EXAMINATION OF MATERIAL PERFORMANCE OF W EXPOSED TO HIGH HEAT LOAD - POSTMORTEM ANALYSIS OF W EXPOSED TO TEXTOR PLASMA AND E-BEAM TEST STAND

TANABE T PHILIPPS V NAKAMURA K FUJINE M UEDA Y WADA M SCHWEER B POSPIESZCZYK A UNTERBERG B

T. Tanabe et al., EXAMINATION OF MATERIAL PERFORMANCE OF W EXPOSED TO HIGH HEAT LOAD - POSTMORTEM ANALYSIS OF W EXPOSED TO TEXTOR PLASMA AND E-BEAM TEST STAND, Journal of nuclear materials, 241, 1997, pp. 1164-1169

11

INGLESE

Article

Nuclear Sciences & Tecnology","Mining & Mineral Processing","Material Science

Journal of nuclear materials → ACNP

0022-3115

241

1997

1164 - 1169

ISI

0022-3115(1997)241:<1164:EOMPOW>2.0.ZU;2-F

We have examined the behavior of high Z limiters exposed to TEXTOR edg e plasma and found that under certain conditions high Z materials are compatible with plasmas. In high density Ohmic plasmas the accumulatio n of a high Z impurity in the plasma center with significant radiation is observed, whereas an auxiliary heating like NBI and ICRH enhances the impurity exhaust with saw tooth activity. For a practical use of h igh Z plasma facing materials, extremely high heat load from the plasm a becomes a serious concern. In the present work we have conducted the high heat load tests of tungsten (W) using two different heat sources , one is the W limiter exposed to TEXTOR plasma and tile other is vari ous W samples heat loaded with an intense E-beam using the JEBIS facil ity in Japan Atomic Energy Research Institute (JAERI). From the test r esults we have to conclude that W, if applied in the form of the bulk material, should be used above the ductile brittle transition temperat ure (DBTT) but below about 1500 degrees C to avoid the recrystallizati on. Maximum heat load tolerable without surface melting is about 20 MW /m(2) for several seconds, The monocrystalline used at high temperatur es shows very good performance, though the production of the monocryst alline with a desired shape is not easy, Considering its brittle natur e, hard machining and heavy mass, bulk W cannot be a structure materia l but be used as a thin tile or deposited film on some structure mater ials. Unfortunately, however, the thermal expansion coefficient of W i s so small that brazing of W to a heat sink material like Cu which has a much larger thermal expansion coefficient would easily result in cr acking due to the large thermal stress. Thus the development of tungst en plasma facing component (PFC) needs much effort in future.