Actively cooled first-wall mock-ups have been tested under relevant heat fluxes in electron beam facilities (accelerated fatigue tests) or in low-heat flux facil­ities, which are capable of delivering moderate heat flux (< 1 MW m~2) via electrical heaters for a very large number of heat pulses (>10 000) of larger dura­tion to investigate the thermomechanical performance (including integrity and possible creep phenomena) of the bonded interfaces and fatigue lifetime. Because of intrinsic limitations, cost, or the limited availability of testing facilities, electron beam facilities are used with the shortest duration of the heating cycle, com­patibly with the conditions of near thermal steady — state. In many cases, to reduce the testing time, the tests are performed at a heat flux well above the nomi­nal one. These tests are often used to select the best joining conditions and then confirmation and final selection are done including tests at representative moderate heat fluxes but for the specified large number of cycles. Because of the health hazards linked to the use of beryllium material, only a limited number of test facilities were available or built for testing beryllium components. As far as Be-compatible electron beam facilities are concerned, two are available in Europe, the Juelich divertor test equipments in hot cells (JUDITH 1 and JUDITH 2) at the Forschungszen — trum Juelich (FZJ) (Germany), one in the Russian Federation at the Efremov Institute in St. Petersburg and one in the United States at Sandia National Labo­ratory in Albuquerque (New Mexico). For the perfor­mance of thermal fatigue tests at moderate heat fluxes and large number of cycles, three facilities were built in Europe, one at the Ispra Joint Research Center in Italy, one at the ENEA Research Center of Brasimone in Italy, and one at the Nuclear Research Institute (NRI) of Rez close to Prague in the Czech Republic. From these three facilities, only the last one is still under operation.

The best high heat flux test results from represen­tative first-wall mock-ups, namely, 10-mm beryllium tiles joined onto 10 mm CuCrZr heat sink layer with embedded 10/12 mm diameter stainless steel pipes and the assembly joined onto a stainless steel backing plate (see Figure 11), were achieved with Ti and Cu interlayers and HIP temperatures of about 580 °C as described in Section 4.19.5.1.1.2. The per­formance limit of this assembly is presently at about 3 MW m~2.162

As far as the thermal fatigue tests are concerned, representative first-wall mock-ups with Be/CuCrZr

joints made as above have been successfully tested up to 30 000 cycles at about 0.6 MW m-2 (see Figure 12). Ultrasonic testing of the Be/CuCrZr joints after testing did not show any indication of defects. These mock-ups will be tested at higher heat fluxes representative of transient and off-normal events to check the available performance margins.

Originally, six ITER Domestic Agencies were candidates for the procurement of the ITER first wall: China, European Union (EU), Japan, South Korea, Russian Federation, and United States. (The seven members of the international ITER project have all created Domestic Agencies to act as the liaison between national governments and the ITER Organization. The Domestic Agencies’ role is to han­dle the procurement of each member’s in-kind con­tributions to ITER.) However, as stated in the Final Report of Negotiations on ITER Joint Implementa­tion of 1 April 2006, a prequalification ‘‘… will be needed for the critical procurement packages shared by multiParties…’’, such as the blanket first wall. Well in advance of the assumed start of the procure­ment, each ITER Domestic Agency shall first dem­onstrate its technical capability to carry out the procurement with the required quality, and in an efficient and timely manner. For the first wall system, this is achieved via a two-stage qualification process: a mock-up qualification stage and a semiprototype qualification stage. Each stage is also split into two phases: a manufacturing acceptance phase and a heat flux testing acceptance phase. The successful manufacturing and testing of two first wall mock — ups for stage I (see Figure 13) demonstrating in particular the know-how to assemble beryllium (Be)

tiles on a CuCrZr alloy and stainless steel bimetallic structure is the prerequisite to be eligible for stage II.

The qualification tests for stage I have been split between the United States and EU in three test facilities: at the SNL for the US and at the NRI in the Czech Republic and the FZJ in Germany for the EU. At the SNL facility, the qualification test programme consists of the performance of 12 000 cycles at 0.88 MW m-2 for 1.6 min followed by 1000 cycles at 1.4 MW m-2, while in the EU test facilities it consists of the performance of 12 000 cycles at 0.62 MW m-2 for 5 min (at NRI) followed by 1000 cycles at 1.75 MW m-2 (at FZJ). To be qual­ified, a Domestic Agency shall fabricate two mock — ups which pass both tests.

The first wall mock-ups fabricated by the EU Domestic Agency have successfully achieved the above test programme conditions without any indi­cation offailure. Additional tests were also performed on these mock-ups to assess the limit and tests were performed for 200 cycles at 1.7 MW m-2 at the SNL and for 100 cycles at 2.25 MW m-2 plus 100 cycles at 2.75 MW m-2 at FZJ without any indication of fail­ure. Tests were stopped so as not to exceed the maximum acceptable Be temperature in the test facilities. The progress on the fabrication and thermal tests is described elsewhere.163-171