Patent Number: 
Section: claims

1. A method of irradiating multiple specimens within a core (14) of a nuclear reactor (16) that has a moveable in-core, radiation detector flux mapping system, wherein the core comprises a plurality of fuel assemblies respectively having instrument thimbles into which a radiation detector (12) of the flux mapping system can be inserted and travel through, comprising the steps of:inserting a first specimen holder (48) containing a first specimen (72) at a lead end of a first drive cable (36) driven by a first drive unit (34), into a first instrument thimble in the core (14);remotely detaching the first drive cable (36) from the first specimen holder (48) and fixing an axial position of the first specimen holder within the first instrument thimble;withdrawing the first drive cable (36) from the reactor (16);attaching a second specimen holder (48) containing a second specimen (72) to the lead end of the first drive cable (36) driven by the first drive unit (34);inserting the second specimen holder (48) containing the second specimen (72) into a second instrument thimble in the core (14);remotely detaching the first drive cable (36) from the second specimen holder (48) and fixing an axial position of the second specimen holder within the second instrument thimble;withdrawing the first drive cable (36) from the reactor (16);in between the withdrawing step and the second inserting step inserting a moveable in-core radiation detector (12) from the moveable in-core detector radiation flux mapping system, attached to a second drive cable (50) driven by a second drive unit (24), into and through a third instrument thimble; andwithdrawing the moveable in-core radiation detector (12) from the reactor (16) after performing a flux mapping exercise. 2. The method of claim 1 wherein the inserting steps insert specimen holders (48) into as many as half the instrument thimbles accessible by the flux mapping system for simultaneous irradiation at a time when a flux map is to be conducted. 3. The method of claim 1 wherein the steps of fixing the axial position of the specimen holders (48) within the respective instrument thimbles includes the steps of determining when the respective specimen holders are at a preselected axial position within the corresponding instrument thimbles. 4. The method of claim 1 wherein the step of withdrawing the first drive cable (36) from the reactor comprises withdrawing the first drive cable out of the moveable in-core, radiation detector flux mapping system prior to the running of a flux map.