Selenium-79: Difference between revisions

Selenium-79, ⁷⁹Se
General
Symbol	79Se
Names	selenium-79, 79Se, Se-79
Protons (Z)	34
Neutrons (N)	45
Nuclide data
Natural abundance	trace
Half-life (t1/2)	327000±28000 years
Spin	7/2+
Excess energy	−75917.46±0.22 keV
Binding energy	8695.592±0.003 keV
Decay products	79Br
Decay modes
Decay mode	Decay energy (MeV)
Beta decay	0.1506
	Isotopes of selenium ; Complete table of nuclides

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Selenium-79 is a radioisotope of selenium present in spent nuclear fuel and the wastes resulting from reprocessing this fuel. It is one of only seven long-lived fission products. Its fission yield is low (about 0.04%), as it is near the lower end of the mass range for fission products. Its half-life has been variously reported as 650,000 years, 65,000 years, 1.13 million years, 480,000 years, 295,000 years, 377,000 years and most recently with best current precision, 327,000 years.^[1]^[2]

⁷⁹Se decays to ⁷⁹Br by emitting a beta particle with no attendant gamma radiation (i.e., 100% β decay). This complicates its detection and liquid scintillation counting (LSC) is required for measuring it in environmental samples. The low specific activity (5.1 × 10⁸ Bq/g) and relatively low energy (151 keV) of its beta particles have been said to limit the radioactive hazards of this isotope.^[3]

Performance assessment calculations for the Belgian deep geological repository estimated ⁷⁹Se may be the major contributor to activity release in terms of becquerels (decays per second), "attributable partly to the uncertainties about its migration behaviour in the Boom Clay and partly to its conversion factor in the biosphere." (p. 169).^[4] However, "calculations for the Belgian safety assessments use a half-life of 65 000 years" (p. 177), much less than the currently estimated half-life, and "the migration parameters ... have been estimated very cautiously for ⁷⁹Se." (p. 179)

Neutron absorption cross sections for ⁷⁹Se have been estimated at 50 barns for thermal neutrons and 60.9 barns for resonance integral.^[5]

Selenium-80 and selenium-82 have higher fission yields, about 20 times the yield of ⁷⁹Se in the case of uranium-235, 6 times in the case of plutonium-239 or uranium-233, and 14 times in the case of plutonium-241.^[6]

Mobility of selenium in the environment

Due to redox-disequilibrium, selenium could be very reluctant to abiotic chemical reduction and would be released from the waste (spent fuel or vitrified waste) as selenate (SeO^2–
₄), a soluble Se(VI) species, not sorbed onto clay minerals. Without solubility limit and retardation for aqueous selenium, the dose of ⁷⁹Se is comparable to that of ¹²⁹I. Moreover, selenium is an essential micronutrient as it is present in the catalytic centers in the glutathione peroxidase, an enzyme needed by many organisms for the protection of their cell membrane against oxidative stress damages; therefore, radioactive ⁷⁹Se can be easily bioconcentrated in the food web. In the presence of nitrate (NO^–
₃) released in deep geological clay formations by bituminized waste issued from the spent fuel dissolution step during their reprocessing, even reduced forms of selenium could be easily oxidised and mobilised.^[7]

Long-lived fission products
v
t
e
Nuclide	t_1⁄2	Yield	Q^{[a 1]}	βγ
	(Ma)	(%)^{[a 2]}	(keV)
⁹⁹Tc	0.211	6.1385	294	β
¹²⁶Sn	0.230	0.1084	4050^{[a 3]}	βγ
⁷⁹Se	0.327	0.0447	151	β
¹³⁵Cs	1.33	6.9110^{[a 4]}	269	β
⁹³Zr	1.53	5.4575	91	βγ
¹⁰⁷Pd	6.5	1.2499	33	β
¹²⁹I	16.14	0.8410	194	βγ
^ Decay energy is split among β, neutrino, and γ if any. ^ Per 65 thermal neutron fissions of ²³⁵U and 35 of ²³⁹Pu. ^ Has decay energy 380 keV, but its decay product ¹²⁶Sb has decay energy 3.67 MeV. ^ Lower in thermal reactors because ¹³⁵Xe, its predecessor, readily absorbs neutrons.

References

^ "Home". Ptb.de. 22 June 2017. Retrieved 2017-07-14.
^ Jörg, G., Bühnemann, R., Hollas, S., Kivel, N., Kossert, K., Van Winckel, S., Lierse v. Gostomski, Ch. Applied Radiation and Isotopes 68 (2010), 2339–2351
^ "ANL factsheet" (PDF). Ead.anl.gov. Archived from the original (PDF) on 2004-06-15. Retrieved 2017-07-14.
^ Marivoet; et al. (2001). "Safir-2 report" (PDF). Nirond.be. Retrieved 2017-07-14.
^ "Archived copy". Archived from the original on 2011-06-05. Retrieved 2008-05-11.{{cite web}}: CS1 maint: archived copy as title (link)
^ "Nuclear Data for Safeguards". Nds.iaea.org. Retrieved 2017-07-14.
^ Wright, Winfield G. (1999-07-01). "Oxidation and mobilization of selenium by nitrate in irrigation drainage". J. Environ. Qual. 28 (4): 1182–1187. doi:10.2134/jeq1999.00472425002800040019x. Retrieved 2008-05-11.

@@ Line 1: / Line 1: @@
-{{Long-lived fission products}}
+{{Short description|Long-lived radioisotope of selenium}}
+{{Infobox isotope
-'''Selenium-79''' is a [[radioisotope]] of [[selenium]] present in [[spent nuclear fuel]] and the [[nuclear waste|wastes]] resulting from [[nuclear reprocessing|reprocessing]] this fuel. It is one of only 7 [[long-lived fission product]]s. Its [[fission product yield|yield]] is low (about 0.04%) as it is near the lower end of the mass range for [[fission products]]. Its [[halflife]] has been variously reported as 650,000 years, 65,000 years, 1.13 million years, 480,000 years, and most recently, 295,000 years. <ref>[http://www.iop.org/EJ/abstract/0256-307X/18/6/311 Remeasurement of the Half-Life of 79Se with the Projectile X-Ray Detection Method<!-- Bot generated title -->]</ref>
+ | alternate_names =
+ | symbol = Se
+ | mass_number= 79
+ | mass =
+ | num_neutrons =45
+ | num_protons = 34
+ | abundance = [[trace radioisotope|trace]]
+ | halflife = {{val|327,000|28,000|u=years}}
+ | image =
+ | decay_product = bromine-79
+ | decay_symbol = Br
+ | decay_mass = 79
+ | decay_mode1 = [[Beta decay]]
+ | decay_energy1 = 0.1506
+ | decay_mode2 =
+ | decay_energy2 =
+ | decay_mode3 =
+ | decay_energy3 =
+ | decay_mode4 =
+ | decay_energy4 =
+ | parent =
+ | parent_symbol =
+ | parent_mass =
+ | parent_decay =
+ | parent2 =
+ | parent2_symbol =
+ | parent2_mass =
+ | parent2_decay =
+ | spin = 7/2+
+ | excess_energy = {{val|−75917.46|0.22}}
+ | binding_energy = {{val|8695.592|0.003}}
+}}
+'''Selenium-79''' is a [[radioisotope]] of [[selenium]] present in [[spent nuclear fuel]] and the [[nuclear waste|wastes]] resulting from [[nuclear reprocessing|reprocessing]] this fuel. It is one of only seven [[long-lived fission product]]s. Its [[fission product yield|fission yield]] is low (about 0.04%), as it is near the lower end of the mass range for [[fission products]]. Its [[half-life]] has been variously reported as 650,000 years, 65,000 years, 1.13 million years, 480,000 years, 295,000 years, 377,000 years and most recently with best current precision, 327,000 years.<ref>{{cite web|url=http://www.ptb.de/en/org/6/nachrichten6/2010/60710_en.htm|title=Home|date=22 June 2017|website=Ptb.de|accessdate=2017-07-14}}</ref><ref>Jörg, G., Bühnemann, R., Hollas, S., Kivel, N., Kossert, K., Van Winckel, S., Lierse v. Gostomski, Ch. ''Applied Radiation and Isotopes'' '''68''' (2010), 2339–2351</ref>
-Se-79 decays by emitting a [[beta particle]] with no attendant [[gamma radiation]].  The low [[specific activity]] and relatively low energy of its beta particle have been said to limit the radioactive hazards of this isotope.<ref>[http://www.ead.anl.gov/pub/doc/selenium.pdf ANL factsheet]</ref>
+<sup>79</sup>Se decays to <sup>79</sup>Br by emitting a [[beta particle]] with no attendant [[gamma radiation]] (i.e., 100%&nbsp;''β'' decay). This complicates its detection and [[liquid scintillation counting]] (LSC) is required for measuring it in environmental samples. The low [[specific activity]] ({{nowrap|5.1 × 10<sup>8</sup> Bq/g}}) and relatively low energy (151&nbsp;keV) of its beta particles have been said to limit the radioactive hazards of this isotope.<ref>{{cite web|url=http://www.ead.anl.gov/pub/doc/selenium.pdf|title=ANL factsheet|website=Ead.anl.gov|accessdate=2017-07-14|url-status=dead|archiveurl=https://web.archive.org/web/20040615114154/http://www.ead.anl.gov/pub/doc/selenium.pdf|archivedate=2004-06-15}}</ref>
-Performance assessment calculations for the Belgian [[deep geological repository]] estimated <sup>79</sup>Se may be the major contributor to activity release in terms of [[becquerel]]s (decays per second), "attributable partly to the uncertainties about its migration behaviour in the Boom Clay and partly to its conversion factor in the biosphere." (p. 169)<ref name="safir">http://www.nirond.be/engels/PDF/Safir2_apercutech_eng.pdf Marivoet et al. (2001) Safir-2 report. Ondraf/Niras</ref>. However, "calculations for the Belgian safety assessments use a half-life of 65 000 years" (p. 177), much less than the currently estimated halflife, and "the migration parameters ... have been estimated very cautiously for <sup>79</sup>Se." (p. 179)
+Performance assessment calculations for the Belgian [[deep geological repository]] estimated <sup>79</sup>Se may be the major contributor to activity release in terms of [[becquerel]]s (decays per second), "attributable partly to the uncertainties about its migration behaviour in the Boom Clay and partly to its [[conversion factor]] in the [[biosphere]]." (p.&nbsp;169).<ref name="safir">{{cite web|url=http://www.nirond.be/engels/PDF/Safir2_apercutech_eng.pdf|format=PDF|author=Marivoet |display-authors=etal |date=2001|title=Safir-2 report|website=Nirond.be|accessdate=2017-07-14}}</ref> However, "calculations for the Belgian safety assessments use a half-life of 65 000 years" (p.&nbsp;177), much less than the currently estimated half-life, and "the migration parameters ... have been estimated very cautiously for <sup>79</sup>Se." (p.&nbsp;179)
-[[Neutron absorption]] [[cross section]]s for <sup>79</sup>Se have been estimated at 50 barns for [[thermal neutrons]] and 60.9 barns for [[resonance integral]]. <ref>http://www-nds.iaea.org/j33/data/comments/za034079.html</ref>
+[[Neutron absorption]] [[Absorption cross section|cross section]]s for <sup>79</sup>Se have been estimated at 50 [[Barn (unit)|barns]] for [[thermal neutrons]] and 60.9 barns for [[resonance integral]].<ref>{{cite web |url=http://www-nds.iaea.org/j33/data/comments/za034079.html |title=Archived copy |accessdate=2008-05-11 |url-status=dead |archiveurl=https://web.archive.org/web/20110605112920/http://www-nds.iaea.org/j33/data/comments/za034079.html |archivedate=2011-06-05 }}</ref>
-Se-80 and Se-82 have higher fission yields, about 20 times the yield of Se-79 in the case of U-235, 6 times in the case of Pu-239 or U-233, and 14 times in the case of Pu-241.<ref>[http://www-nds.iaea.org/sgnucdat/c1.htm Nuclear Data for Safeguards<!-- Bot generated title -->]</ref>
+Selenium-80 and [[selenium-82]] have higher [[fission product yield|fission yields]], about 20 times the yield of <sup>79</sup>Se in the case of [[uranium-235]], 6 times in the case of [[plutonium-239]] or [[uranium-233]], and 14 times in the case of [[plutonium-241]].<ref>{{cite web|url=http://www-nds.iaea.org/sgnucdat/c1.htm|title=Nuclear Data for Safeguards|website=Nds.iaea.org|accessdate=2017-07-14}}</ref>
 ==Mobility of selenium in the environment==
-Due to redox-disequilibrium, selenium could be very reluctant to chemical reduction and would be released from the waste (spent fuel or vitrified waste) as soluble selenate, a species not sorbed onto clay minerals. Without solubility limit and retardation for aqueous selenium, the dose of <sup>79</sup>Se is comparable to that of <sup>129</sup>I. Moreover, selenium is an essential micronutrient for many organisms (protection of cell membrane against oxidative damages) and can be easily bioconcentrated in the food chain. In the presence of nitrate, even reduced forms of selenium could be easily oxidised and mobilised.<ref>
+Due to [[redox|redox-disequilibrium]], selenium could be very reluctant to [[abiotic]] chemical reduction and would be released from the waste (spent fuel or vitrified waste) as [[selenate]] ({{Chem|Se|O|4|2–}}), a soluble Se(VI) species, not [[sorption|sorbed]] onto [[clay minerals]]. Without [[solubility|solubility limit]] and [[retardation factor|retardation]] for aqueous selenium, the dose of <sup>79</sup>Se is comparable to that of <sup>129</sup>I. Moreover, selenium is an essential [[micronutrient]] as it is present in the catalytic centers in the [[glutathione peroxidase]], an [[enzyme]] needed by many organisms for the protection of their  [[cell membrane]] against [[oxidative stress]] damages; therefore, radioactive <sup>79</sup>Se can be easily [[bioconcentration|bioconcentrated]] in the [[food web]]. In the presence of [[nitrate]] ({{Chem|N|O|3|–}}) released in deep geological clay formations by [[bitumen|bituminized]] waste issued from the spent fuel dissolution step during their reprocessing, even reduced forms of selenium could be easily [[oxidation|oxidised]] and mobilised.<ref>
 {{Cite journal
+| doi = 10.2134/jeq1999.00472425002800040019x
 | last = Wright
 | first = Winfield G.
@@ Line 23: / Line 58: @@
 | date = 1999-07-01
 | url = http://jeq.scijournals.org/cgi/content/abstract/joenq;28/4/1182
-| month = Jul
-| day = 01
 }}
 </ref>
+{{Long-lived fission products}}
 ==References==
@@ Line 33: / Line 68: @@
 ==See also==
 *[[Isotopes of selenium]]
-*[http://www.ead.anl.gov/pub/doc/selenium.pdf ANL factsheet]
+*[https://web.archive.org/web/20040615114154/http://www.ead.anl.gov/pub/doc/selenium.pdf ANL factsheet]
 *[http://www.rsc.org/publishing/journals/JA/article.asp?doi=b209253k Journal of Analytical Atomic Spectrometry]
-[[Category:Selenium]]
-[[Category:Isotopes]]
 [[Category:Fission products]]
 [[Category:Isotopes of selenium]]
 [[Category:Radioactive waste]]