Review of recent irradiation creep results

Materials deform faster under stress in the presence of irradiation by a process known as irradiation creep.This phenomenon is important to reactor design and has been the subject of a large number of experimental and theoretical investigations.The purpose of this work is to review the recent experimental results to obtain a summary of these results and to determine those research areas that require additional information.The investigations have been classified into four subgroups based on the different experi mental methods used.These four are: (1) irradiation creep using stress relaxation methods, (2) creep measurements using pressurized tubes, (3) Irradiation creep from constant applied load, and (4) irradiation ciecp experiments using accelerated particles.The similarity and the differences of the results from these rThods are discussed and a sum" mary of important results and suggested areas for research is presented, tn brief, the I=?nrtant results relate to th« dependence of creep on swelling, temperature, str>s* state and alloying additions.In each oi these areas new results have been presented and new questions have arisen which require further research to answer.In 19"?, ileske'h 1 published a broad view of the early irradiation creep rest;jr.&<He -included data describing stress, temperature, and Huence dependencies for a broad range of cubic, noncublc, fissile, and no*fissile aa erials.In addition, he reviewed the theoretical explanation off--i a at that tiae.There have been a number of aore recent reviews &..d I call your attention to three of these.Glttus includeJ a lo'nr cnapter on irradiation creep in his book.This aacetlal includes a discussion of the theoretical aodels available at that tine.'r,1977, Straalsund^ collected the available data ne;:sured for irradiation creep in stainless steels, the aaterial cho sen to be the structural aaterial for breeder reactors.Finally, I refer you tt ti.t.review of irradiation creep published by Harries in 1977.In Mils uaper the various aethods for Measuring irradiation creep are described along with a discussion of the advantages and disadvantages of each.Also Harries has related the experiaental measuressr.rsro theoretical explanations in an atteapt to provide sup port for ov t.: discredit each of the models.He also presented a list of sugg ated experiments to answer soae of the reaaining unanswered questienr.The measurement of irradiation creep has not been easy.At tem perature -md .stresseswhere theraal creep rates are very low and irradiation creep can be measured independently, the irradiation creep ratt* *rt Tow and difficult to aeasu.'e.The radiation environaent requlr.dfor the study is a very hostile environaent for materials; and, %"-a result, it is difficult to design testing machines which will co-si-te reliably and accurately enough to make the measurements.As a '.esu't of these difficulties, there have been a wide variety of experiment tl techniques developed to measure irradiation creep.Each of the»f lias its own advantages and disadvantages, and each has pro vide" -isefjl information.A difficulty develops, however, when result.; from one technique are compared with results measured using another technique.In some cases these comparisons can be made on leajonable theoretical grounds while in others no direct comparison is possible.