Radiation embrittlement

In calculating the system and barrier failures, consideration should be given to radiation embrittlement, chemical reactions, thermal shock, and metal fatigue. 

Popp, K., Brauer, G., and Leonhardt, W.-D. et al., (1989) in Radiation Embrittlement of Nuclear Reactor Pressure Vessel Steels An International Review, ASTMSTP1011, ed. By L.E. Steele (American Society fro Testing and Materials, Philadelphia)... 

Low pressure in the primary circuit enables to reduce the thickness of reactor vessel walls and to use for its fabricating less strong austenite steel being resistant to radiation embrittlement under operation conditions and eliminate the possibility of vessel brittle damage. This enhances safety and eliminates the restrictions on temperature change rate on conditions of thermocycling strength and radiation life time of reactor vessel. 

AR378 1.99 Radiation embrittlement of reactor vessel materials (Draft ME 305-4, Proposed revision 2,... 

The cost, allowable time of operation, and possibility of inexpensive disposal are the main consumer features of RCCA. In order to increase RCCA lifetime it is required to replace the bottom (300-500 mm) n/a absorber B4C by unswelling n/y absorber (Hf, Dy2Ti05 or In + Cd + Ag) and to use cladding material that will be more stable against radiation embrittlement (according to the researches, as the calculation data of the thermal neutrons flux density above reactor core has appeared to be below actual). 

Adequate operational procedures may also contribute to reducing the probability of generating a PIE. Examples include the prevention of excessive thermal stresses in metal pressure vessels and the monitoring of vessel material for radiation embrittlement the limitation of plant transients by the use of pressure relief valves and safety features activated by the protection system prohibitions or restrictions during the conduct of dangerous operations the use of seismic instruments to provide data for the assessment of the condition of the plant for continued operation following an earthquake and the control of... 

Key words pressurized water reactor (PWR), reactor pressure vessel (RPV), surveillance database, radiation embrittlement. 

The effect of neutron fluence on radiation embrittlement has been reported to be signiflcant at fluences above 10 n/cm ( > IMeV). An increase in neutron fluence results in an increase in RTndt, yield strength and hardness, and a decrease in upper-shelf toughness. 

The latest version, PR-EDB Version 3, contains test results of 104 HAZ materials, 115 weld materials and 141 base materials, including 103 plates, 35 forgings and three correlation monitor materials that were irradiated in 321 capsules from 106 commercial power reactors. It was a Windows PC-based program (Windows 98 through XP only) using data files in MS Access format. It is being replaced by the Radiation Embrittlement Archive Project (REAP) (Klasky et al., 2013). 

Radiation embrittlement of US RPVs is currently evaluated according to the guidance of Regulatory Guide 1.99, Revision 2, and the embrittlement correlation which is implicit in that guidance (Randall, 1986). In the... 

The US NRC is currently engaged in an effort to develop a modern, web-based embrittlement database named the Radiation Embrittlement Archive Project (REAP) (Klasky et al, 2013). The objective is to address previous database sustainability issues (e.g., the challenge of keeping data retrievable... 

Klasky H, Williams P and Bass B (2013), Radiation Embrittlement Archive Project Web Application User s Guide , ORNL/TM-2013/45083, Oak Ridge National Laboratory, Oak Ridge, TN. 

NRC 19 ), Regulatory Guide 1.99 Revision 2, Radiation Embrittlement of Reactor Vessel Materials, May, Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, Washington, DC. 

Randall P (1986), Basis for Revision 2 of the US Nuclear Regulatory Commission s Regulatory Guide 1.99, Radiation Embrittlement in Nuclear Pressure Vessel Steels An International Review (2nd Volume),STP 909, Steele LE (ed.), American Society for Testing and Materials, Philadelphia, PA, pp. 149-162. 

Tomimatsu M, Asada S, Namatame H, Ohtani M and Watada M (1996), Evaluation of RPV steel surveillance program in Japanese PWR radiation embrittlement, prediction . Proceedings of P" International Symposium on REACTOR DOSIMETRY,Ahde m] m H A, O Hondt P and Osmera B (eds), Prague, Czech Republic, 2-6 September, 1996, World Scientific, Singapore. 

Abstract This chapter describes the embrittlement processes in WWER reactor pressure vessel (RPV) materials during operation - radiation embrittlement and thermal ageing. Current trend curves for both types of WWER RPV materials are given and explained. Surveillance specimen programmes are shown, as their results are used for RPV integrity and lifetime evaluation. Finally, anneahng of the RPV is proposed as the most efficient mitigation measure. 

Key words WWER reactor pressure vessel, radiation embrittlement,... 

The beltUne regions of the WWER-440A -213 (i.e. second generation) pressure vessels were also manufactured from 15Kh2MFAA steel, but most of the V-213 pressure vessels have low phosphorus and copper contents and are similar in impurity content to the WWER-1000 pressure vessels with strict requirements on the residual element (copper, phosphorus, arsenic, tin and antimony) content, i.e. their steel and welds are of 15Kh2NMFAA quality. Thus, radiation embrittlement does not seem to be a limiting factor... 

For calculation of 50 % (median) curves of AT i(F, t) according to Eq. 5.5, the value a = 0 should be taken, both for base and weld metal. This type of dependence is used for direct determination of radiation embrittlement parameters based on results of RPV-specilic surveillance specimen tests. Typical trend curves calculated according to the Eq. 5.4 for base metal and weld metal are shown in Figs 5.2 and 5.3. It can be seen that mean curves provide a good description of the distribution of test results from surveillance specimen programmes. 

Irradiation embrittlement in RPVs mainly results in two consequences. First, it narrows the pressure-temperature operation window for normal operating conditions. Second, it limits RPV lifetime as the transition temperature of RPV materials cannot be higher than that determined from the pressurized thermal shock (PTS) calculations. Several mitigation measures can be applied to decrease radiation embrittlement of RPV beltline materials ... 

Regarding the neutron fluence value at the time of annealing, no substantial effects were found. Residual embrittlement, as well as the rate of further re-embrittlement, is practically independent of this neutron fluence. The lateral (horizontal) shift approach was also confirmed in the IAEA Round Robin Exercise on radiation embrittlement of WWER-440 weld metal, as shown in Rg. 5.16. The microstructure investigation results demonstrate that copper clusters, which are formed in material under primary irradiation, are not recovered during annealing to a structure of solid solution such as that in the unirradiated state. 

Key words radiation embrittlement, pressnrized thermal shock, fractnre toughness, pressnre-temperatnre limit curves, structural integrity. 

In Japan, the approach is again very similar to the US method (JSME, 2009). The definition of RTVidt is the same as in the ASME Code. ARTndt = AT41J for radiation embrittlement is used where the CVN test generally follows the ASTM standard for PWRs (ASTM, 2007a) and the ISO standard (ISO, 2009) for BWRs. 

The approach for German vessels is again essentially the same as the US method using initial RT m and ARTndt = AT4U for radiation embrittlement. German standards are used as defined in the recently revised KTA 3203 (KTA, 2001). The ISO tup is used for Charpy tests, like the French method. The use of RTt as defined in the ASME Code Cases is allowed in KTA 3203. 

In order to open the operating window for P-T curves and allow for a widened margin against PTS, mitigative measures may be applicable to reduce the impact of radiation embrittlement. These mitigative methods include ... 

R B Jones and C J Bolton, Neutron radiation embrittlement studies in support of continued operation and validation by sampling of Magnox reactor steel pressure vessels and components, Proc. 24 Water Reactor Safety Information Meeting, NUREG/CP-0157, US Nuclear Regulatory Commission, Washington, DC, 1997, 2,25-48. 

Abstract This chapter discusses the role of simulation irradiation techniques in studies of radiation embrittlement mechanisms. The chapter first reviews characteristics and examples of test reactor irradiation, ion irradiation and electron irradiation. The chapter then discusses advantages and limitations of these techniques from the viewpoint of damage rate, sample volume and damage characteristics. 

It is widely known that radiation embrittlement behaviour of reactor pressure vessel (RPV) steels depends on various parameters such as material composition, neutron flux and irradiation temperature. Sound understanding and modelling of embrittlement mechanisms require systematic knowledge of effects of individual parameters and their synthesis on microstructural development and then mechanical properties. Most such knowledge has been obtained from single-parameter experiments using test reactor irradiation. This is because test reactor irradiation allows researchers to obtain mechanical property data together with microstructural data on materials with well-controlled chemical compositions under well-controlled irradiation conditions such as flux and temperature. Surveillance data in commercial power reactors are non-systematic in this context and relevant microstructural data are very scarce. 

Test reactor irradiation has been widely used for studies of radiation embrittlement in RPV steels and huge amounts of data and reports are... 

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