epri radiation safety program – 2016 - pwr alara 2 epri radiation safety program – 2016 program...

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EPRI Radiation Safety Program – 2016

Program Goals:Develop tools, technologies, and improvements to operational practices that canEnhance public and worker safetyReduce risks associated with waste management

Radiation Management

& Source Term

Radiological Environmental Protection

Low Level Waste

Low Dose Health Effect

Decommissioning

3© 2016 Electric Power Research Institute, Inc. All rights reserved.

Decommissioning Database (2016 to 2018)

A wealth of experience is available from completed and ongoing decommissioning projects

Experience largely captured in more than 30 EPRI reports

There is a need for a searchable data base for decommissioning experience covering all areas (planning, execution, site characterization and release)

Began development of Wiki-format database in 2016

– Database roll out in 2016

– Adding functionality and content in 2017 and 2018

For more information contact Rick Reid ([email protected])4

© 2016 Electric Power Research Institute, Inc. All rights reserved.

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Radiation Safety Research Focus Areas

ALARA Strategies and TechnologiesCombines source term reduction technologies with typical dose reduction tools and work planning improvements to provide a comprehensive strategy for reducing dose to workers.

Radioactivity Generation and Control (Source Term Reduction) – Joint w/Chem.Understanding radioactivity and radiation field generation and transport processes and tools/technologies to improve control of radioactivity.

Radiation Safety GuidanceDevelopment and maintenance of guidelines, guides and sourcebooks for radiation protection, source term reduction, radiological environmental protection (which includes groundwater), and low level waste.

Radiation Measurements and Dosimetry for Workers and PublicInvestigates advanced radiation detection and monitoring technologies for site and environmental monitoring purposes. In addition, more accurate dose calculation methodologies will beinvestigated to improve the quantification of the dose to workers and the public

* Not prioritized

Effluent and Radwaste MinimizationInvestigates effluent (gaseous, liquid), groundwater remediation, and radwaste minimization technologies and management strategies. Also evaluates the impact to effluent and radwaste programs from changes in plant design or operational factors.

Optimization of Industrial and Radiological Safety (currently unfunded)Includes research related to the development of technologies and strategies that better meet the needs for an integrated approach to worker protection – radiological and industrial hazards.

Benchmarking and Trending (Fundamental)*Maintenance of databases for the Standard Radiation Monitoring Programs (SRMP/BRAC) and the industry low level waste benchmarking database, RadBench™.

Low Dose Radiation Health Effects*Investigates health effects from exposure to ionizing radiation to inform the development of radiation safety standards, radiation protection practices, and communication of risks to workers and the public.

Decommissioning Technology and Strategy*Investigates technologies and strategies to facilitate the development and execution of a safe, efficient, and cost-effective decommissioning program.


ERPI Radiation Safety – Technical Strategy Groups

Groundwater (GW TSG)2015 Products - 3002005565

Low Level Waste (LLW TSG)

Radiation Managements and SourceTerm (RMST TSG)2015 Products - 3002005480, 3002005482,

3002005483, 3002005484Carola Gregorich, [email protected], +1 (650) 855 8917

Karen Kim, [email protected], +1 (650) 855 2190

Karen Kim, [email protected], +1 (650) 855 2190

Highly Interactive & Collaborative Peer Groups6


TSG Membership• 3-Yr Commitment Basis

(in addition to RS Base)

Offers• Knowledge transfer• Influence on research direction• Benchmark of emergent issues• Surveys of practices• Independent assessment

one (1) pre membership period• Access to

• Deliverables• Collaboration SharePoint• Webcasts• Workshops

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How to find out about current, active research projects?


How to find out about current, active research projects?


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How to find published reports? – Path 1




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Radiation Field & Source Term Reduction

are a Team Sport12


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Radiation Fields – Understanding and Planning for Them

RP ALARA

Coolant Cycle Objectives:

1. Steam Cycle – power production

2. Asset protection

3. Reactivity control

Core Management Objectives:

1. Power production

2. Fuel reliability


Materials Objectives:

1. Plant availability – power production

2. Plant reliability

Radiation Fields – Understanding and Planning for Them

RP ALARA

Coolant Cycle Challenges:

1. Species detrimental to assets

2. Maintaininga) reactivity controlb) chemistry conditions for asset protection

Core Management Challenges:

1. CIPS/CILC

2. Entrapped hydrogen induced effects in zirconium materials

3. Mechanical/flow induced effects

4. FME induced effects


Materials Challenges:

1. Corrosion/Erosiona)Uniform/generalb)Flow accelerated c)

2. Wear

PSWCC, IGSCC, IASCC …..

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Let’s Remember:Radiation Field & Source Term Reduction

are a Team Sport15


Can the effectiveness of the team approachto radiation field and dose reduction be improved?


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Radiation Fields – Understanding andImproving the Planning for Them

Today’s approaches– Station and industry initiatives on source term

and radiation field reduction

– Planning, monitoring, and responding

– HIT teams

RP and ALARA’s function in team– Challenge and question other disciplines

– Influence planning – plans need to considerradiation field changes

– Support – educate – remind – coach

Reactive

Move to

Proactive


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Monitoring & Characterizing Radiation Fields Provide Essential Data

for Forensic Analysisfor Asset Protection, Fuel Reliability, and Source Term

Reduction


Cobalt


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What could these reactions indicate?

00 -118776

4.7E10 yr-1

18775

23.83hr18774

1 38.0949 b0

18674 OsReWW(28.43%) n

46Ti 046Sc46Ti(8.25%) n -122

1 83.83d121

1 0.1272 b@ 6 MeV22 0 p

011.4%,-1 99Tc2.43E5yr

88.6%,-199mTc γ

-199Ru4443

99Mo(66.02 hr)421n0.1300 b098Mo(24.19%)42

43

6.02 hr (IT)0

0

182W 0182Ta181Ta(99.988%) n -174

114.74d73

1 8288.08b73 0


Selective Alloy Compositions

Ti <0.40

Inconel® alloy 718 <1.00 17.00-21.00 - <0.0850.00-55.00

(Ni+Co)

2.80-3.30 Bal. <0.35

AlCuMn

Nb+TaTi

0.20-0.80<0.30<0.35

4.75-5.500.65-1.15

Inconel® alloy X750 <1.00 14.0-17.0 - <0.08>70.00 (Ni+Co) - 5.0-9.0 <0.50

AlCuMn

Nb+TaTi

0.40-1.00<0.50<1.00

0.70-1.202.25-2.75

Tungsten, molybdenum, tantalum, and titanium are their activation productsare forensic alloy markers


Alloy Co Cr W C Ni Mo Fe Si Others >0.5%

Stellite™ alloy 6 Bal. 28.5 4.6 1.2 <2.0 <1.0 <2.0 <2.0 <1.0Stellite™ alloy 6B <1.5 <3.0 <2.0 Mn

Stellite™ alloy 6LC Bal. 29 4.5 1.1 <2.0 <1.0 <2.0 <2.0 <1.0

Stellite™ alloy 6HC Bal. 28.5 4.6 1.35 <2.0 <1.0 <2.0 <2.0 <1.0

Stellite™ alloy 12 Bal. 30 8.5 1.45 <2.0 <1.0 <2.0 <2.0 <1.0

Stellite™ alloy 21 Bal. 27.5 — 0.25 2.6 5.4 <2.0 <2.0 <1.0

ULTIMET® Bal. 26 2 0.06 9 5 3 0.3 0.8 Mn

Al 0.40

Inconel® alloy 625 <1.0 20.0-23.0 - <0.1 >58.0 8.0-10.0 >5.0 <0.50 Mn <0.50Nb+Ta 3.15-4.15

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Stellite™ Facts

Stellite™ is a trademarked name of the Deloro Stellite Company (now Kennametal Stellite™).

Stellite™ alloys are non-magnetic, corrosion-resistant cobalt-chromium alloys (invented by Elwood Haynes in early 1900s).– Superior wear and galling characteristics

– Display outstanding hardness and toughness, making them difficult to machine

Stellite™ alloy 6, alloy 12, and alloy 21 are frequently used to hardface valve components in nuclear plants.

Haynes International ULTIMET® alloy is similar to Stellite™ in compositionbut mechanical and welding characteristics are much closer to those of theHASTELLOY® alloys.

Do you know where high cobalt alloys are used in your plant?


Stellite™: Major Source of Cobalt


Valves with Stellite™ seats in systems that flow directly to the reactor– System examples: RHR, CVCS, RWCU, BWR feedwater system, etc.

BWRs are particularly susceptible to cobalt from:– Feedwater control valves, RHR check valves, and main steam isolation valves

– OEM CRBs with pins and rollers fabricated from Stellite™ alloys

– Jet pump wedges and restrainer brackets using Stellite™, particularly when slip joint leakage (and possibly other factors) lead to excessive vibration and subsequent damage

– Some low-pressure turbine designs incorporate welded or brazed Stellite™ alloy 6B or cast Stellite™ erosion shields (“buckets”) on the leading edge of the L-0 (last stage) blades to retard water droplet erosion

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Less Obvious Cobalt Sources

Cobalt co-occurs in copper and nickel minerals/ores - cobalt up to 10% of nickel content.

Alloys containing nickel may have “hidden” cobalt unless specifications limit cobalt content.– Frequently, alloy composition will list the nickel content as nickel plus cobalt without a cobalt limit (e.g.,

Inconel® alloy 751 with >70.0% nickel plus cobalt).– Stainless steels or nickel alloys may contain up to 5% (50,000 ppm) elemental cobalt.– Inconel® / Incoloy® (Special Metals Corp.) are nickel-iron-chromium based alloys used in PWR and BWR. Inconel® alloy 690 and Incoloy® alloy 800 - PWR steam generator tubing (first generations used stainless

steel tubing before alloy 600). EPRI recommendation: cobalt impurity in alloy 690 steam generator tubing be limited to 0.014% average

for the tube bundle with no heat to exceed 0.020% (TR-016743-V2R1).

Cobalt content in stainless steel or nickel base alloys for components located in or near the coreshould be targeted to be lower than 0.05% (500 ppm)

because the high neutron flux causes substantial activation of 59Co to 60Co.

Restrict cobalt content to as low a level as practical with target of 0.02% (200 ppm) or less for all stainless steel or nickel base alloy components.


Other Cobalt Sources


Alloys with >12% cobalt:– Inconel® alloy 617, alloy 640H, alloy 783

– Incoloy® alloy 903, alloy 907, alloy 909

Alloys with up to 5.0% cobalt:– Inconel® alloy N06230, alloy G-3

Alloys with up to 2.5% cobalt:– Inconel® alloy C-276, alloy 22, alloy HX (Co >0.5%)

Alloys with up to 1.0% cobalt:– Inconel® alloy 625/625LCF®, alloy 706, alloy 718/718SPF™, alloy X-750

– Inconel® alloy 625 has been used for PWR control rod cladding– Alloy 718 and alloy X-750 for fuel springs and spacer grids

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Questioning Attitude – are you asking?

How does your utility identify “hidden” cobalt sources?

How does your utility justify the costs of low cobalt replacement components?

What alloys are used in place of Stellite™ alloys?

Are cobalt mass balances used at your plant ?– How do you measure ppt-level cobalt since large volume samples

passed through IX membrane filters will elute metals over time?

– How do you treat LLD values at the ppt level?

– How do you determine reactor internal cobalt sources in mass balances?

The cost of using very low cobalt materials throughout the plant is prohibitive.0.02% cobalt stainless steel costs about eight times that of 0.05% stainless steel.


Silver


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Known Sources of Silver in PWRs

RCCAs: 80% Silver, 15% Indium, 5% CadmiumReactor Control Rod Cluster Assemblies

• Cladding is hardened with wear-resistant coatings:

304SS with chrome plating

Inconel 625 cladding coated with chromiumcarbide (Cr3C2)

Type 316SS hardened by ion-nitriding

• Some hybrid designs have B4C with lower~102 cm containing Ag-In-Cd.


Known Sources of Silver in PWRs

RPV Head Seals

Source: Technetics Group: http://www.techneticsgroup.com/bin/Nuclear.pdf

• Metal O-rings are manufactured from Inconel® alloy 718 or Type 304 stainless steel tubing:

Tubing is plated with pure (99.95%) silver

Elastic core (tubing) with deformable plastic layer (silver) provides durable sealing

Plating can separate from tubing (INPO OE19618, Reactor Vessel Head O-Ring Silver Separation)


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Foreign Materials


Solder, brazing, and welding materials

– Lead (Pb) free solder contains 3% silverhttp://www.mgchemicals.com/products/solder/non-leaded/sn96-4900/

– Brazing filler material contains up to 50% silverhttps://www.wmwa.net/downloads/Silver-Brazing-V6.pdf

– Weld materials in VVERs (Journal of Nuclear Materials 265 (1999) 273-284)

Environmental sources – Ag, an antimicrobial agenthttp://www.nanotechproject.org/cpi/search-products/?title=silver

– Water and air purification http://www.alibaba.com/showroom/nano-silver-water-filter.html

– Paint & Coatings

– High performance apparel

One of many examples - http://pubs.acs.org/doi/abs/10.1021/es7032718

– socks may contain as much as 1.3 mg Ag per gram of sock

– and release as much as 0.65 mg Ag into distilled water

– Food & food packaging

– Make-up water sources

Sources of Silver in PWRs


Recognized sources– Ag-In-Cd control rod material

– RPV head seals–silver plated

– Lead-free solder (3% Ag)

– Brazing filler material (up to 50% Ag)

Emerging sources– Environmental source (makeup

water, coatings, water purification)

– Check valve seat rings

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Makeup Water Sources –Silver, a potential not recognized contaminant?

Silver concentrations range in– Oceans up to 0.03 ppb (http://www.seafriends.org.nz/oceano/seawater.htm)

– Lakes and rivers up to 2 ppb (http://www.atsdr.cdc.gov/ToxProfiles/tp146-c1-b.pdf)

– EPA recommends drinking water do not exceed 100 ppm (0.1 mg/L)(http://water.epa.gov/drink/contaminants/secondarystandards.cfm)

– Lots of environmental and health impact studies are going on

Silver occurrence and abundance on Earth– Continental crust – 50 ppb

– Enriched in hydrothermal fluids – 100 ppm(G.S. Pokrovski et al. / Geochimica et Cosmochimica Acta 106 (2013) 501–523)

Aqueous silver chemistry including under high-temperature continues to be a topic of exploration


Silver Decay Chains 127-year 108mAg (107Ag, 51.8%,

activation) can potentially be detected in samples

and may invoke long-term disposal issues

(NUREG/CR-6567, Low-Level Radioactive Waste Classification, Characterization, and Assessment: Waste Streams and Neutron-Activated Metals)

39.6-sec 109mAg has an 88.032-keV gamma (108Cd, 0.89%, activation)

108Cd activates to 464-day 109Cd, which has no gammas, but feeds 109mAg.

110mAg/110Ag (109Ag, 48.1%,activation) decays to stable 110Cd, 110Cd activates to 48.7-min 111mCd,

which decays to stable 111Cd.

David C. Kocher, Radioactive Decay Data Tables: A Handbook of Decay Data for Application to Radiation Dosimetry and Radiological Assessments, U.S Department of Energy, DOE-TIC-11026, 1981.


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Gammas not from Pure Silver Activationbut Cadmium and Indium Activation


If samples are allowed to decay for several days only:

117mSn (13.60 days),

114mIn (49.51 days),

115Cd (53.46 hours)/115mIn

have a reasonably good change of being quantified.

BUT

Radionuclide Half-Life Decay Chain

Half-Life Photon, keV

Yield, %

Cd-117 2.49 hr In-117m 116.5 min 158.562 ~15.9x(0.917+.015)Cd-117m 3.36 hr In-117 43.8 min 158.562 ~86x0.985Sn-117m 13.60 d 158.562 86.4In-114m 49.51 d 190.27 15.9Cd-117 2.49 hr 273.349 27.9Cd-117 2.49 hr In-117m 116.5 min 315.302 ~19.5x(0.917+.015)Cd-115 53.46 hr In-115m 4.36 hr 336.301 46.7Cd-117 2.49 hr 344.459 17.9

In-116m1 54.15 min 416.99 27.8Cd-115 53.46 hr 527.901 29.1

Cd-117m 3.36 hr In-117 43.8 min 553.00 ~99x0.985Cd-117m 3.36 hr 564.397 14.7In-116m1 54.15 min 818.67 11.6Cd-107 6.50 hr 829.0 100rel

Cd-117m 3.36 hr 1029.06 11.7Cd-117m 3.36 hr 1065.98 23.1In-116m1 54.15 min 1097.21 55.3Cd-117m 3.36 hr 1234.59 11In-116m1 54.15 min In-116 14.1 sec 1293.4 100relIn-116m1 54.15 min 1293.54 84.5Cd-117 2.49 hr 1303.27 18.4

Cd-117m 3.36 hr 1432.91 13.4Cd-117 2.49 hr 1576.62 11.2

Cd-117m 3.36 hr 1997.33 26.2In-116m1 54.15 min 2112.3 15.4

The Fine Print (1)

Neutron capture in Ag-In-Cd control rod material results in– different isotopic conversions take place in the absorber

In Sn and Ag Cd(resonance capture of epithermal neutrons (0.6 eV < E < 0.8 MeV),

– Causing an increasing volume of the absorber as a function of neutron fluence, and

– Swelling can lead to cracks in the cladding, exposing Ag-Cd-In absorber and release in 110mAg.

Sn is a constituent of Zircaloy-4 (~1.2-1.7% tin)– activates to 113Sn (115.1 days), 117mSn (13.60 days), and 125Sn (9.64 days).

Zircaloy-4 guide tubes are still used in some PWRs, even though Zircaloy-4 cladding is no longer used.

The 2.77-year 125Sb is an indication of tin activation:

David C. Kocher, Radioactive Decay Data Tables: A Handbook of Decay Data for Application to Radiation Dosimetry and Radiological Assessments,U.S Department of Energy, DOE-TIC-11026, 1981.


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The Fine Print (2)

Potential for Mis-identification–110mAg characterized at 657.75 keV (94.4%)

– 97Nb at 657.90 keV (98.1%)

96Zr is 2.80% in natural zirconium

has a 0.0229 barn cross-section to form 16.90-hour 97Zr,97Zr decays to 72.1-min. 97Nb:

David C. Kocher, Radioactive Decay Data Tables: A Handbook of Decay Data for Application to Radiation Dosimetry and Radiological Assessments,U.S Department of Energy, DOE-TIC-11026, 1981.


Silver OE examples


Ringhals-3 August-October 2013– Elevated radiation fields of RHR and Containment Spray attributed to 110mAg.

– ICES Report 310988,Increased Dose Rates due to High Amounts of Silver (Ag-110), Sept. 25, 2013

– 12 cracked rods released silver

– 110mAg deposited on cold surfaces

Crystal River-3, February 1998– Reported elevated radiation levels attributed to 110mAg

– ICES 171072,High Pressure Injection Pump Radiation Levels Increased Due to Silver in Reactor Coolant System

– Make-up Pump 1B dose rate increased from 50 mR/hr (contact) to 1400 mR/hr during restart from extended outage.

– Plate-out in cold, high flow areas of High Pressure Injection piping occurred.

– Source thought to be leaking control rod(s), but not positively identified.

TMI in 2015– Ag-110m identified in letdown piping using CZT: ~79% of dose rate

– Seal membrane in decay heat valve DH-C-4B or dropped rod events possible causes

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Antimony


Concerns for Antimony

Generic Detrimental Element/ Material Contacting Final Cleaned Surfaces of Fuel/Fuel Components– Metals and alloys with a melting point less than 700°C

(1292°F)

– Aluminum, antimony, bismuth, cadmium, lithium, magnesium, mercury, indium, lead, potassium, tin, rubidium, sodium, and zinc use prohibited unless approved for reactor coolant chemistry control

Antimony activity can be difficult to removed by ion exchange.


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Properties of Antimony

Natural Isotopes

Melting Point: 630.63°C (1167.13°F)

Oxidation States:– +5, +4, +3, +2, +1, −1, −2, −3 (an amphoteric oxide)

– Sb(III) and Sb(V) are of interest in reactor chemistry and radwaste

Fission Product

The possible deleterious effect on fuel has not been documented in open literature.


Isotope RelativeAtomic Mass

IsotopicComposition

StandardAtomic Weight

51 Sb 121 120.9038157(24) 0.5721(5) 121.760(1)123 122.9042140(22) 0.4279(5)

Activation Products

2.42%, E.C. 122Sn

01n5.7731b 122Sb (2.70 da)0 51

121Sb (57.21%) 97.58% 122Te

50

51

-152

124Te 0124Sb123Sb(42.79%) n -152

60.20d51

1 3.87523b51 0

Sb-121


Sb-123

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