Patent ID: 8106362

Claim:
A surface contamination examining device comprising: (a) a radiation detector that detects radiation; and (b) an arithmetic/display device that processes an output pulse from the radiation detector and displays radiation intensity in the form of a counting rate, (c) wherein the arithmetic/display device has a boundary detecting device that detects the boundary of contamination of an object to be measured by a radioactive material when the radiation detector moves along a surface of the object to be measured at a substantially constant speed; (d) wherein the boundary detecting device comprises (i) a counting rate storage unit containing instructions to sequentially store the counting rate Y i at a predetermined time interval, wherein i is an integer of 1 or larger; (ii) a slope arithmetic unit containing instructions to compute slopes a M and a N of approximation lines from M counting rates Y i in a predetermined range and N counting rates Y i from among the M counting rates Y i , wherein M is an integer of 3 or larger and N is an integer smaller than M; and (iii) a boundary determining unit containing instructions to compare the slopes a M and a N to determine the boundary of contamination of the object to be measured by the radioactive material.