumentation, Procedures

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Disposition of SLAC MaterialsDisposition of SLAC Materials

• Two memos from DOE:– April 13, 2010 on disposition of concrete shield blocks

– June 9, 2010 on disposition of BaBar detector and PEP-II material

• SLAC Site Office letter of July 1, 2010 – Provides SLAC and SSO with a basis for developing and

implementing a site strategy for disposition of CSB and scrap

metal from BaBar and PEP-II projects, including the release of

scrap metal for recycling

– The significance of the memoranda is that it now provides the SSO

and SLAC with the authority to proceed with the disposition of

certain materials in accordance with the requirements of DOE

Order 5400.5 and SSO approval.

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Joint Activation Working GroupJoint Activation Working Group

• Co-Team Leads • Scott Davis – SC-31.1 HQ• Major David Pugh – NA-171.2 HQ

• SC Representatives• Dennis Ryan BNL• Sayed Rokni SLAC• Don Gregory ORNL•  • NNSA Representatives• Michael Duran LANL• Todd Sundsmo LLNL• Todd Culp SNL

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NNSA/SC joint Working GroupNNSA/SC joint Working Group

• Develop… “Technical Position that will support the release of equipment and material from accelerator facilities and operations where there is potential for induced radioactivity or activated material”

• “This effort shall include all available facility, equipment, material, survey and detection information needed to derive criteria that can be used to determine the areas of and extent of activation.”

• “Criteria being developed should be reasonable and detection activities should be based on current techniques used within the Department and private industry.”

• Volumetric Activation

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Regulations and StandardsRegulations and Standards

• Clearance based on a dose criterion of 1 mrem/y has been recommended: • IAEA Safety Series 89 (1988) • EU Radiation Protection No. 89 (1998)• ANSI N13.12 (1999) – “…Volume Radioactivity Standards for

Clearance”• NCRP-144 “Managing potentially radioactive scrap metal” (2002)• DOE O 458.1 (Draft)

• Clearance levels (in specific activity) for radioisotopes are derived:• IAEA-TECDOC-855 “Clearance levels for radionuclides in solid

materials” (1996)• EU Radiation Protection No. 122 (2000)• ANSI N13.12 (1999)

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Volumetric Release Criteria Volumetric Release Criteria

• Indistinguishable from Background (IFB): the level below which materials are not subject to further regulatory control and can have unrestricted release

• > IFB and ≤ ANSI N13.12 (1999) Screening Levels (dose criterion of <1 mrem per year): as DOE pre-approved Authorized Limits for materials that may be volumetrically activated in accelerators – Allows for consistent technical basis to document compliance with standards,

directives, and Executive Orders

• > ANSI N13.12 (1999) Screening Levels: may be released through the DOE Order 5400.5 Derived Authorized Limit process

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Process KnowledgeProcess Knowledge

• Includes but not limited to: physics of induced radioactivity, facility operations, analytic or Monte Carlo calculations, and/or measurements to determine the types and the levels of induced radioisotopes in accelerators

• Process knowledge allows a graded approach such as the use of Areas of Interest (AOIs) concept – AOIs are areas with potential for activation above background due to

beam losses – Materials in the AOIs are suspect activated– Materials outside the AOIs are not activated (low energy and/or low

intensity beam lines)– Representative measurements to confirm predictions

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Material Release Material Release

• Measurement Protocols demonstrate that induced activity in materials are either Indistinguishable from Background or meet ANSI Screening Levels

• Need Technical Basis to support measurement protocols

• Administrative controls need to be addressed for release above IFB – these can include recipient consent concepts, quality control and verification, and documentation on release processes

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SLAC Measurement ProtocolsSLAC Measurement Protocols

• Measure surfaces of an item

• Measurements using commercially available field instruments and techniques with sufficient sensitivity (e.g., scanning with a 1”x1” scintillator detector)

• Instrument response is indistinguishable from natural background

• The Minimum Detection Activity (MDA) level of the measurements for the “proxy” radioisotopes of interest are no more than the corresponding ANSI Screening Levels (SL), i.e., ∑i (MDAi / SLi) 1

• Laboratory analysis of representative samples as waranetd

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• Goal: Consistent measurement protocols to support for unrestricted release of concrete and metals

• Questionnaire on Measurement protocols• Discussions of issues, show-stoppers and

problems, and solutions that are expected or have occurred in the material release process of each lab

• Deliverable: Benchmark report

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ASW 2010 Workshop Expected Outcome ASW 2010 Workshop Expected Outcome

– Release criteria– Field instruments– Methods (e.g. direct scan, discrete points)– Graded measurement approach based on

MARSSIM/MARSAME considerations– Additional verification measurements (e.g. analytic

sampling, portal gate monitors)– Process knowledge– Record management– Reporting, public information– Technical basis documents– Impact to each site from metal moratorium

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ASW 2010 Workshop –Questionnaire on Measurement protocols ASW 2010 Workshop –Questionnaire on Measurement protocols

33Release Criteria

SLAC Only materials that have non-detectable radioactivity, i.e., indistinguishable from ambient measurement background, can have unrestricted release.o Ludlum 1” NaI: net signal ≤ 2 of background signal of detectors; about 120 cpm in a background of 600 cpm.

(detection limits = a few pCi/g for isotopes of interest).Fermilab See above. Both these threshold values have been determined to correspond to 95 % confidence levels for determining

something to not be radioactive. Our limits represent specific activities of similar magnitude to SLAC’s.JLab Release allowed if no activity detected, and PK indicates little likelihood of hard to detect nuclides.

o Microrem: No detectable signal above ambient background – “detectable” defined to have upper bound of 5 µrem/h net. (sensitivity < 10 pCi/g for nuclides of interest in typical materials)

o Pancake GM: No detectable net signal (“detectable” defined to have upper bound of 100 cpm). Sensitivity assumed equivalent to DOE β-γ contamination limits.

SNS NaI – Less than Lc in a background of less than 8000 cpm. Also need PK that material is uniform composition, no likely pure beta/alpha emitters, and most activated surface is

accessible, OR activation calculation showing total activity less than 1000 dpm (powder), 5000 dpm (solid) or 10000 dpm (H-3).

Pancake – less than 10CFR835 release limits for surface contaminationLBNL For potentially activated materials, only materials that have non-detectable radioactivity, i.e., indistinguishable from

ambient measurement background, can have unrestricted release (because they are non-radioactive material). Ludlum 1” NaI: net signal ≤ background signal Ludlum 2224 w/43-89: net signal ≤ surface activity in our release procedure, which references DOE O5400.5 Surface

Contamination Limits (the same as Authorized Limits)BNL Only steel items with a thickness approx. < 2” or concrete thickness approx. < 4” indicating background only are

candidates for unconditional release. Larger bulk items are considered volumetric release. Volumetric release requires direct scan along with analytical samples.

Volumetric release is specifically authorized by and Radiological Control Division manager or as outlined in a Record of Decision.

LANSCE Only materials with no detectable radioactivity shall be free released without any restrictions. o Based on established LANL/LANSCE NDA release criteria (RP-1 TA-53 DP-312 procedure)

Argonne Use “decision level” labeled on meter to decide if radioactivity is present. Typically 100 cpm above bkgd.

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Verification Measurements:Analytic Sample Measurements

SLAC May include portable gamma spectrometry measurements in the field (detection limits around 1 pCi/g for isotopes of interest).

May include core drill sample measurements with Laboratory gamma spectrometry system with environmental measurement protocol (detection limits around 0.1 pCi/g for isotopes of interest).

Fermilab We have used these same verification techniques. We use field gamma spectroscopy, samples, etc. These are used when we have process knowledge reasons for believing that the activation is nonuniform, etc.

Jlab Conducted for the following reasons:o As part of technical basis study,o If PK suggests potential for significant (> ANSI screening levels) activity that may not be detectable through standard

survey,o Release of liquids, finely divided solids, soil and soil analogues.

Methods may include in-situ gamma spectroscopy, samples counted with lab gamma spec (including swipes, core drillings, liquids, etc.), and lab tritium analysis of swipes, liquids and leachates. Detection sensitivity defined in technical basis documents.

SNS If any criteria not met, refer to Health Physicist for further evaluation, maybe including gamma spec

LBNL Conducted as part of shield block release technical basis study. Conducted when warranted by process knowledge or for specific release and field applications. May include portable gamma spectrometry measurements in the field (detection limits around 1 pCi/g for isotopes of

interest). May include core drill sample measurements with Laboratory gamma spectrometry system with environmental measurement

protocol (detection limits around 0.1 pCi/g for isotopes of interest).BNL Volumetric release would include direct survey and analytical samples. Brookhaven National Laboratory no longer has on site

analytical measurement capability. Samples are sent off site for analysis (detection limits < 0.2 pCi/g for radionuclides of interest).

LANSCE We primarily rely on process knowledge but have gamma spectroscopy capabilities if needed.

Argonne same as SLAC not required, but may be done

Thank youThank you

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Field Instruments

SLAC Volumetric radioactivity - Ludlum 2241 or 18 meter with 4402 detector (1” NaI) or equivalent Surface contamination - Ludlum 2241 with GM pancake or equivalent (e.g., TBM P15).

Fermilab For volume activation, Bicron Analyst with 1.5” X 1.5” NaI probe or Eberline E140 or Ludlum 17704 Frisker Survey Instrument (Pancake GM tube) are used. The Bicron is preferred for detecting volume activation but magnetized materials and stray static magnetic fields from spectrometers, etc. preclude their use in some locations.

Smear samples are also taken as indicated by other reasons.

JLab Volumetric activity: Thermo (Bicron) Microrem with low energy option. Plastic (tissue equivalent) scintillator.

Surface contamination: Pancake GM detector with any appropriate count rate meter.

SNS Volumetric – 2x2 NaI probe with ASP-2e electronics. Surface Contamination – Pancake probe with Bicron Surveyor M

LBNL Volumetric radioactivity: Ludlum 16 meter with 44-2 detector (1” NaI) or equivalent is required. Typically use Ludlum 2221 meter with 44-20 (3” NaI) detector.

Surface contamination: Ludlum 2224 meter with 43-89 (alpha/beta phoswich) or equivalent.

BNL Ludlum 19 micro-R with 1” NaI detector.LANSCE Eberline

o E600-SPA-3 (2X2” NaI)o ESP-1-HP-260 (GM)

Argonne Eberline ASP2e meter with PG2 2mm x 2 inch probe (mini-FIDLER)

SLAC Path forward for FY11SLAC Path forward for FY11

• Complete SLAC release protocol consistent with guidance– Program manual, technical basis document, operating

procedures, document and record management• Material management plan

– Identify components to be released• Develop SSO/SLAC oversight and independent

verification • Develop stakeholder communication and reporting plan• Release large shielding blocks, metals from PEP-II and

BaBar

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FLUKA-calculated Activity Profiles in Concrete WallFLUKA-calculated Activity Profiles in Concrete Wall

Depth (cm)

Act

ivit

y (B

q/g

/W)

• 10-year irradiation and 1-year decay

0 50 10010-6

10-5

10-4

10-3

10-2Ee = 25 MeV

55Fe 22Na 57Co 58Co 54Mn

0 50 10010-6

10-5

10-4

10-3

10-2Ee = 1 GeV 55Fe

3H 22Na 54Mn 57Co

0 50 10010-6

10-5

10-4

10-3

10-2Ee = 100 MeV

55Fe 22Na 57Co 54Mn 3H

0 50 10010-6

10-5

10-4

10-3

10-2Ee = 10 GeV 55Fe

3H 57Co 22Na 54Mn

Surface Maximum

Photonuclear

55Fe / 22Na 10

3H / 22Na 2

Spallation

55Fe / 22Na 2

3838

10-3

10-2

10-1

100

101

0 10 20 30 40 50

Act

ivit

y (B

q/g)

Depth (cm)

10-3

10-2

10-1

100

101

0 10 20 30 40 50

Act

ivit

y (B

q/g)

Depth (cm)

10-3

10-2

10-1

100

101

0 10 20 30 40 50

Act

ivit

y (B

q/g)

Depth (cm)

H-3

Co-60

Eu-152

Cs-134

Mn-54

Na-22

45 MeV 220 MeV 1.3 GeV

Measured Activity Depth Profiles in Concrete

Measurements by Masumoto et al. of KEK at three electron accelerators “Evaluation of radioactivity induced in the accelerator building and its application to decontamination work,” Journal of Radio-analytical and Nuclear Chemistry, 255:3, 2003.

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