Question about Cumulative Fission Yields

mesa

So CFY gives the average number of atoms of a specific nuclide produced from a fission directly plus that from the decay of precursors, so why does thermal U233 have two values for Gallium @ 7.192x10^(-8) and 1.0788x10^(-8)? Is this number dependent on the thermal range the neutrons that hit the nucleus of U233?

Astronuc

Quote by mesa

So CFY gives the average number of atoms of a specific nuclide produced from a fission directly plus that from the decay of precursors, so why does thermal U233 have two values for Gallium @ 7.192x10^(-8) and 1.0788x10^(-8)? Is this number dependent on the thermal range the neutrons that hit the nucleus of U233?

What is the source of the data. Some databases will give a cumulative fission yields for thermal and fast fissions, and some give the fast fission yield at ~1 MeV and/or 14 MeV.

mheslep

For this topic the interest is in thermal neutron fission, i.e. a MSR, just like a light water solid fuel reactor.

mesa

Quote by Astronuc

What is the source of the data. Some databases will give a cumulative fission yields for thermal and fast fissions, and some give the fast fission yield at ~1 MeV and/or 14 MeV.

Just what mheslep said, we are looking at thermal. I got the values for a parent U233 off of this chart for Gallium 69:
http://www-nds.iaea.org/relnsd/vchart/
I don't understand why there are two values there.

I noticed the IAEA definition for CFY's is, "total number of atoms of a specific nuclide produced directly by a fission event and via decay of precursors", (link:http://www-nds.iaea.org/sgnucdat/safeg2008.pdf) but wikepedia says it is per 100 fissions (link:http://www.nucleonica.net/wiki/index...cts_and_Yields), which is correct?

Astronuc

Quote by mesa

Just what mheslep said, we are looking at thermal. I got the values for a parent U233 off of this chart for Gallium 69:
http://www-nds.iaea.org/relnsd/vchart/
I don't understand why there are two values there.

The second value should be the uncertainty. These values are from the European database.

From the JENDL-4.0 database (http://wwwndc.jaea.go.jp/cgi-bin/nuc...0a.cgi?31,72,1) for Ga-72 gives:

Code:

Neutron-induced Fission Yields - Cumulative Fission Yield -
Product  Nuclide  Energy(eV)  Fission Yield  Uncertainty(s)
------------------------------------------------------------
Ga- 69    U-233 (T) 2.53e-02   9.397010e-08   4.234410e-08 
Ga- 71    U-233 (T) 2.53e-02   1.617040e-06   7.289880e-07 

Ga- 72   U-233 (T) 2.53e-02   4.163520e-06   2.662330e-06

Ga 69, 71 are stable.
I added 69 from (http://wwwndc.jaea.go.jp/cgi-bin/nuc...0a.cgi?31,69,1)
and 71 from (http://wwwndc.jaea.go.jp/cgi-bin/nuc...0a.cgi?31,71,1)

I noticed the IAEA definition for CFY's is, "total number of atoms of a specific nuclide produced directly by a fission event and via decay of precursors", (link:http://www-nds.iaea.org/sgnucdat/safeg2008.pdf) but wikepedia says it is per 100 fissions (link:http://www.nucleonica.net/wiki/index...cts_and_Yields), which is correct?

I'd trust the iaea definition, but one should verify with another sources, e.g., US DOE national lab like Brookhaven

Quote by mheslep

For this topic the interest is in thermal neutron fission, i.e. a MSR, just like a light water solid fuel reactor.

LWR have a fast flux. Fast fission accounts for 8 to 10% of fssions in an LWR, although that is in U-238. Likewise, the MSR will have fast fission. The problematic (n,α) reaction in Ni is from fast neutrons; the (n,α) reaction does not occur at thermal energies.

mheslep

Quote by Astronuc

...

LWR have a fast flux. Fast fission accounts for 8 to 10% of fssions in an LWR, although that is in U-238.

Thanks.

Likewise, the MSR will have fast fission.

Would it? Yes there will be fast neutrons, but there would be no U238 in a Th based MSR to fission from fast neutrons.
http://en.wikipedia.org/wiki/Thorium...ctinide_wastes

mesa

Quote by Astronuc

The second value should be the uncertainty. These values are from the European database.

From the JENDL-4.0 database (http://wwwndc.jaea.go.jp/cgi-bin/nuc...0a.cgi?31,72,1) for Ga-72 gives:

Code:

Neutron-induced Fission Yields - Cumulative Fission Yield -
Product  Nuclide  Energy(eV)  Fission Yield  Uncertainty(s)
------------------------------------------------------------
Ga- 69    U-233 (T) 2.53e-02   9.397010e-08   4.234410e-08 
Ga- 71    U-233 (T) 2.53e-02   1.617040e-06   7.289880e-07 

Ga- 72   U-233 (T) 2.53e-02   4.163520e-06   2.662330e-06

Ga 69, 71 are stable.
I added 69 from (http://wwwndc.jaea.go.jp/cgi-bin/nuc...0a.cgi?31,69,1)
and 71 from (http://wwwndc.jaea.go.jp/cgi-bin/nuc...0a.cgi?31,71,1)

I'd trust the iaea definition, but one should verify with another sources, e.g., US DOE national lab like Brookhaven

LWR have a fast flux. Fast fission accounts for 8 to 10% of fssions in an LWR, although that is in U-238. Likewise, the MSR will have fast fission. The problematic (n,α) reaction in Ni is from fast neutrons; the (n,α) reaction does not occur at thermal energies.

Uncertainty, very good.
Those values on your table are slightly different from the table I used, should I stick with iaea values or switch to jaea?

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mesa	Question about Cumulative Fission Yields Tweet So CFY gives the average number of atoms of a specific nuclide produced from a fission directly plus that from the decay of precursors, so why does thermal U233 have two values for Gallium @ 7.192x10^(-8) and 1.0788x10^(-8)? Is this number dependent on the thermal range the neutrons that hit the nucleus of U233?

mheslep Recognitions: Gold Member	For this topic the interest is in thermal neutron fission, i.e. a MSR, just like a light water solid fuel reactor.