Standard Practice for Calculation of Dose Equivalent Xenon (DEX) for Radioactive Xenon Fission Products in Reactor Coolant

SIGNIFICANCE AND USE
5.1 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.  
5.2 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.  
5.3 It is important to note that only fission gases are included in this calculation, and only the ones noted in Table 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.  
5.4 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.  
5.5 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. 12,3 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 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.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D7727 − 21
Standard Practice for
Calculation of Dose Equivalent Xenon (DEX) for Radioactive
1
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 the same acute dose to the whole body as the combined
85m 85 87 88 131m
activitiesofnoble-gasnuclides Kr, Kr, Kr, Kr, Xe,
1.1 This practice applies to the calculation of the dose
133m 133 135m 135 138
133 Xe, Xe, Xe, Xe, and Xe actually present.
equivalent to Xe in the reactor coolant of nuclear power
reactors resulting from the radioactivity of all noble gas fission
3.1.1.1 Discussion—This is the general definition of DEX.
products.
Each utility may have adopted modifications to this definition
through agreement with the U.S. Nuclear Regulatory Commis-
1.2 The values stated in inch-pound units are to be regarded
sion (U.S. NRC).The definition as approved for each utility by
as standard. The values given in parentheses are mathematical
the U.S. NRC is the one that should be applied to the
conversions to SI units that are provided for information only
calculations in this practice.
and are not considered standard.
1.3 This standard does not purport to address all of the
4. Summary of Practice
safety concerns, if any, associated with its use. It is the
4.1 A sample of fresh reactor coolant is analyzed for noble
responsibility of the user of this standard to establish appro-
gas activities using gamma-ray spectrometry. The individual
priate safety, health, and environmental practices and deter-
activity of each detectable radioactive fission gas is divided by
mine the applicability of regulatory limitations prior to use.
133
a factor that normalizes its dose to that of Xe. This practice
1.4 This international standard was developed in accor-
replaces the previous practice of calculating the reactor coolant
dance with internationally recognized principles on standard-
%
E calculation when allowed by the plant’s revised technical
ization established in the Decision on Principles for the
specifications. The quantity DEX is acceptable from a radio-
Development of International Standards, Guides and Recom-
logical dose perspective since it will result in a limiting
mendations issued by the World Trade Organization Technical
condition of operation (LCO) that more closely relates the
Barriers to Trade (TBT) Committee.
non-iodine RCS activity limits to the dose consequence analy-
ses which form their bases.
2. Referenced Documents
NOTE 1—It is incumbent on the licensee to ensure that the dose
2
2.1 ASTM Standards:
conversion factors (DCFs) used in the determination of DEX are consis-
D3648 Practices for the Measurement of Radioactivity tent with the DCFs used in the applicable dose consequence analysis used
by the plant in their dose calculation manual for radioactive releases.
D7282 Practice for Set-up, Calibration, and Quality Control
of Instruments Used for Radioactivity Measurements
5. Significance and Use
D7902 Terminology for Radiochemical Analyses
5.1 Each power reactor has a specific DEX value that is
their technical requirement limit. These values may vary from
3. Terminology
about 200 to about 900 µCi/g based upon the height of their
3.1 Definitions:
plant vent, the location of the site boundary, the calculated
133
3.1.1 dose-equivalent Xe-133 (DEX), n—shall be that Xe
reactor coolant activity for a condition of 1 % fuel defects, and
concentration(microcuriespergram)thatalonewouldproduce
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
1
This practice is under the jurisdiction ofASTM Committee D19 on Water and
is the direct responsibility of Subcommittee D19.04 on Methods of Radiochemical action on plant operation by the operators.
Analysis.
5.2 The determination of DEX is performed in a similar
Current edition approved Dec. 15, 2021. Published January 2022. Originally
manner to that used in determining DEI, except that the
approved in 2011. Last previous edition approved in 2016 as D7727 – 11 (2016).
DOI: 10.1520/D7727-21.
calculation of DEX is based on the acute dose to the whole
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 85m 85 87 88
body and considers the noble gases Kr, Kr, Kr, Kr,
contact ASTM Customer Service at service@astm.
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D7727 − 11 (Reapproved 2016) D7727 − 21
Standard Practice for
Calculation of Dose Equivalent Xenon (DEX) for Radioactive
1
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
133
1.1 This practice applies to the calculation of the dose equivalent to Xe in the reactor coolant of nuclear power reactors resulting
from the radioactivity of all noble gas fission products.
1.2 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.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2
2.1 ASTM Standards:
D3648 Practices for the Measurement of Radioactivity
D7282 Practice for Set-up, Calibration, and Quality Control of Instruments Used for Radioactivity Measurements
D7902 Terminology for Radiochemical Analyses
3. Terminology
3.1 Definitions:
133
3.1.1 dose-equivalent Xe-133 (DEX), n—shall be that Xe concentration (microcuries per gram) that alone would produce the
85m 85 87 88 131m 133m 133
same acute dose to the whole body as the combined activities of noble-gas nuclides Kr, Kr, Kr, Kr, Xe, Xe, Xe,
135m 135 138
Xe, Xe, and Xe actually present.
3.1.1.1 Discussion—
This is the general definition of DEX. Each utility may have adopted modifications to this definition through agreement with the
U.S. Nuclear Regulatory Commission (U.S. NRC). The definition as approved for each utility by the U.S. NRC is the one that
should be applied to the calculations in this practice.
1
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 Analysis.
Current edition approved Nov. 1, 2016Dec. 15, 2021. Published November 2016January 2022. Originally approved in 2011. Last previous edition approved in 20112016
ɛ1
as D7727 – 11D7727 . DOI: 10.1520/D7727-11R16. – 11 (2016). DOI: 10.1520/D7727-21.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
D7727 − 21
4. Summary of Practice
4.1 A sample of fresh reactor coolant is analyzed for noble gas activities using gamma ray gamma-ray spectrometry. The
133
individual activity of each detectable radioactive fission gas is divided by a factor that normalizes its dose to that of Xe. This
%
practice is to replace replaces the previous practice of calculating the reactor coolant EĒ calculation when allowed by the plant’s
revised technical specifications. The quantity DEX is acceptable from a radiological dose perspective since it will result in a
limiting condition of operation (LCO) that more closely relates the non-iodine RCS activity limits to the dose consequence
analyses which form their bases.
NOTE 1—It is incumbent on the licensee to ensure that the dose conversion factors (DCFs) used in the determination of DEX are consistent with the DCFs
used in the applicable dose consequence analysis used by the plant in their dose calculation manual for radioactive releases.
5. Significance and Use
5.1 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
...

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