Measuring and testing – Embrittlement or erosion
Patent
1996-12-17
1998-09-15
Noland, Thomas P.
Measuring and testing
Embrittlement or erosion
73 87, 374 53, G01N 1700, G01N 2502, G01N 3320
Patent
active
058081836
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATION
This application is a national stage of PCT/DE95/00736 filed 30 May 1995 published as WO95/35499 Dec. 28, 1995 and based upon German national application P44 21 009.4 of Jun. 20, 1994 under the International Convention
FIELD OF THE INVENTION
The invention relates to a method for calculating the transition temperature curve of irradiated low-alloy reactor pressure vessel steel for the irradiation temperature range of 250.degree.-320.degree. C.
BACKGROUND OF THE INVENTION
In order to evaluate the brittle fracture safety of safety-relevant components in reactor technology, knowledge of the change in mechanical properties as a function of neutron flux is required. In current practice, test specimens are irradiated in the nuclear reactor and removed and examined at defined time intervals. The condition of a component of the same material in the reactor is inferred from these results. An additional safety-related calculation of embrittlement is performed using the US-NRC rules Reg.Guide 1.99 ff and the German KTA rules based thereon. Copper and nickel contents of the steel must be known for the application of these rules.
OBJECT OF THE INVENTION
It is the object of the invention to calculate the embrittlement of a reactor pressure vessel in operation.
SUMMARY OF THE INVENTION
This object is achieved according to the invention by a procedure wherein the transition temperature curve of irradiated low-alloy reactor pressure vessel steel for the irradiation temperature range of 250.degree. to 320.degree. C. is calculated in that the instrumented Charpy impact test is carried out with unirradiated material specimens of the pressure vessel steel determining transition temperature curves for the partial energy values Ea, Eb and Ec. The hydrogen concentration K.sub.H2 (specified in ppm) of the unirradiated material specimens of the steel, the oxygen concentration K.sub.O2 (specified in ppm) of the unirradiated material specimens of the steel and their metallographic microstructure are determined. The energy decrease .DELTA.Ea for the case of saturation irradiation is determined according to the relation determined according to the relation
The increase in transition temperature for the transition temperature curves of the partial energy values Ea, Eb and Ec for the case of saturation irradiation is determined according to the relation
The values determined for .DELTA.Ea and .DELTA.TT are used to determine the transition temperature curve for the partial energy Ea for the case of a material specimen irradiated up to saturation, the values determined for .DELTA.Eb and .DELTA.TT are used to determine the transition temperature curve for the partial energy Eb for the case of a material specimen irradiated up to saturation, and the values determined for .DELTA.TT are used to determine the transition temperature curve for the partial energy Ec for the case of a specimen irradiated in saturation.
The transition temperature curves thus determined for the partial energies are then superimposed to determine the transition temperature curve for the pressure vessel steel for the case of saturation irradiation, with
The transition temperature increase for preselected energy values can be determined by comparing the calculated transition temperature curve for the irradiated pressure vessel steel with the transition temperature curve determined by Charpy impact tests of unirradiated material specimens.
BRIEF DESCRIPTION OF THE DRAWING
The above and other objects, features, and advantages will become more readily apparent from the following description, reference being made to the accompanying drawing in which:
FIG. 1 is a graph of impact energy vs temperature illustrating the invention; and
FIG. 2 is a graph of load vs time.
SPECIFIC DESCRIPTION
In the following, the method will be described by which the change in mechanical characteristics due to reactor irradiation is calculated from gas analyses and microstructural investigations of unirradiated specimens.
Calculations are p
REFERENCES:
Patent Abstracts of Japan vol. 12, No. 161, (P-702), Ab. Date May 17, 1988 (62-274258) "Method for Evaluating and Testing Characteristic to Stop Brittle Crack Propagation".
Patent Abstracts of Japan vol. 8, No. 163, (P-290) Ab Date Jul. 27, 1984 (59-60347) "Method for Evaluating Deteriotion Degree of Low-Alloy Heat-Resistant Steel".
Dubno Herbert
Noland Thomas P.
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