Add new entries in C-14 for Tellurium 131 and Neodymium 137

[SibylleK]

Branch

https://github.com/wmo-im/CCT/tree/issue65

Summary and purpose

Request of two additional atmospheric chemical constituents in Common code table C-14.

Action proposed

The team is kindly asked to review and approve the content for inclusion within the next update to the WMO Manual on Codes.

Discussions

We ask for two additional radionuclides:
• Tellurium 131
• Neodymium 137

Detailed proposal

Add in Common Code Table C-14	Code	Meaning	Chemical Formula
30297	Tellurium 131	Te-131
30298	Neodymium 137	Nd-137
30299-39999	Reserved

[sebvi]

looks good to me so I support this proposal

[amilan17]

@amilan17 create branch

[jitsukoh]

@amilan17 can you create a branch and ask @SibylleK to update?

[amilan17]

@SibylleK branch is ready for editing

[sebvi]

@amilan17 : could you let Joerg from TT-WIGOSMD know that we are adding new entries in Common Code Table 14 because we may want to synchronise table 1-01-01 in WMDS repository. I tried to tag him but I don't think it works as he is not part of our team. Thanks

[SibylleK]

@amilan17, branch is updated

[gaochen-larc]

Not much information is available through online search about Nd-137. It seems this isotope does not exist in the natural environment:

In 1970 137Nd was reported in “135mCe and 137mNd: Isomeric States in N = 77 Isotones” by Droste et al. [20]. The Dubna U-300 cyclotron accelerated 18O and 20,22Ne beams which bombarded tellurium and tin targets, respectively. 137Nd was produced in the fusion-evaporation reactions 119Sn(22Ne,4n), 122Sn(20Ne,5n), 122Sn(22Ne,7n), and 126Te(18O,7n). Conversion electron and γ-ray spectrometry was used to identify the isotope. “In all cases, γ-rays of 108, 177, 233 and 285 keV which all decay with the same half-life, T1/2 = 1.60±0.15 s were observed... That the new activity belongs indeed to the nucleide 137Nd is proved by (i) the energy difference of the K and L electron lines of the isomeric transition EKL = 37.0±0.8 keV as compared to the value 36.8 keV expected for Z = 60(Nd), and (ii) the shape of the excitation functions from which the number of evaporated neutrons can be determined” The reported half-life corresponds to an isomeric state and is currently the accepted value for this state. Previously the 55.0(15) m half-life of 136Nd had incorrectly been assigned to 137Nd [16]. A half-life of 35(5) m corresponding to the ground state was reported already in 1935 [21], but no mass assignment was made.

https://people.nscl.msu.edu/~thoennes/2009/neodymium-adndt.pdf

[SibylleK]

Dear @gaochen-larc, Thank you very much for your comment and your investigations regarding Nd-137. Indeed, there seems to be only little easy-to-find information (see below for a few links). However, Nd-137 and Te-131 could be among the radionuclides of potential interest for atmospheric dispersion-modelling, for instance, in the context of the Emergency Response Activity of the WMO: https://community.wmo.int/activity-areas/emergency-response-activities-era (All other radionuclides that are considered relevant by the ET-ERA are already included in C-14.)

Links: IAEA document: https://www.iaea.org/sites/default/files/19/09/en-2019-09.pdf "Grey literature" on properties: https://en.wikipedia.org/wiki/Isotopes_of_tellurium https://en.wikipedia.org/wiki/Isotopes_of_neodymium "

[gaochen-larc]

@SibylleK Thank you very much for the information! I totally can see Nd-137 can be useful to verify the atmospheric dispersion models since it does exist in the natural environment. I think we leave the CAS and PubChem numbers blank. Possibly add a comment to indicate this is a manmade isotope. Comments? Maybe we can close this issue now.

[amilan17]

@SibylleK I think this is ready, unless you want to add a note?