Environmental Engineering Reference
In-Depth Information
UONI 13/55
EA-898
ZIO-8
5.15 Assembly weld No. 1 (cross section). 
electrodes UONI 13/55 with the transition layer welded with electrodes
ZIO-8 and EA 898 (cladding layer).
The welded joint was described by a confirmed certificate showing the
coordinates, size and type of defects. Due to confidentiality of the data
for the coordinates of the location of the defects each defect was assigned
a number.
Manual ultrasonic testing was carried out as 'a blind' test, i.e., NDT
inspectors were not aware of the number and coordinates of the location of
defects. Serial flaw detectors UD2-12 and UDTs-107 were used, together
with Priz transducers with the entry angles of 0, 50 and 65 o . Sensitivity
was adjusted using the SO-2 reference sample in accordance with GOST
14782-86. Regular NDT inspectors of four nuclear power plants with RBMK
reactors carried our inspection.
Automatic ultrasonic testing was performed as 'a blind' test using
Tomoscan equipment, followed by data analysis and comparison of reports
at the TomoLuis workstation (development of the Swedish company TRC).
The transverse welded joint was inspected by the non-parallel TOFD-
method with scanning in the clockwise direction. Focusing was carried
out on 2/3 of wall thickness. Additionally, to cover the entire volume of
the welded joint, the echo-pulse method on longitudinal (45 and 60 o ) and
transverse (45 and 60 o ) waves was used.
Radiographic inspection of the sample was carried out in three directions
to the normal of the weld 0, +13 and -13 o (Fig. 5.16).
A defect was regarded as detected if the coordinate X f , mm, recorded in
the report, corresponded to the interval
￿ ￿ ￿ ￿ ￿
X m - ( a m /2) - ∆ X m < X f < X m + ( a m /2) + ∆ X m ,
where X m is the mean detection coordinate according to the certificate;
a m /2 is the average length of the defect according to the certificate; ∆ X m is
the confidence interval of location X m of the defect on the certificate.
The inspection results indicate that most discontinuities were detected
 
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