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BHI Energy

This power point supplements the RP Fundamentals for Junior Task Qualifications Handout. Both should be reviewed to prepare for the exam.

Use of ex function on calculator

Scientific Notation

◦ 0.000000236 = 2.36 E-7 or 2.36 X 10-7

◦ 12,300,000 = 1.23 E7 or 1.23 X107

Protons: +1 (positive charge) Protons & Neutron are Nucleons Neutron: neutral or no charge Electron: -1 (negative charge)

Isotopes – Two or more forms of a given element that have identical atomic numbers and the same or very similar chemical properties but different atomic masses and distinct physical properties.

Examples:◦ Hydrogen (H-1)◦ Deuterium (H-2)◦ Tritium (H-3)◦ All have one proton and chemically the same.

An element always has the same number of protons. An ion is an element with a positive charge because it has lost electron.

This can be expressed as A X Z or simply X-A (4 HE 2 or He-4)

Mass Defect is the amount by which the massof an atomic nucleus is less than the sum of the masses of its constituent particles.

Binding Energy : Mass defect is converted into energy which binds the particles in the nucleus.

Mass–energy equivalence E = mc2

Atomic Mass Unit (AMU) equal to 1/12 of a Carbon 12 atom. Proton = 1.007277 Neutron = 1.008665 Electron = 0.00055 Mass Defect - Carbon 12 = 6.0437 + 6.0520 = 12.0957AMU

Black triangle in lower right corner – fission product of U-235

Gray Square – stable isotope

The Gray Squares (stable isotopes) through the center of the chart is called the “line of stability”.

Radioactive half life is given for unstable isotopes.

Alpha decay◦ Generally occurs in elements with Atomic Number >

80 or Mass > 210. Beta decay◦ Conversion of neutrons to protons and ejection of

beta particle (excess neutrons) Positron decay◦ Conversion of proton to neutron and ejection of B+

particle (neutron deficient) Electron capture◦ proton capture an electron becoming a neutron and

emitting a gamma. (neutron deficient) Gamma emission ◦ Metastable or excited nucleus

Alpha particle is the nucleus of a Helium-4 atom with a +2 charge. Neutron deficient isotopes are to the left / above the line of stability. Excess neutron isotopes are to the right / below the line of stability.

Alpha decay226Ra88 →222Rn86 +4α2

Beta decay210Pb82 →210Bi83 + β- + ṽ

Positron decay57Ni28 →57Co27 + β+ + ν

Electron capture57Ni28 + e-→57Co27 + ν

Gamma emissionAX*Z →AXZ + γ

Take notice of what is ejected. Alpha particle, positron(B+), beta (B-) or gamma. For gamma determine if the nucleus was excited (gamma emission) or if an electron was captured (electron capture).

Photo Electric Effect

Compton Scatter

Pair Production

The type of gamma interaction is dependent on gamma energy.

Low energy photons Formation of an ion pair – Atom with a +1 charge and a free electron (-1).

Scatter photon may go on to interact again. Formation of an ion pair – Atom with a +1 charge and a free electron (-1).

High energy photon normally > 2.5 MEV. Minimum of 1.022 MEV Formation of a positron and electron.

BREMSSTRAHLUNG – “braking radiation“When a high energy beta particle passes close to a heavy nucleus it is deflected sharply by the strong electric field. When the beta particle isdeflected and slowed down it will emit electromagnetic energy in the form of X rays.

The energy of the electromagnetic ray is found to be directly proportional to the beta energy and the atomic weight of the nucleus.

This is not a gamma interaction, but covering for clarification.

Alpha particles - Mass of ~4 AMU. Alpha particles are considered monochromatic, due to the energies are nearly the same at ~5 MeV

Beta particles - Mass << 1 AMU. Spectrum energy - Maximum energies of beta particles extend from about 15 keV to about 15 MeV depending on the nuclide. Average energy is ~1/3 of maximum energy.

Gamma rays have no mass. The g ray energy spectrum is a sharp-line spectrum consisting of definite or discrete energies. The measurements of the energies typically 0.1 - 2 MeV, however energies >> 5 MeV are possible.

Neutrons - Mass ~1 AMU. Neutrons are classified according to their energies.◦ Thermal neutrons (slow neutrons) - energy is approximately 0.025 eV◦ Epithermal neutrons - intermediate energy: 0.5 eV to 10 keV◦ Fast neutrons - High energy: 10 keV to 20 MeV◦ Relativistic neutrons - energies greater than 20 MeV (do not exist in our

reactor)

Relative mass and charge of each. Spectrum energy vs discrete energy vs monochromatic energy

Elastic Scatter

Inelastic Scatter

Absorption

Inelastic scatter can be identified as excitation of the target nucleus.

Curie (Ci) - the amount of ionizing radiation released when an element spontaneously emits energy as a result of the radioactive decay. 2.22 X1012 disintegrations per minute(dpm) 3.7 x 1010 disintegrations per second(dps)

Microcurie (uCi) = 2.22 X 106 dpm.

Millicurie (mCi) = 2.22 X 109 dpm.

Curie based on the activity of 1 gram of radium.

Roentgens (R) - the amount of gamma or x-rays required to produce ions resulting in a charge of 0.000258 coulombs/kilogram of air under standard conditions.

Rad - (radiation absorbed dose) - the amount of energy deposited in any medium (e.g., water, tissue, air). An absorbed dose of 1 rad means that 1 gram of material absorbed 100 ergs of energy.

Rem - used to measure the dose equivalents, which combines the amount of energy with the medical effects of the given type of radiation.

Beta / Gamma = 1Neutron = 3/10Alpha = 20

Quality Factors are based on RBE.

Becquerels (Bq) - 1 is equal to 1disintegration per second

37 billion (3.7 x 1010) Bq equals 1 curie

Gray - the amount of radiation absorbed by an object or person, One gray (Gy) is the international system of units (SI) equivalent of 100 Rad, which is equal to an absorbed dose of 1 Joule/kilogram. An absorbed dose of 0.01 Gymeans that 1 gram of material absorbed 100 ergs of energy.

Sievert - The international system (SI) unit for dose equivalent equal to 1 Joule/kilogram. 1 sievert = 100 rem.

The NRC has stated that they have no plans to change to the SI units.

1 uCi = 2.22 E6 dpm

1mCi = 2.22 E9 dpm

1 Ci = 2.22 E12 dpm

micro (u) – 10 -6

milli (m) – 10 -3

Half life -The time in which one half of the atoms of a particular radioactive substance disintegrate into another nuclear form.

Decay Constant = 0.693 / half life Ensure decay time and decay constant in same units (seconds, minutes, hours, days, years).

If the students in the class each flipped a coin 10 times, the average or mean of the class would be 5 heads and 5 tails. However some students may have 3 heads and 7 tails or 7 heads and 3 tails. This would give a results of 5 + 2. The uncertainty would be two. If the number was closer to 5, there would be less variance or uncertainty.

MDA – sample activity which produces count rate statistically different than background, accounting for efficiency.

MDA is impacted by efficiency, background, geometry, sample volume and count times for both background and sample.

Fission Products

Activation Products

Transuranics

Power ops – neutrons, N-16, Noble Gases Shutdown – Corrosion product activation Failed Fuel – Iodine, Fission Product Gases, Alpha

Most fissions produce two fission products of unequal mass.

Fission products will be created along the Fission Yield Curve. Each fission of U-235 yields approximately 200 MeV. Fissionable – nuclide capable of undergoing fission even with a low probability. Fissile – nuclide capable of undergoing fission from low energy thermal neutrons.

“Liquid Drop” model may be use to explain fission. Critical energy required for fission to occur.

Radionuclide Production Reaction Cr-51 50Cr(nth, g)51Cr Fe-59 58Fe(nth, g)59Fe Mn-56 55Mn(nth, g)56Mn Co-58 58Ni(nf, p)58Co

Radionuclide troduction Reaction

H-3 6Li(n,a)3H

Na-24 23Na(n,g)24Na

Ar-41 40Ar(n,g)41Ar

Radionuclide Production Reaction

N-16 16O(n,p)16N N-17 17O(n,p)17N F-18 18O(p,n)18F N-13 16O(p,a)13N

Activation of corrosion product normally involves metals. Activation of water involves oxygen in the water molecule.

239U, 239Np, 238Pu, 240Pu, 241Pu, 241Am, 242Cm, 243Cm, 244Cm

Transuranics are formed as the result of neutron capture and several sequential decays, such as:

238U(n,g)239U239U B- decays to 239Np239Np B- decays to 239Pu

Transuranic – atomic number greater than 92 - Uranium

Tritium H-3 – Activation of H20 & Lithium Ar-41- may occur outside Rx Vessel C-14 – Waste Gas Systems – pure β emitter I-131/135 – Fission Product - Fuel Damage Co-58/60 - Crud N-16 – RCS and BWR Steam Lines Sr-90 / Cs-135 – Fission Products Kr-85 / Xe-133 – Fission Products

Tritium is a concern because it can migrate through S/G u-tube and cannot be removed by filters or resins. Argon 41 is short lived and can be created outside the core / vessel by leakage neutrons. C-14 is a long lived pure beta emitter found in the waste gas system of PWR and off gas system of a BWR. N-16 is short lived (7 sec) and has a high energy gamma (7 Mev).

Natural Background – Cosmic Rays & Terrestrial Sources

Background / natural radiation is approximately 300 mrem / year.

Deep Dose Equivalent (DDE) – Whole body dose equivalent at a tissue depth of 1 cm (1,000 mg/cm²)

Eye Dose Equivalent – Applies to the external exposure of the lens of the eye, is the dose equivalent at a tissue depth of 300 mg/cm² (0.3cm)

Shallow Dose Equivalent (SDE) - The external exposure of the skin or an extremity taken at a tissue depth of 0.007 cm (7 mg/cm2)

Effective Dose Equivalent (EDE) - The sum of the products of the tissue or organ weighting factors from 10CFR20, and the dose to the corresponding body tissues and organs resulting from the exposure to radiation sources external to the body.

Committed Dose Equivalent (CDE) - The dose equivalent to organs or tissues that will be received from an intake of radioactive material by an individual during the 50-year period following the intake.

Total Effective Dose Equivalent (TEDE) - The sum of the deep dose equivalent (external exposure) and the committed effective dose equivalent (internal exposure).

Committed effective dose equivalent (CEDE) – The sum of the products of the committed dose equivalents for each of the body organs or tissues that are irradiated multiplied by the weighting factors applicable to each of those organs or tissues.

Total organ dose equivalent (TODE)- The sum of the deep-dose equivalent (DDE) and the committed dose equivalent (CDE) to the organ receiving the highest dose.

Committed – deals with internal dose (intakes). Effective – weighting factors used: CEDE EDE TEDE = CEDE+DDE

I@1ft = 6CEN

To determine the gamma radiation field intensity (I) in R/hr at one foot from a radioactive point source use the following equation: C= source activity in Curies (Ci) E = gamma energy in MeV N= number of gammas per disintegration

(photon yield)

If more than one photon energy is given, take the sum of each photon multiplied by its percentage or yield.

Calculation for two 3 Curie sources. Co-60 1.173 MEV (100%) + 1.332 MEV (100%) 6 X 3 Curies X (1.173 + 1.332) X 1.00 = 45.09 R/hr @1ft Cs-137 .662 MEV (85%) 6 X 3 Curies X .662 X .85 = 10.13 R/hr @ 1ft

Inverse square law- radiation intensity is inversely proportional to the square of the distance from the source.

I1 = (d2)2I2 (d1)2

R/hr @ d feet = 6 C E Nd2

3 Curie Cs-137 source at 5 feet. Cs-137 .662 MEV (85%) 6 X 3 Curies X .662 X .85 = 0.405 R/hr @ 5ft 5 2

Gamma – lead, steel, concrete, water

Beta – plastics

Neutron – water or boron

Alpha - paper

When shielding high energy beta you must consider Bremsstrahlung when using lead or other high Z number materials.

The ratio of the total photons at a point to the number arriving there without being scattered.

In thick shielding you must account for buildup which is due to the scattering of radiation in the absorber (Compton Scatter)

This is generally a concern with the design of large permanent shields.

Half Value Layer◦ Lead = 0.49”◦ Steel = 0.85”◦ Concrete = 2.38”◦ Water = 4”

Tenth Value Layer◦ Lead = 1.57”◦ Steel = 2.71”◦ Concrete = 8”◦ Water = 24”

When using temporary shielding we must consider the weight and loading of the piping or

scaffold used to support the shielding.

Engineering evaluation and controls are required.

Gamma rays scattered in air.

This is a concern with spent resin liners or spent fuel canister without shielding over the top.

Type of radiation Quality Factor

(Q)

X-, gamma, or beta radiation 1

Alpha particles, multiple-charged particles, fission fragments and heavy particles of unknown charge

20

Thermal Neutrons 3

Fast Neutrons 10

RBE – Relative Biological Effectiveness

Quality factors are based upon RBE – Relative Biological Effectiveness Alphas have the highest Quality Factor, RBE and Linear Energy Transfer (LET).

The method by which radiation causes damage to human cells is by ionization of atoms in the cells.

Majority of cell is made up of water.

Nucleus Difficult to affix a dose because the nucleus is the most radiosensitive part of the cell. Inhibits the ability of the cell to divide by affecting the DNA and RNA. Without normal DNA the cell cannot produce a duplicate set of chromosomes. The longer division is delayed the greater chance it will die.

Primary Effect ◦ Ionization & Excitation of atoms making up the cell ◦ Produced when the initial interaction of radiation is

with the target atoms in the cell such as those in the DNA

Secondary Effects◦ Formation of free radicals which are very reactive and

can chemically attack target molecules, such as DNA ◦ Occurs with the disassociation of water Water makes up 70 - 80% of the cell Three possible reactions: H interacting with H = H2 OH combining with H = H20 H2 + OH = H2O2

◦ Formation of H2O2 (hydrogen peroxide) can lead to cell death. H2O2 is a harmful oxidizer which poisons the cell

When cells are exposed: There is no damage Cells are damaged but are able to repair the damage and operate normally. Cells are damaged and operate abnormally. Cells die as a result of the damage .

Law of Bergonie and Tribondeau◦ "The radiosensitivity of a tissue is directly

proportional to its reproductive capacity and inversely proportional to its degree of differentiation“.◦ Actively dividing and non-specialized cells.◦ Cells in our bodies that are actively dividing are

more sensitive to ionizing radiation.

Differentiation = specialization

Radiosensitive Tissues: ◦ Germinal (reproductive) cells of the ovary and testis

e.g., spermatogonia

◦ Hematopoietic (bloodforming) tissues: red bone marrow, spleen, lymph nodes, thymus

◦ Basal cells of the skin

◦ Epithelium of the gastrointestinal tract (interstitial crypt cells)

Stochastic Effects ◦ Effects that occur by chance, generally occurring

without a threshold level of dose, whose probability is proportional to the dose and whose severity is independent of the dose. ◦ Two examples of stochastic effects: cancer and

genetic mutations.

Non-Stochastic Effects ◦ The health effects of radiation, the severity of which

vary with the dose and for which a threshold is believed to exist. ◦ If doses received are below the threshold dose, no

effects will occur◦ Examples include: cataracts, skin burns, lowering of

blood cell counts, etc.

Stochastic effects may occur with a single cell damaged, Non stochastic effects typically result from the collective injury of many cells. Stochastic – Non-Threshold Model Non-Stochastic – Threshold Model

LD 50/30, 50% of the general population expected to die in a 30 period without medical care the population, 400 – 500 rad

LD 50/60, 50% of the general population expected to die in a 60 day period without medical care– 200 – 300 rad

Based upon research following WWII atomic bomb use. Updated with Chernobyl data.

Somatic effects - radiation effects such as cancer that occur in the exposed individual, as opposed to genetic effects, which occur in the individual's offspring.

Teratogenic effects are associated with prenatal radiation exposure and include immediate effects (such as fetal death or malformations) or increased risk for cancer later in life.

Chromosomal Aberration - The first signs of blood changes may be seen at 20 Rem

Hematopoietic Syndrome – occurs between 200-1000 rad, affects the blood forming tissue

Gastrointestinal Syndrome – Occurs 1000 –5000 rad, affects the GI tract

Central Nervous System (CNS) Syndrome-Greater than 5000 rad, affects the CNS

Cataracts A cataract is opacity of the lens of the eye A chronic exposure of 600 rad (6 gray) may produce a cataract for high LET radiation Generally symptoms will not appear for years after the exposure Effects may be cumulative Neutrons and gamma are primary hazards Exposures at younger ages increase susceptibility

The site-specific radiological control manual should establish trigger levels requiring formal radiological review of non-routine or complex work activities.

The trigger levels will indicate the level of planning, administrative controls and engineering controls.

10 CFR 20 - The licensee shall use, to the extent practical, procedures and engineering controls based upon sound radiation protection principles to achieve occupational doses and doses to members of the public that are as low as is reasonably achievable (ALARA).

Need to evaluate the overall dose savings from the use of shielding, respirators and engineering controls.

All RP limits set forth by the NRC, are deemed acceptable risk. Acceptable risk assumes there is a benefit for an individual receiving dose. In a power plant that benefit is generation of power. All radiation protection limits are set to limit stochastic effects.

TEDE – 5 Rem/year EDE – 15 Rem/year SDE – 50 Rem/year

Types of dosimeters you typical find in nuclear power plants are either thermoluminescent dosimeter (TLD) or optically stimulated luminescent dosimeter(OSLD).

Both detectors give off visible light when processed. The energy absorbed from radiation is stored in a crystalline material.

The difference is that the TLD requires heat to luminesce (give off light) which is then used to determine dose. The OSLD uses visible light during processing to luminesce.

The major disadvantage of TLDs is that the dosimeter cannot be re-read after processing.

OSL principles of operation: Measures radiation using aluminum oxide crystal detectors also known as OSL material. Electrons in the crystal that have been excited by ionizing radiation jump to the conduction band and are trapped in imperfections. They are released when stimulated by light. Because of the material, this released energy results in the emission of light. Read out process uses green light from either a laser or light emitting diode (LED) array to stimulate the detectors. The resulting blue light emitted by the OSL material is detected and measured by a photomultiplier tube using a high sensitivity photon counting system. A measurement is made of the light intensity released. The light that is released is directly proportional to incident radiation and is used to perform a dose calculation. Shielding of the crystals allows differentiation of types of radiation.

TLD OtERATION TLD's use phosphorescence as their means of detection of radiation. Electrons in some solids can exist in two energy states, called the valence band and the conduction band. The difference between the two bands is called the band gap. Electrons in the conduction band or in the band gap have more energy than the valence band electrons. Normally in a solid, no electrons exist in energy states contained in the band gap. This is a "forbidden region." In some materials, or if impurities are added, defects in the material exist or are made that can trap electrons in the band gap and hold them there. These trapped electrons represent stored energy for the time that the electrons are held. This energy is given up if the electron returns to the valence band. In most materials, this energy is given up as heat in the surrounding material, however, in some materials a portion of energy is emitted as light photons. This property is called luminescence.

Electronic Dosimeter – real time monitoring for dose and dose rate. Alarm functions.

Used in HRA, LHRA & VHRA.Subject to radiofrequency interference.

There are other manufactures and models of EDs, but all have dose and dose rate alarms as well as a digital read out.

Self Reading Pocket Dosimeter (SRPD, SRD, PIC)May go off scale if bumped.

SRPDs may be used when radio interference is a concern.

AREA OF THE BODY/COMPARTMENT COMPARTMENT FACTOR (WC)

Head and neck 0.10

Thorax, above the diaphragm 0.38

Abdomen, including the pelvis 0.50

Upper right arm 0.005

Upper left arm 0.005

Right thigh 0.005

Left thigh 0.005

EDEX = ΣWC DDEC

Head - 50 X 0.10 = 5 mrem Thorax – 75 X 0.38 = 28.5 mrem Abdomen – 100 X 0.50 = 50 mrem Right Upper Arms - 75 X 0.005 = 0.375 mrem Left Upper Arms - 75 X 0.005 = 0.375 mrem Right Thigh - 125 X 0.005 = 0.625 mrem Left Thigh - 125 X 0.005 = 0.625 mrem 85.5 mrem

Determine the cause of the alarm. Determine if the alarm was due to a radiation

or non-radiation event. Obtain dose rate survey CR required for dose or dose rate alarms Estimate worker’s exposure Restrict RCA access

Valid alarms may be caused by worker entering an area which: has not be surveyed. was improperly surveyed. was improperly posted. had changing plant conditions. work was not properly planned.

Lost, Damaged, Suspect Dosimetry◦ If the individual’s DLR(s) is lost, damaged, or

requires processing, restrict the workers RCA access.◦ Obtain the SRD histogram◦ Initiate a CR◦ Estimate worker’s exposure

If an anticipated SRD Dose Rate Alarm is authorized by an RP Supervision: ◦ Perform a Pre-Job briefing and Two Minute Drill to

discuss expected alarms.◦ Ensure the worker has available dose.◦ Provide continuous or remote surveillance◦ RP Log entries required

Station’s will have specific requirements for allowing anticipated Dose Rate Alarms.

Annual limit on intake (ALI) means the derived limit for the amount of radioactive material taken into the body of an adult worker by inhalation or ingestion in a year.

Derived air concentration (DAC) means the concentration of a given radionuclide in air which, if breathed by the reference man for a working year of 2,000 hours under conditions of light work results in an intake of one ALI.

Weighting factor (WT) for an organ or tissue (T) is the proportion of the risk of stochastic effects resulting from irradiation of that organ or tissue to the total risk of stochastic effects when the whole body is irradiated uniformly.

ALI is given in units of uCi. DAC is given in units of uCi/ml.

Solubility Class - Because the removal rate of radionuclides ingested or inhaled into the body can change based on chemical composition, the dose to the worker can change accordingly. ◦ D – days◦ W – weeks◦ Y – years

1 DAC = 2.5 mrem

1 ALI = 5000 mrem

5000 mrem = 2.5 mrem / DAC-hr 2000 DAC-hrs

If the limiting dose is to a specific target organ the ALI value provided in regulations will cite the target organ (e.g. bone surface). Thus, an intake of the identified microcuries, would result in a CDE dose of 50 rem to the identified organ.

If the limiting dose is to the whole body, the resulting dose would be 5 rem, CEDE.

CDE – specific organ or tissue over 50 years CEDE – sum of the individual organ CDEs multiplied by scaling factors.

C0-60 DAC 1E-8 uCi/ml

Air sample results = 3E-8 uCi/ml

Workers in area 3 hrs without respirators.

3E-8 X 3 X 2.5 = 22.5 mRem1E-8

Cs-137 DAC = 6E-8 I-131 DAC = 2E-8

Radioactive half-life (TR) - the time it takes for one half of the radioactive material to decay.

Biological half-life (TB) - The time it takes for one half of the originally deposited radionuclide to be eliminated from the body due to the natural biological process.

Effective half-life (TE) - The time it takes for the activity of a radionuclide in the body to be one half of its original value as a result of the radioactive decay and the biological elimination.

Effective half-life formula: TE = TR x TB / TR + TB

Effective half life 3 day & 7 days = 2.1 days 7 days & 21 days = 5.25 days 7 day & 365 days = 6.87 days

Conditions requiring individual monitoring of internal occupational dose. Each licensee shall monitor the occupational

intake of radioactive material by and assess the committed effective dose equivalent to—◦ Adults likely to receive, in 1 year, an intake in excess of

10 percent of the applicable ALI(s)◦ Minors likely to receive, in 1 year, a committed effective

dose equivalent in excess of 0.1 rem.◦ Declared pregnant women likely to receive, during the

entire pregnancy, a committed effective dose equivalent in excess of 0.1 rem.

◦ Dose is reported using NRC Form 5.

NRC Form 4 – Cumulative Occupational Dose History NRC Form 5 - Occupational Dose Record for a Monitoring Period

Typical pressurized-water reactor

Boundaries – Fuel cladding, RCS, Containment N-16 is isolated to containment by use of delay coils in the letdown and sampling systems to allow the short lived isotope (7 sec) to decay.

Fission Product Boundaries – Fuel Pellet, RCS, Containment

N-16 present in steam lines of BWR.

N-16 is present in steam lines. Neutron leakage from the core causes activation of material outside the core and neutron dose rates in the dry well of BWR and containment of PWRs.

General area dose rate -30 cm from the radiation source or from any surface that radiation penetrates. Important for establishing stay times and estimating of whole body exposures that will aid job planning and establishment of exposure controls.

Contact dose rates are taken by placing the radiation detector housing on the surface being measured. These are important for establishing expected rates of exposure to the extremities.

Radiation postings are based on general area dose rates. RA, HRA and LHRA postings based on dose rate 30 cm from the radiation source or from any surface that radiation penetrates.

Time◦ Mock ups◦ Special tooling

Distance◦ Long handled tools◦ Robotics◦ Remote monitoring

Shielding ◦ Temporary Shielding, Water

Source Term Reduction◦ Flushing hot spots◦ Chemical clean up

Mock up training prior to a task improves performance and reduces time to perform. Long handled tools are used to distance workers from source or to work under water. Source Term Reduction includes stellite reduction, chemical clean up, zinc injection and flushing.

Stellite is the trademarked name for various alloys of chromium and cobalt that are formulated to be wear-resistant. Stellite is used in applications where a tough surface is required for components subject to movement with metal to metal contact. Stellite alloys are corrosion-resistant, non-magnetic, and may be formulated to resist hardening, or annealing or to have extreme wear-resistance. Some metallic parts subject to repetitive metal to metal contact are lined or coated with Stellite.

Co-59 + n →Co-60 (stable target) (activation product)

Stellite is used for valve seats, pump wear rings and check valve pins.

Fixed Contamination - Radioactive surface contamination that is not easily transferred to other personnel or equipment through normal contact.

Loose Contamination - Radioactive surface contamination that is easily transferred to other personnel or equipment through normal contact.

Fixed contamination is measured by direct frisking the surface. Loose contamination is measured by use of a smear or wipe survey.

The presence of Alpha contamination poses a potential internal exposure hazard to personnel if proper monitoring and controls are not in place. The Relative Biological Effectiveness (RBE) of Alpha radiation is higher than that of Beta or Gamma radiation. The RBE quantifies the ability of radiation to cause biological effects such as cancer or cell-death, for equivalent radiation exposure.

Biological effects: gamma = 1 / alpha = 20 DAC values: Co-60 1.00 E-08 uCi/ml Unknown gamma 3.00 E-09 uCi/ml Am-241 3.00 E-12 uCi/ml

Equipment Failures:Plant systems that contain radioactive liquids, solids, or gases (air) can develop leaks to the surrounding area. These leaks are typically found at pipe flanges, sealing surfaces (such as pump seals, manways, handholes), through valve packing or other piping and equipment failures that can release radioactive materials into the surrounding areas. Sealed sources that are used for equipment calibrations or instrumentation source checks can also developed leaks.

Human Errors:Human errors can occur when performing tasks either remotely or hands-on. Operating experience has shown that these errors such as: improper system valve lineup, overfilling of tanks, over pressurization of equipment/systems, improper use of equipment/tools, improper identification of systems/components to be opened (aka breached), and improper handling of radioactive materials.

Maintenance Operations:Performance of maintenance operations often produces contamination by opening systems and components containing airborne or liquid radioactivity. Examples of this would be; maintenance on system components that require grinding, welding or cutting contaminated components.

Grinding on contaminated components is an issue with the generation of loose surface contamination, airborne contamination and the release of alpha emitters which may be contained in the oxide layer.

The definition of cross-contamination is the uncontrolled spreading of radioactive contamination on/into people, places or things.

A major hazard associated with contamination is that often, it may be readily spread. As a result, contamination may be found far from the area where it originated.

Leaching is a phenomenon where, hours or days after decontamination of an item has been performed, the contamination levels have increased. Radioactive material that has been deposited in the pores of the item physically migrates to the surface.

Spent fuel casks and other stainless steel equipment may be sprayed down with DI water prior to being submerged in the spent fuel pool to minimize leaching.

Radiological Work Permit (RWP): identifies radiological conditions, establishes worker protection and monitoring requirements, and contains specific approvals for radiological work activities. The radiological work permit serves as an administrative process for planning and controlling radiological work and informing the worker.

General RWP Specific RWP

Sentinel and HIS-20 are two of the major computer systems used for RWPs, however some sites will have their own software.

◦ Description of work◦ Work area radiological conditions◦ Dosimetry requirements – ED Setpoints◦ Pre-job briefing requirements, as applicable◦ Protective clothing and respiratory protection

requirements◦ Radiological Control coverage requirements and stay

time controls, as applicable◦ Limiting radiological conditions that may void the RWP◦ Special dose or contamination reduction

considerations◦ Special personnel frisking considerations◦ Technical work document number, as applicable◦ Unique identifying number◦ Date of issue and expiration◦ Authorizing signatures.

The Radiation Work Permit (RWP) is an acknowledgement by the worker that they have read, understand and will comply with the radiological requirements for the task they are to perform.

The process for signing onto a RWP may be electronic using a computer system or on paper. The worker’s signature acknowledges that they understand the radiological conditions and will comply with the limitations set forth by the RWP.

10 CFR 20

Tritium H-3 Ar-41 I-131/135 Co-58/60 Sr-90 / Cs-137 Kr-85 / Xe-133

Noble gas sample collected by evacuation of a known volume container (marinelli). Particulate sample is collected by drawing a known volume of air through a filter paper. Iodine sample is collected by drawing a known volume of air through a charcoal cartridge. Tritium sample is collected by drawing a known volume of air through an impinger of demineralized water.

A boundary of the contaminated area.

The access point to the contaminated area.

A double SOP is for Highly Contaminated Areas and Discrete Radioactive Particle Zones/Areas

SOP should be routinely surveyed to ensure contamination has not migrated out of the zone.

Radworkers must notify RP prior to removing items from a CA / HCA.◦ Items may be placed in a bag, container or wrapped

as they are removed from the contaminated area and taken directly to a location established for surveying and labeling/tagging the items/equipment.◦ Items not contained, but under RP control while in a

contaminated area; may be removed from contaminated area as long as it has been decontaminated and proven “Clean” smearable survey has obtained.

Radworkers are taught to notify RP prior to removal of items from a CA in Generic Radworker Training. Double bagged – bagged inside the CA and then placed in another clean bag outside the CA.

Fission product gases◦ Generally short lived◦ Direct vents to plant exhaust ventilation

Iodine◦ Utilize HEPAs with charcoal units

Transuranics◦ Alpha monitoring – air samples and smears◦ Alpha Level 2 & 3 controls

Fission product gases – Krypton & Xenon Iodine will concentrate in the thyroid. Potassium Iodide (KI) may be used to block radioactive iodine from concentrating in the thyroid.

Minimize the materials used for radiological work.

Separate radioactive waste from nonradioactive waste.

Separate compactable material from non-compactable material.

Minimize the amount of mixed waste generated. Mixed waste is waste that contains both radioactive and hazardous materials.

Use good housekeeping techniques.

Sites may utilize a “Green is Clean” program to segregate clean trash within the RCA.

Valves Low point drains Elbows Filters Orifices Floors of cavities, transfer canals, sumps and

tanks

Crud tends to settle out in low points, low flow areas or points where flow changes direction.

Mechanical Filter

Low Point Drain

Gap in Shielding?

U-Bend in Pipe

Valve Body

Electrical Conduit and Junction Boxes: Not likely sources unless sprayed with contaminated fluid.

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