Shippingport incore instrumentation

[Muti]

The other day I was looking in Wikipedia picture of Shippingport RPV, from picture it looks like it does not have guide tubes stubs for incore flux detectors. Considering the type of fuels it used, was not an incore measurement system a necessity? or the enrichment of fuel made technical limitations in using detectors inside core.

 

[Astronuc]

A lot of the early reactors were built with ex-core detectors.

According to a note with Table 3-1 in this report - http://www5vip.inl.gov/technicalpublications/Documents/2664750.pdf
"The actual core used 16 rod locations for flux wells, so the actual core was loaded with a total of 17,288 rods."

See also - http://www.osti.gov/scitech/servlet...eederReactorcore.(LWBRDevelopmentProgram).pdf

 

[Muti]

Eagle eye...

 

[Muti]

I checked second referred document and at page 44 of the file, there is a figure (2-1), and this figure also show no incore arrangement from bottom.

 

[jim hardy]

http://www.osti.gov/scitech/servlet...eederReactorcore.(LWBRDevelopmentProgram).pdf

probably the same document Astronuc linked
PDF page 125, document page 4-29, fig 4-10 shows tubes for neutron instrumentation. But it doesn't say whether they enter from bottom or top.

They also speak of "activation wires" on PDF page 61 , page 3-10 of document .

One of our shift supervisors came from Shippingport. He described a moving wire system made by (i think) same folks who made our movable fission chamber system, way back in the R&D days . Probably that was it ?

old jim

 

[Astronuc]

http://www.osti.gov/scitech/servlets/purl/5914091-SAaveY/ShippingportoperationswiththeLightWaterBreederReactorcore.(LWBRDevelopmentProgram).pdf

probably the same document Astronuc linked
PDF page 125, document page 4-29, fig 4-10 shows tubes for neutron instrumentation. But it doesn't say whether they enter from bottom or top.

They also speak of "activation wires" on PDF page 61 , page 3-10 of document .

One of our shift supervisors came from Shippingport. He described a moving wire system made by (i think) same folks who made our movable fission chamber system, way back in the R&D days . Probably that was it ?

old jim

I wondered what was meant by flux wells.

From Testing Methods and Calculational Model, Section 2, Flux Wire Activations

"The purpose of these tests was to activate neutron flux wires to obtain axial activation profiles at low power, hot, xenon free conditions and at high power, equilibrium xenon conditions. The flux wire activation data were used to evaluate core symmetry, and radial and axial neutron flux distributions.

Flux wires were inserted into eight flux wells located in seven blanket modules and one reflector module in the LWBR core. See Figure 4-8 of Section 4 for the flux well locations. Following irradiation, the wires were cooled, removed, and transported to the Bettis Atomic Power Laboratory for determination of activation profiles."

Normally, wires are inserted during an outage, and retrieved at end of cycle. Different wires could be retrieved at different times, i.e., after multiple cycles of irradiation, and new wires could be added. However, the wire then only provides an indirect measurement (through activation) of an average flux. Different wires of different compositions have different threshold energies for certain reactions, so they can be used to look at the relative intensities of the flux spectrum.

Ex-core detectors have to be calibrated against thermocouple measurements and flow rates. In-core detectors require penetrations of the RPV, which is a potential leak path in the event of certain accidents. Nevertheless, various reactors were design with RPV penetrations to allow fixed or movable in-core detectors, which allow real-time monitoring of the neutron flux and distribution.

Shippingport certainly had ex-core detectors, but doesn't seem to have had in-core detectors for real-time flux monitoring.

 

[jim hardy]

Shippingport certainly had ex-core detectors, but doesn't seem to have had in-core detectors for real-time flux monitoring.

so the wires aren't moveable...

i read this line and leapt to conclusion they were...

"The purpose of these tests was to activate neutron flux wires to obtain axial activation profiles at low power, hot, xenon free conditions and at high power, equilibrium xenon conditions. The flux wire activation data were used to evaluate core symmetry, and radial and axial neutron flux distributions.

sorry for the red herring. it wasn't by intent.
old jim

 

[Astronuc]

so the wires aren't moveable...

i read this line and leapt to conclusion they were...

sorry for the red herring. it wasn't by intent.

old jim

That's not a red herring. It would confirm that the reactor had no in-core instrumentation, which would require penetrations to the vessel. Instead, the flux wells were locations in a fuel assembly, in which static wires are placed. Activation analysis requires the wire to be removed following reactor shutdown. That's useful to know.

 

[Muti]

Thank you Astronuc . Thank you Jim. "red herring" ... This is what I really like about peoples here. Note: I was very busy for last few days (and still) mostly renaming and rearranging various files, folders, and software on my hard disk...