ASTM D5411-10(2015)

Standard Practice for Calculation of Average Energy Per Disintegration (—E) for a Mixture of Radionuclides in Reactor Coolant

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Standard Practice for Calculation of Average Energy Per Disintegration (¯E) for a Mixture of Radionuclides in Reactor Coolant

STANDARD published on 15.12.2015

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The information about the standard:

Designation standards: ASTM D5411-10(2015)
Note: WITHDRAWN
Publication date standards: 15.12.2015
SKU: NS-623579
The number of pages: 5
Approximate weight : 15 g (0.03 lbs)
Country: American technical standard
Category: Technical standards ASTM

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Fissile materials

Annotation of standard text ASTM D5411-10(2015) :

Keywords:
average energy per disintegration, disintegration, E-bar, MeV per disintegration, nuclear reactor, radioactivity, reactor coolant, technical specifications,, ICS Number Code 27.120.30 (Fissile materials and nuclear fuel technology)

Additional information

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 5.2 In calculating 5.3 Individual, nuclear reactor, technical specifications vary and each nuclear operator must be aware of limitations affecting their plant operation. Typically, radioiodines, radionuclides with half lives of less than 10 min (except those in equilibrium with the parent), and those radionuclides, identified using gamma spectrometry, with less than a 95 % confidence level, are not typically included in the calculation. However, the technical requirements are 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 μC (37 kBq) per gram dose equivalent ¹³¹I (DEI) in the reactor coolant.

5.3.2 Beta only emitting radio isotopes (for example, ⁹⁰Sr or ⁶³Ni) and alpha emitting radioisotopes (for example, ²⁴¹Am or ²³⁹Pu) which comprise a small fraction of the activity, should not be included in the E-bar calculation. These isotopes are not routinely analyzed for in the reactor coolant, 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 emitter, should not be included in the calculation. Tritium has the largest activity concentration in the reactor coolant 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_limiting, yielding a non-conservative value for dose assessment.

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 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_{1.1 This practice applies to the
calculation of the average energy per disintegration (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 and health practices and determine the applicability of regulatory limitations prior to use.

2. Referenced Documents

10 CFR 100	Reactor Site Criteria Available from Standardization Documents Order Desk, Bldg. 4 Section D, 700 Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.
D1129-13(2020)e2	Standard Terminology Relating to Water (Includes all amendments and changes 2/14/2024).
D7282-21e1	Standard Practice for Setup, Calibration, and Quality Control of Instruments Used for Radioactivity Measurements (Includes all amendments and changes 12/8/2022).
D1066-18e1	Standard Practice for Sampling Steam (Includes all amendments and changes 12/31/2018).
D3370-18	Standard Practices for Sampling Water from Flowing Process Streams
D3648-23	Standard Practices for the Measurement of Radioactivity

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