1. 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 Department SLAC National Accelerator Laboratory, U.S.A. DOE Accelerator Safety Workshop, SLAC, August 17-19, 2010,

2. Outline 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

3. Regulatory Background
DOE Order 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 , DOE issued a draft Guide G xx in 2002 for the implementation of the control and release of property that may contain residual radioactive material

4. Secretarial 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

5. PEP-II B Factory at SLAC
HER = 2200 m, LER = 2200 m
HER injection line = 2300 m, LER injection line = 2900 m
Total length of beam line = 9600 m (6.0 miles)
Radioactive components (< 6%)

6. Preliminary Field Surveys: PEP Activation
Gross survey map
Yellow shading represents some items in the area read above background
used Ludlum Model-18 with ”x1” NaI detector

7. Structures from BaBar Detector
Magnet flux return (slabs of steel) and support girders

8. CERN LEP and Detectors

9. SLAC Site Impact Volume (ft3) Area (ft2) Landfill burial Shipping Cost
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

10. Induced Radioactivity in Accelerators
-Induced radioactivity is volumetric with maximum at a surface
-Profile of radionuclides

11. Potential Activation in Electron Accelerators Tunnel11
Potential Activation in Electron Accelerators Tunnel
Bremsstrahlung Photons
Electron Beam Loss
Photonuclear
Spallation
Neutron Capture
High-Energy and Low-Energy Neutrons

12. Beam 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

13. 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

14. Critical and Proxy Radioisotopes
Material
Radionuclide
Half-life
Carbon steel
(Fe, C)
and
Cast iron
(Fe, C, Si, Mn)
22Na (proxy)
2.6 y
54Mn (proxy)
312 d
55Fe (5.9 keV x-ray)
2.73 y
57Co
272 d
Aluminum
22Na
Copper
60Co (proxy)
Concrete
3H (pure beta)
12.3 y
60Co
5.26 y
152Eu, 154Eu
13.5 y, 8.59 y
Radioisotopes with long half-lives are of interest.
Hard-to-measure radioisotopes (3H, 55Fe) emit only beta or low-energy X rays
Proxy radioisotopes (22Na, 54Mn, 60Co) emit high-energy and high-intensity gamma rays
10 Sv/y  ANSI N13.12
Screening Level (SL):
22Na, 54Mn, 60Co: 30 pCi/g
55Fe, 3H: 3000 pCi/g
Detection Limit requirement:
∑i (MDAi / SLi)  1

15. Example of FLUKA Induced Activity Calculations: BaBar Detector at SLAC15
Example of FLUKA Induced Activity Calculations: BaBar Detector at SLAC
Three Floors High,
Thousands of Pieces

16. Volumetric 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

17. Example of FLUKA benchmark – Exp T489 at SLAC
Comparison of the calculated and measured residual activity
Copper sample down beam of the target

18. Radioisotopes for Metals in BaBar
Radioactivity in the BaBar IFR forward steel plug at three decay times
Radioisotope
Half-life
FLUKA-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%)
(SA/SL) for 55Fe is much less than (SA/SL) for 60Co

19. FLUKA-calculated Activity Profiles in Concrete Wall
55Fe / 22Na  10
Depth (cm)
Depth (cm)
Activity (Bq/g/W)
55Fe / 22Na  2
3H / 22Na  5
Depth (cm)
Depth (cm)
10-year irradiation and 5-year decay

20. Recent Initiatives and Efforts

21. DOE 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

22. DOE 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

23. Disposition 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 and SSO approval.

24. Joint Activation Working Group
Co-Team Leads
Scott Davis – SC HQ
Major David Pugh – NA HQ
SC Representatives
Dennis Ryan BNL
Sayed Rokni SLAC
Don Gregory ORNL
NNSA Representatives
Michael Duran LANL
Todd Sundsmo LLNL
Todd Culp SNL

25. NNSA/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

26. Regulations 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 (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)

27. 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 Derived Authorized Limit process

28. Process 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

29. 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

30. SLAC 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

31. ASW 2010 Workshop Expected Outcome
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

32. ASW 2010 Workshop –Questionnaire on Measurement protocols
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

33. Release Criteria
SLAC
Only materials that have non-detectable radioactivity, i.e., indistinguishable from ambient measurement background, can have unrestricted release.
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.
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)
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 dpm (H-3).
Pancake – less than 10CFR835 release limits for surface contamination
LBNL
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 O 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.
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.

34. Analytic Sample Measurements
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:
As part of technical basis study,
If PK suggests potential for significant (> ANSI screening levels) activity that may not be detectable through standard survey,
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.
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

35. Thank you

36. 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 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 (3” NaI) detector.
Surface contamination: Ludlum 2224 meter with (alpha/beta phoswich) or equivalent.
BNL
Ludlum 19 micro-R with 1” NaI detector.
LANSCE
Eberline
E600-SPA-3 (2X2” NaI)
ESP-1-HP-260 (GM)
Argonne
Eberline ASP2e meter with PG2 2mm x 2 inch probe (mini-FIDLER)

37. SLAC 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

38. FLUKA-calculated Activity Profiles in Concrete Wall38
FLUKA-calculated Activity Profiles in Concrete Wall
Surface Maximum
Photonuclear
55Fe / 22Na  10
Activity (Bq/g/W)
Spallation
55Fe / 22Na  2
3H / 22Na  2
Depth (cm)
10-year irradiation and 1-year decay

39. Measured Activity Depth Profiles in Concrete39
Measured Activity Depth Profiles in Concrete
220 MeV
45 MeV
1.3 GeV
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.