Monday, July 19, 2010

The Germans, among others, have killed Baker-Just.

The Germans, among others, have killed Baker-Just.

Investigations by P. Hofmann and V. Noak at Forschungszentrum Karlsruhe reveal that the Baker-Just equation is non-conservative for calculating the temperature at which runaway oxidation will occur in a LOCA. Their report is, Physico-Chemical Behavior of Zircaloy Fuel Rod Cladding Tubes During LWR Severe Accident Reflood, Part I: Experimental results of single rod quench experiments, FZKA 5846, Institut für Materialforschung, Projekt Nukleare Sicherheitsforschung, Mai 1997. They report:

A series of separate-effects tests is being carried out on Zircaloy PWR fuel rod cladding to study the enhanced oxidation which can occur on quenching. In these tests, performed in the QUENCH rig, single tube specimens are heated by induction to a high temperature and then quenched by water or rapidly cooled down by steam injection.

No significant temperature excursion during quenching occurred such as had been observed for example in the quenched (flooded) CORA-bundle tests /4, 5/. This absence of any temperature escalation is believed to be due to the high radiative heat losses in the QUENCH rig.

And in, “CORA Experiments on the Materials Behavior of LWR
Fuel Rod Bundles at High Temperatures,” P. Hofmann, S. Hagen, G. Schanz, G. Schumacher, L. Sepold, report:

The critical temperature above which uncontrolled temperature escalation takes place due to the exothermic zirconium/steam reaction crucially depends on the heat loss from the bundle; i.e., on bundle insulation. With the good bundle insulation in the CORA test facility, temperature escalation starts between 1100 and 1200°C (2012 to 2192°F), giving rise to a maximum heating rate of 15 K/sec.

Mark Edward Leyse has initiated the following:

Mark E. Leyse 2.206 Petition to Lower the Licensing Basis Peak Cladding Temperature of Vermont Yankee in Order to Provide Necessary Margin of Safety in Event of LOCA ML101610121

Footnote 8, page 8 of the above 2.206 Petition is as follows:

Data from multi-rod (assembly) severe fuel damage experiments (e.g., the LOFT LP-FP-2 experiment) indicates that the Baker-Just and Cathcart-Pawel equations are both non-conservative for calculating the temperature at which an autocatalytic (runaway) oxidation reaction of Zircaloy would occur in the event of a LOCA. This, in turn, indicates that the Baker-Just and Cathcart-Pawel equations are both non-conservative for calculating the metal-water reaction rates that would occur in the event of a LOCA.

From the CONCLUSION, page 67:

Petitioner requests that the NRC order the licensee of VYNPS to lower the LBPCT of VYNPS in order to provide a necessary margin of safety—to help prevent a partial or complete meltdown—in the event of a LOCA. Experimental data indicates that VYNPS’s LBPCT of 1960°F does not provide a necessary margin of safety—to help prevent a partial or complete meltdown—in the event of a LOCA. Such data indicates that VYNPS’s LBPCT must be decreased to a temperature lower than 1832°F in order to provide a necessary margin of safety.

NRC Chairman Jaczko, Baker-Just, PRM-50-76

Jaczko visited the Vermont Yankee Nuclear Power Plant and vicinity on or about July 14, 2010. He should have stayed home and tended to business. All this is covered in the following five slides. Click to enlarge and use your back arrow to return for the next slide.





Tuesday, July 6, 2010

Sunday, July 4, 2010

BAKER-JUST and SPARKLERS (Single Rods ain’t Bundles)

I've discussed the 2200 degree Fahrenheit game that NRC plays; a game that is derived from the single rod tests that are referenced by Baker-Just. With bundle tests, runaway starts at much lower temperatures.

Analogies have weaknesses. However, the following from the Wall Street Journal is interesting. A bundle of sparklers yields wild behavior.