ASTM D5411-21

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Designation: D5411 − 10 (Reapproved 2015) D5411 − 21
Standard Practice for
Calculation of Average Energy Per Disintegration (E¯) for a
Mixture of Radionuclides in Reactor Coolant
This standard is issued under the fixed designation D5411; 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
¯
1.1 This practice applies to the calculation of the average energy per disintegration (E) for a mixture of radionuclides in reactor
coolant water.
1.2 The microcurie (μCi) is the standard unit of measurement for this standard. The values given in parentheses are mathematical
conversions to SI units, which 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
2.1 ASTM Standards:
D1066 Practice for Sampling Steam
D1129 Terminology Relating to Water
D3370 Practices for Sampling Water from Flowing Process Streams
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
2.2 Code of Federal Regulations:
10 CFR 100 Reactor Site Criteria
3. Terminology
3.1 Definitions—Definitions: For definitions of terms used in this practice, refer to Terminology D1129.
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 Dec. 15, 2015Dec. 15, 2021. Published December 2015February 2022. Originally approved in 1993. Last previous edition approved in 20102015
as D5411 – 10.D5411 – 10 (2015). DOI: 10.1520/D5411-10R15.10.1520/D5411-21.
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volume information, refer to the standard’s Document Summary page on the ASTM website.
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D5411 − 21
3.1.1 For definitions of terms used in this standard, refer to Terminologies D1129 and D7902. For terms not defined in this test
method or in Terminologies D1129 and D7902, refer to other published glossaries.
4. Summary of Practice
¯
4.1 The average energy per disintegration, E (pronounced E bar), for a mixture of radionuclides is calculated from the known
¯
composition of the mixture. E is computed by calculating the total beta/gamma energy release rate, in MeV, and dividing it by the
¯
total disintegration rate. The resultant E has units of MeV per disintegration.
5. Significance and Use
5.1 This practice is useful for the determination of the average energy per disintegration of the isotopic mixture found in the
¯
reactor-coolant system of a nuclear reactor (1). The E value is used to calculate a site-specific activity limit for the reactor coolant
system, generally identified asas:
¯
A 5 K/E (1)
limiting
¯
A 5 K/E (1)
limiting
where:
K = a power reactor site specific constant (usually in the range of 50 to 200).
where
K = a power reactor site specific constant (usually in the range of 50 to 200).
The activity of the reactor coolant system is routinely measured, then compared to the value of A . If the reactor coolant
limiting
activity value is less than A then the 2-h radiation dose, measured at the plant boundary, will not exceed an appropriately
limiting
small fraction of the Code of Federal Regulations, Title 10, part 100 dose guidelines. It is important to note that the measurement
of the reactor coolant system radioactivity is determined at a set frequency by use of gamma spectrometry only. Thus, the
¯
radionuclides that go into the calculation of E and subsequently A are only those that are calculatedmeasured using gamma
limiting
spectrometry.
¯
5.2 In calculating E, the energy dissipated by beta particles (negatrons and positrons) and photons from nuclear decay of
beta-gamma emitters. This accounting emitters includes the energy released in the form of energy released from extra-nuclear
transitions in the form of such as X-rays, Auger electrons, and conversion electrons. However, not all radionuclides present in a
¯
sample are included in the calculation of E.
5.3 Individual,Individual nuclear reactor,reactor technical specifications vary and each nuclear operator must be aware of
limitations affecting their plant operation. Typically, radioiodines,iodine radionuclides with half lives half-lives of less than 10 min
(except those in equilibrium with the parent),parent) and those radionuclides,radionuclides identified using gamma spectrometry,
spectrometry with less than a 95 % confidence level,level are not typically included in the calculation. However, the technical
requirements arespecify that the reported activity must account for at least 95 % of the activity after excluding radioiodines and
short-lived radionuclides. There are individual bases for each exclusion.
¯
5.3.1 Radioiodines are typically excluded from the calculation of E because United States commercial nuclear reactors are
required to operate under a more conservative restriction of 1 μCμCi (37 kBq) per gram dose equivalent I (DEI) in the reactor
coolant.
90 63
5.3.2 Beta only emitting Beta-only-emitting radio isotopes (for example, Sr or Ni) and alpha emitting radioisotopes (for
241 239
example, Am or Pu) which comprise a small fraction of the activity, shouldare not be included in the E-bar calculation. These
isotopes are not routinely analyzed for in the reactor coolant, and thuscoolant and, thus, their inclusion in the E-bar calculation is
not representative of what is used to assess the 10 CFR 100 dose limits. Tritium, also a beta only beta-only emitter, should not be
“American National Standard Glossary of Terms,” Nuclear Science and Technology (ANSI N1.1), American National Standards Institute, 1430 Broadway, New York, NY
10018.
The boldface numbers in parentheses refer to a list of references at the end of this practice.
D5411 − 21
included in the calculation. Tritium has the largest activity concentration in the reactor coolant system,system but the lowest beta
particle energy. Thus, its dose contribution is always negligible. However, its inclusion in the E-bar calculation would raise the
value of A , yielding a non-conservative value for dose assessment.
limiting
5.3.3 Excluding radionuclides with half-lives less than 10 min, except those in equilibrium with the parent, has several bases.
5.3.3.1 The first basis considers the nuclear characteristics of a typical reactor coolant. The radionuclides in a typical reactor
coolant have half-lives of less than 4 min or have half-lives greater than 14 min. This natural separation provides a distinct window
for choosing a 10-min half-life cutoff.
5.3.3.2 The second consideration is the predictable time delay, approximately 30 min, which occurs between the release of the
radioactivity from the reactor coolant to its release to the environment and transport to the site boundary. In this time, the
short-lived radionuclides have undergone the decay associated with several half-lives and are no longer considered a significant
¯
contributor to E.
5.3.3.3 A final practical basis is the difficulty associated with identifying short-lived radionuclides in a sample that requires some
significant time, relative to 10 min, to collect, transport, and analyze.
5.3.4 The value of E-bar is usually calculated once every 6 months. However, anytime any time a significant increase in the
activity of the reactor coolant occurs, the value of E-bar should be reassessed to ensure compliance with 10 CFR 100. Such
¯
reassessment should be done any time there is a significant fuel defect that would alter the E value and affect A . The two
limiting
¯
possible causes to reassess the value of E would be:
(1) A significant fuel defect has occurred where the noble gas activity has increased.
(2) A significant corrosion product increase has occurred.
¯
For the case of a fuel defect, the plant staff may need to include new radionuclides not normally used in the calculation of E
239 239
such as U and Np.
6. Interferences
6.1 The analytical determination of the radionuclides used for this calculation is made by gamma ray gamma-ray spectrometry.
Commercially available software is generally used to perform the spectrum analysis and data reduction. However, there can be
significant number of interferences from gamma ray gamma-ray emitters with multiple gamma ray gamma-ray emissions. The user
must carefully select the appropriate interference free gamma ray interference-free gamma-ray energy for each radionuclide in
order to determine accurately the activity of each radionuclide. As a specific example, Mn (t ⁄2 = 2.6 h) has a gamma ray
gamma-ray energy of 847 keV and I (t ⁄2 = 53 min) also has a gamma ray energy of 847 keV. The 847 keV gamma ray is also
the most abundant forof each of these radionulcides.radionuclides. It would be inaccurate to use the 847 keV gamma ray for the
determination offor either of these radionuclides.
7. Sampling
7.1 If samples are collected for analysis in support of this practice, they should be representative of the matrix, be of sufficient
volume to ensure adequate analysis, and be collected in accordance with Practices D1066, D3370, and D3648.
7.2 In addition to the requirements of 7.1, if samples of reactor coolant are required in support of this practice, they should
typically be collected only after a minimum of 2 effective full-power days and a minimum of 20 days of power operation have
elapsed since the reactor was last subcritical for 48 h or longer. Individual nuclear operator technical specifications (or now for
many plants called “technical requirements”) vary and should be reviewed to determine specific requirements.
8. Calibration and Standardization
8.1 Any calibrations and standardizations required in support of this practice should be in accordance with the applicable sections
of Practices D3648 and D7282 and in accordance with the manufacturer’s specifications for the gamma spectrometry system used.
9. Procedure
9.1 Conduct all analyses in support of this practice in accordance with the applicable sections of Practice D3648.
D5411 − 21
9.2 Perform sufficient gamma isotopic gamma-isotopic analyses of the liquid, gaseous, and suspended fractions of the sample to
ensure that at least 95 % of the coolant activity due to gamma emitting gamma-emitting isotopes has been quantified. Samples
should be analyzed at approximately 0.5 h, 2 h, 24 h, and 7 daysd following sample collection. Multiple sample analyses are
required to ensure accurate quantification of the longer-lived isotopes because of masking caused by the high initial activity of
short-lived radionuclides in the sample. If interferences continue to be a concern with the results of the analysis conducted on Day
7, it may be necessary to conduct additional gamma isotopic gamma-isotopic analyses of the sample at approximately 30 days after
collection.
9.3 Sample fractions that are going to be stored for recounting (at 24 h, 7 days,d, or 30 days)d) should be preserved with at least
2 mL of concentrated nitric acid per litre of sample immediately after the sample is taken to preserve the sample geometry. This
mitigates the precipitation of radionuclides or adhesion of radionuclides onto container walls.
9.4 Tabulate the concentrations, uniformly measured in μCi/cc (37kBq/cc
...