ASTM D7727-11
(Practice)Standard Practice for Calculation of Dose Equivalent Xenon (DEX) for Radioactive Xenon Fission Products in Reactor Coolant
Standard Practice for Calculation of Dose Equivalent Xenon (DEX) for Radioactive Xenon Fission Products in Reactor Coolant
SIGNIFICANCE AND USE
Each power reactor has a specific DEX value that is their technical requirement limit. These values may vary from about 200 to about 900 μCi/g based upon the height of their plant vent the location of the site boundary, the calculated reactor coolant activity for a condition of 1% fuel defects, and general atmospheric modeling that is ascribed to that particular plant site. Should the DEX measured activity exceed the technical requirement limit the plant enters an LCO requiring action on plant operation by the operators.
The determination of DEX is performed in a similar manner to that used in determining DEI, except that the calculation of DEX is based on the acute dose to the whole body and considers the noble gases 85mKr, 85Kr, 87Kr, 88Kr, 131mXe, 133mXe, 133Xe, 135mXe, 135Xe, and 138Xe which are significant in terms of contribution to whole body dose.
It is important to note that only fission gases are included in this calculation, and only the ones noted in 1. For example 83mKr is not included even though its half life is 1.86 hours. The reason for this is that this radionuclide cannot be easily determined by gamma spectrometry (low energy x-rays at 32 and 9 keV) and its dose consequence is vanishingly small compared to the other, more prevalent krypton radionuclides.
Activity from 41Ar, 19F, 16N, and 11C, all of which predominantly will be in gaseous forms in the RCS, are not included in this calculation.
If a specific noble-gas radionuclide is not detected, it should be assumed to be present at the minimum-detectable activity. The determination of DOSE-EQUIVALENT XE-133 shall be performed using effective dose-conversion factors for air submersion listed in Table III.1 of EPA Federal Guidance Report No. 12, or the average gamma-disintegration energies as provided in ICRP Publication 38 (′′Radionuclide Transformations'') or similar source.
SCOPE
1.1 This practice applies to the calculation of the dose equivalent to 133Xe in the reactor coolant of nuclear power reactors resulting from the radioactivity of all noble gas fission products.
1.2 The values given in parentheses are mathematical conversions to SI units, which are provided for information only and are not considered standard.
1.3 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
General Information
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Standards Content (Sample)
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Designation: D7727 − 11
StandardPractice for
Calculation of Dose Equivalent Xenon (DEX) for Radioactive
Xenon Fission Products in Reactor Coolant
This standard is issued under the fixed designation D7727; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope a factor that normalizes its dose to that of Xe. This practice
is to replace the previous practice of calculating the reactor
1.1 This practice applies to the calculation of the dose
133 coolant Ē calculation when allowed by the plant’s revised
equivalent to Xe in the reactor coolant of nuclear power
technical specifications. The quantity DEX is acceptable from
reactors resulting from the radioactivity of all noble gas fission
a radiological dose perspective since it will result in a limiting
products.
condition of operation (LCO) that more closely relates the
1.2 The values given in parentheses are mathematical con-
non-iodine RCS activity limits to the dose consequence analy-
versions to SI units, which are provided for information only
ses which form their bases.
and are not considered standard.
NOTE 2—It is incumbent on the licensee to ensure that the dose
1.3 Thevaluesstatedininch-poundunitsaretoberegarded
conversion factors (DCFs) used in the determination of DEX are consis-
as standard. The values given in parentheses are mathematical
tent with the DCFs used in the applicable dose consequence analysis used
by the plant in their dose calculation manual for radioactive releases.
conversions to SI units that are provided for information only
and are not considered standard.
5. Significance and Use
2. Referenced Documents
5.1 Each power reactor has a specific DEX value that is
2.1 ASTM Standards:
their technical requirement limit. These values may vary from
D3648 Practices for the Measurement of Radioactivity
about 200 to about 900 µCi/g based upon the height of their
D7282 Practice for Set-up, Calibration, and Quality Control
plant vent the location of the site boundary, the calculated
of Instruments Used for Radioactivity Measurements
reactor coolant activity for a condition of 1% fuel defects, and
general atmospheric modeling that is ascribed to that particular
3. Terminology
plant site. Should the DEX measured activity exceed the
3.1 DOSE-EQUIVALENT XE-133 (DEX),n—shall be that technical requirement limit the plant enters an LCO requiring
action on plant operation by the operators.
Xe concentration (microcuries per gram) that alone would
produce the same acute dose to the whole body as the
5.2 The determination of DEX is performed in a similar
85 85 87
combined activities of noble-gas nuclides mKr, Kr, Kr,
manner to that used in determining DEI, except that the
88 131m 133m 133 135m
Kr, Xe, Xe, Xe, Xe,
calculation of DEX is based on the acute dose to the whole
135 138
Xe, and Xe actually present. 85 85 87 88
body and considers the noble gases mKr, Kr, Kr, Kr,
131m 133m 133 135m 135 138
Xe, Xe, Xe, Xe, Xe, and Xe which are
NOTE 1—This is the general definition of DEX. Each utility may have
adopted modifications to this definition through agreement with the US
significant in terms of contribution to whole body dose.
Nuclear Regulatory Commission (USNRC). The definition as approved
5.3 It is important to note that only fission gases are
for each utility by the USNRC, is the one that should be applied to the
calculations in this method. included in this calculation, and only the ones noted in . For
example 83mKr is not included even though its half life is 1.86
hours. The reason for this is that this radionuclide cannot be
4. Summary of Practice
easily determined by gamma spectrometry (low energy x-rays
4.1 A sample of fresh reactor coolant is analyzed for noble
at 32 and 9 keV) and its dose consequence is vanishingly small
gas activities using gamma ray spectrometry. The individual
compared to the other, more prevalent krypton radionuclides.
activity of each detectable radioactive fission gas is divided by
41 19 16 11
5.4 Activity from Ar, F, N, and C, all of which
predominantly will be in gaseous forms in the RCS, are not
1 included in this calculation.
This practice is under the jurisdiction of ASTM Committee D19 on Water and
is the direct responsibility of Subcommittee D19.04 on Methods of Radiochemical
5.5 If a specific noble-gas radionuclide is not detected, it
Analysis.
should be assumed to be present at the minimum-detectable
Current edition approved May 15, 2011. Published June 2011. DOI: 10.1520/
D7727–11. activity. The determination of DOSE-EQUIVALENT XE-133
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7727 − 11
shall be performed using effective dose-conversion factors for 9.2 An appropriate aliquant of the sample is counted as a
air submersion listed in Table III.1 of EPA Federal Guidance pressurized liquid or degasified and the removed gas counted
Report No. 12, or the average gamma-disintegration energies
on a gamma ray spectrometer immediately after degasification
as provided in ICRP Publication 38 (''Radionuclide Transfor-
occurs.
mations’’) or similar source.
9.3 If a separated gas sample is counted, the method used
6. Interferences
should ensure that noble gas radionuclides are no retained by
the liquid phase. If they are, then the concentration from the
6.1 The analytical determination of the radionuclides used
liquid phase should be included in the calculation in 10.1.
for this calculation is made by gamma ray
...
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