ASTM E1297-08(2013)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: E1297 − 08 (Reapproved 2013)
Standard Test Method for
Measuring Fast-Neutron Reaction Rates by Radioactivation
of Niobium
This standard is issued under the fixed designation E1297; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope E170Terminology Relating to Radiation Measurements and
Dosimetry
1.1 This test method describes procedures for measuring
93 93m
E181Test Methods for Detector Calibration andAnalysis of
reaction rates by the activation reaction Nb(n,n') Nb.
Radionuclides
1.2 This activation reaction is useful for monitoring neu-
E185Practice for Design of Surveillance Programs for
trons with energies above approximately 0.5 MeV and for
Light-Water Moderated Nuclear Power Reactor Vessels
irradiation times up to about 30 years.
E261Practice for Determining Neutron Fluence, Fluence
1.3 With suitable techniques, fast-neutron reaction rates for
Rate, and Spectra by Radioactivation Techniques
neutrons with energy distribution similar to fission neutrons
E262Test Method for Determining Thermal Neutron Reac-
can be determined in fast-neutron fluences above about 10
tion Rates and Thermal Neutron Fluence Rates by Radio-
−2
cm . In the presence of high thermal-neutron fluence rates
activation Techniques
12 −2 −1 93m
(>10 cm ·s ), the transmutation of Nb due to neutron
E844Guide for Sensor Set Design and Irradiation for
capture should be investigated. In the presence of high-energy
Reactor Surveillance, E 706 (IIC)
neutron spectra such as are associated with fusion and spalla-
E944Guide for Application of Neutron Spectrum Adjust-
93m
tion sources, the transmutation of Nb by reactions such as
ment Methods in Reactor Surveillance, E 706 (IIA)
(n,2n) may occur and should be investigated.
E1005Test Method for Application and Analysis of Radio-
metric Monitors for Reactor Vessel Surveillance, E 706
1.4 Procedures for other fast-neutron monitors are refer-
(IIIA)
enced in Practice E261.
E1006Practice for Analysis and Interpretation of Physics
1.5 Fast-neutron fluence rates can be determined from the
Dosimetry Results from Test Reactor Experiments
reaction rates provided that the appropriate cross section
E1018Guide for Application of ASTM Evaluated Cross
information is available to meet the accuracy requirements.
Section Data File, Matrix E706 (IIB)
1.6 The values stated in SI units are to be regarded as
3. Terminology
standard. No other units of measurement are included in this
standard.
3.1 Definitions—The definitions stated in Terminology
E170 are applicable to this test method.
1.7 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4. Summary of Test Method
responsibility of the user of this standard to establish appro-
4.1 High purity niobium is irradiated in a neutron field
priate safety and health practices and determine the applica-
93m 93 93m
producing radioactive Nb from the Nb(n,n') Nb reac-
bility of regulatory limitations prior to use.
tion. The metastable state decays to the ground state by the
2. Referenced Documents
virtual emission of 30 keV gamma rays that are all internally
2.1 ASTM Standards: convertedgivingrisetotheactualemissionoforbitalelectrons
D1193Specification for Reagent Water followed by X rays.
4.2 SourcesoftheirradiatedniobiumarepreparedforXray
ThistestmethodisunderthejurisdictionofASTMCommitteeE10onNuclear
or liquid scintillation counting.
Technology and Applicationsand is the direct responsibility of Subcommittee
93m
E10.05 on Nuclear Radiation Metrology.
4.3 TheXraysemittedasaresultofthedecayof Nbare
Current edition approved Jan. 1, 2013. Published January 2013. Originally
counted, and the reaction rate, as defined in Practice E261,is
approved in 1989. Last previous edition approved in 2008 as E1297–08. DOI:
calculated from the decay rate and irradiation conditions.
10.1520/E1297-08R13.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
4.4 The neutron fluence rate may then be calculated from
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
the appropriate spectral-weighted neutron activation cross
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. section as defined by Practice E261.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1297 − 08 (2013)
5. Significance and Use andhasahalf-lifesufficientlylongtoallowitsuseinverylong
exposures(uptoabout40years).Monitoringlongexposuresis
5.1 Refer to Practice E261 for a general discussion of the
usefulindeterminingthelong-termintegrityofnuclearfacility
determination of decay rates, reaction rates, and neutron
3 components.
fluencerateswiththresholddetectors (1-29). RefertoPractice
E1006, Practice E185 and Guide E1018 for the use and
6. Interferences
application of results obtained by this test method.(30-32)
93m
6.1 Pure niobium in the forms of foil and wire is available
5.2 The half-life of Nb is 5730 6 220 days (33) and has
andeasilyhandledasametal.Whenthinniobiumisirradiated,
a K X-ray emission probability of 0.1099 6 0.0025 per decay
it may become brittle and fragile, thus requiring careful
(33).The K and K X-rays of niobium are at 16.5213–16.152
α β
handling or encapsulation to prevent damage or loss of the
and 18.618–18.953 keV, respectively. The recommended Nb
93m
niobium.RefertoGuideE844fortheselection,irradiation,and
(n,n') Nb cross section comes from the IRDF-90 cross
quality control of neutron dosimeters.
sectioncompendium (34),wasdrawnfromtheRRDF-98cross
section evaluations (35) and is shown in Fig. 1.
6.2 There are some distinct advantages and limitations to
three measurement techniques identified in 5.3.Itisthe
5.3 Chemical dissolution of the irradiated niobium to pro-
responsibility of the user to evaluate these and determine the
duceverylowmass-per-unitareasourcesisaneffectivewayto
optimum technique for the situation.
obtain consistent results. The direct counting of foils or wires
6.2.1 Low mass source X-ray spectrometry advantages
can produce satisfactory results provided appropriate methods
include sufficient energy resolution to eliminate other X-ray
and interpretations are employed. It is possible to use liquid
emissions, stable long life sources, reduced interference fluo-
scintillation methods to measure the niobium activity provided
rescence due to other radionuclides, small and precise back-
the radioactive material can be kept uniformly in solution and
ground corrections, and minimal X-ray source self-absorption
appropriate corrections can be made for interfering activities.
corrections. Limitations are low counting efficiency, complex
5.4 The measured reaction rates can be used to correlate
source preparation, and use of hazardous chemicals.
neutron exposures, provide comparison with calculated reac-
6.2.2 Direct X-ray spectrometry of metal (foil or wire)
tion rates, and determine neutron fluences. Reaction rates can
sourceshastheadvantagesofsimplesourcepreparation,stable
bedeterminedwithgreateraccuracythanfluenceratesbecause
longlifesources,sufficientenergyresolutiontoeliminateother
of the current uncertainty in the cross section versus energy
X-ray emissions, small and precise background corrections,
shape.
and no use of hazardous chemicals. Limitations are low
93 93m
5.5 The Nb(n,n') Nb reaction has the desirable proper-
counting efficiency, large X-ray source self-absorption
tiesofmonitoringneutronexposuresrelatedtoneutrondamage
corrections,largercorrectionsforinterferencefluorescencedue
of nuclear facility structural components. It has an energy
to the other radionuclides, and source geometry control.
response range corresponding to the damage function of steel
6.2.3 Liquid scintillation counting advantages include very
high detection efficiency, reproducible source preparation, and
no source self absorption corrections. Limitations include
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
specialized calibration techniques to reduce interference from
this test method.
93 93m
FIG. 1 IRDF-90 Cross Section Versus Energy for the Nb(n,n') Nb Reaction
E1297 − 08 (2013)
other radionuclides, limited source stability, use of hazardous 8.7 Analytical Paper—Analytical grade filter paper of uni-
chemicals, and disposal of hazardous chemical waste. form thickness (about 0.076 cm) and density (about 8 mg
−2
cm ). The paper can be cut or obtained precut to the desired
7. Apparatus
size (usually between 0.5 and 1.5 cm diameter) that is
compatible with the activity concentration of the solution and
7.1 X-ray Spectrometer, using a Si(Li) detector or a Ge
the counting conditions.The paper should be able to absorb as
detector and a multichannel pulse-height analyzer. For more
much liquid as is necessary and not decompose from the acid.
information, refer to Test Methods E181 and E1005.
TFE-fluorocarbon rings with an inside diameter matching the
7.2 Precision Balance, able to achieve the required accu-
outside diameter of the filter paper disks so they fit together
racy.
with light contact.
7.3 Beakers, 50 mL polyethylene; pycnometer (weighing
8.8 Support and Cover Materials—Thin plastic film and
bottle),50mLpolyethylene;volumetricpipets,10µLto5mL.
plastic tape materials are useful to support and cover the filter
7.4 Gamma Ray Spectrometer, using a Ge detector and a paper sources. They should be strong enough to contain the
multichannel pulse-height analyzer. Refer to Test Method
sourcesandthinenoughtominimizeattenuationoftheXrays.
E181.
8.9 Source Holder—A source holder must be used to accu-
7.5 Liquid Scintillation Counter.
rately and reproducibly position the sources for the counting
geometry to be used. The source holder should be constructed
8. Reagents and Materials
of low density materials such as aluminum or plastic.
8.1 Purity of Reagents—Reagent grade chemicals shall be
8.10 Liquid Scintillation Materials—Vials,emulsionscintil-
used in all tests. Unless otherwise indicated, it is intended that
lant (xylene-based), chelating agent (di-2-ethylhexyl phos-
all reagents conform to the specifications of the Committee on
phoric acid).
Analytical Reagents of theAmerican Chemical Society, where
such specifications are available. Other grades may be used,
9. Procedure
provided it is first ascertained that the reagent is of sufficiently
9.1 Determine the size and shape of the niobium sample
high purity to permit its use without lessening the accuracy of
being irradiated. Consider the convenience in handling and
the determination.
93m
available irradiation space. Ensure that sufficient Nb activ-
8.2 Purity of Water—Unless otherwise indicated, any water
ity will be produced to permit accurate radioassay. Typically,
used shall be understood to mean reagent water as defined by
samples of 0.2 to 20 mg of niobium may be used, but a
93m
Type I of Specification D1193.
preliminary calculation of the expected production of Nb
will aid in selecting the appropriate mass for the irradiation.
8.3 Hydrofluoric Acid—Concentrated (32M) hydrofluoric
acid (HF).
9.2 Accurately weigh the niobium sample being irradiated.
8.4 Nitric Acid—Concentrated (16M) nitric acid (HNO ).
9.3 Encapsulate the niobium sample so that it can be
8.5 Niobium Metal—The purity of the niobium is important retrieved and identified following the irradiation. Record the
in that no impurities (such as tantalum) should be present to sample identification, sample weight, and exact details of the
93m
produce long-lived radionuclides that interfere with the Nb encapsulation. Shroud the niobium with neutron filter material
if necessary. If the thermal-to-fast neutron fluence rate ratio is
activity determination. To avoid problems from tantalum, the
niobium should have the lowest tantalum content possible. high (greater than 5) or the tantalum impurity is high (greater
than 10 ppm), use neutron filter materials, if possible.
Niobium metal in the form of foil and wire with tantalum
content of about 5 ppm (parts per million) or less is obtainable
9.4 Irradiate the niobium samples. Keep an accurate record
and can be used under most conditions. The niobium material
of the irradiation history including neutron level versus time,
should be tested for interfering radioactivity by neutron acti-
starting and ending time of the irradiation, and the periods
vation techniques.
when the neutron level is zero. Record the spatial position of
8.6 Encapsulation Material—The encapsulation material the sample in the irradiation facility.
(such as quartz, stainless steel, aluminum, etc.) should be
9.5 After the irradiation, retrieve and identify the irradiated
selected to prevent corrosion of the niobium during irradiation
sample. Take necessary precautions to avoid personnel over-
and to be compatible with the irradiation environment and
exposure to radiation and the spread of radioactive contamina-
post-irradiation handling. If thermal and epithermal neutron
tion.
filters or shrouds are used, these materials (such as cadmium,
9.6 A waiting time between the end of irradiation and the
tantalum, gadolinium, etc.) must also be compatible with the
92m 95
start of counting may be necessary to allow Nb or Nb, or
encapsulation and irradiation environment.
both, to decay to an insignificant level. Check the samples for
activityfromcontaminationbyothermaterialsorreactions(see
4 Test Method E262) and for any material adhering to the
“ReagentChemicals,AmericanChemicalSocietySpecifications,”Am.Chemi-
cal Soc., Washington, DC. For suggestions on the testing of reagents not listed by sample. Check the weight of the sample. If necessary, clean
theAmericanChemicalSociety,see“ReagentChemicalsandStandards,”byJoseph
and reweigh the sample.
Rosin, D. Van Nostrand Co., Inc., New York, NY, and the “United States
Pharmacopeia.” 9.7 X-Ray Source Preparation and Counting:
E1297 − 08 (2013)
9.7.1 If the metal is being dissolved and reduced to a low corrections made for geometry differences, all of the factors
mass-per-unit area source, dissolve the sample by placing it in thatmayinfluencetheresultsmustbeappropriatelycontrolled.
93m
a preweighed 50 mL polyethylene or TFE-fluorocarbon (non- In this approach, the Nb emission rate may be compared to
wettable) beaker and adding enough concentrated hydrofluoric that of a fluence standard to produce a fluence relative to that
acidtocoverthesample(usuallyabout1to10mLofHF).
...