ML20104A371
| ML20104A371 | |
| Person / Time | |
|---|---|
| Site: | Fort Calhoun  |
| Issue date: | 02/15/1979 |
| From: | OMAHA PUBLIC POWER DISTRICT |
| To: | |
| Shared Package | |
| ML20104A348 | List: |
| References | |
| NUDOCS 7903130363 | |
| Download: ML20104A371 (7) | |
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FORT CALHOUN STATION CYCLE IV IRRADIATED FUEL INSPECTION
,FOLLOWING, CYCLE IV OPERATION November - Ddcember 1978 w v..
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February 15, 1979 I
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e A visualinspection of 52 irradiated fuel assemblics was performed.
The visual inspections included eight (8) assemblics which were reloaded for Cycle 5 operation. The remaining 44 visually inspected bundles were not returned to the core for Cycle 5.
Eddy current testing was performed on ten (10) fuel assemblies. Seven (7) of the assemblies subjected to cddy current testing were returned to the core for Cycle 5.
The visualirispections were performed in accordance with SP-FE-1.
' A list of the visually inspected. assemblies is found in Table 1.
The inspections were performed using the spent fuel inspection stand, an underwater closed circuit television system, the spent fuel handling mach-ine (FH-12), and associated lighting equipment. The television system included a camera equipped with a 5:1 zoom lens, a video tape recording device, and a monitoring unit. When inspecting assembly B009, a fixed
. lens underwater television camera was used. Inspection of the remaining assemblies was accomplished using the zoom lens equipped camera.
.Visualinspection was accomp}ished by inserting the inspected assembly inside the inspection stand, :using the spent fuel handling machine. Once
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the assembly is inside the irispection' stand, ;it can be viewed wie Ge tele-vision camera..By moving the assembly in the vertical dirmion with the refueling machine, the entire length of the assembly can be observed.
A minimum full-face scan was obser"ed and recorded on video tape for all faces of each assembly. The f 21'pce scan vias accomplished at low
' magnification.. Additional inspections at higher magnifications were per-formed as required following observation of any apparent abnormality
.during the full-face scan. The camera mount on the inspection stand per-imitted complete lateral coverage of the entire assembly face at any mag-nification. All four faces of the inspected assembly were observed by successive withdrawal and rotation of the assembly.
It should be noted that the pool-side television monitor has been mod-ified to eliminate mirror-imaging which results from the use of a right' angle mirror on the camera. The virbo tapes, however, record a mir-ror image, i.e., images appearing on the right really represent the left side of the object. The auto dubbing comment may refer to the right side C!
of the assembly face but, when the video tape is viewed on a monitor with-out the mirror-image eliminator, the right side will appear on the 1 cit.
The notation used to indicate the identity of the face being examined is defined by calling the face which faces the north direction when the assem-bly is in the southeast orientation as the north face. Figure 1 shows the assembly mapping scheme.
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A December 15, 1978 Page Two No abnormalitics were observed in the eight (8) assemblics returned to the core. ' Some oxide formations were apparent, but these were nor-mal. Of the 44 discharged assemblies inspected, only two (2) assemblics exhibited abnormal mechanical conditions. Assembly D012 had what appeared to be corrosion on the fifth spacer grid from the bottom of the east face. The damage appeared as a hole in the grid face adjacent to pin M-14 (Figure 1). The damage did not appear to have resulted from fuel handling. Assembly D022 exhibited a failed pin in location N-2 (Fig-ure 1). Two (2) holes wer~e apparent in the cladding: one between the fourth and fifth grid from the bottom and the other between the fifth and sixth grid from the bottom. These holes appeared to be in an advanced stage of hydriding. A possible third hole existed between the above two holes. The holes appeared to be the result of corrosion rather than mech-anien1 damage. However, it is possibic that the corrosion could have initiated, by manufacturing defect, by pellet clad interaction, or follow-ing mechanical damage. The above pin showed additional evidence of surface corrosion in the vicinity of the holes. Pins on both sides' of the.
failed pin did nct exhibit-any abnormalities.
Out of the 2704 pins observed duri$g visual examination of 52 assem-blies, only one (1) pin was found to exhibit appreciable clad damage.
This is less than.04% observable pin failures among the pins inspected.
The low radioactivity levels of the reactor' coolant during Cycle 4 opera -
tions indicated good fuel integrity. Visual examination of the facial pins
'(which comprise ap' proximately 30% of all the pins in an assembly) con-firmed, by discovery of only one (1) failed pin, the excellent fuel integ-rity maintained during Cycle 4 operations. The above abnormalities are minor in nature and are not expected to impact Cycle.5 operations.
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In addition to the visual inspections eddy current testing (ECT) was, performed on ten (10) "D" assemblies. These assemblies were selec-ted because they contained CEAs during Cycle 4 andbecause they occu-pied core locations near the hot legs. Experience uith other Combus-tiori Engineering (CE) assemblies suggcets that guide tube wear is most likely to be found in these locations. Assemblies which were tested using the eddy current method are listed in Table 2. The eddy current testing was completed using Special Procedure SP-FE-8 to verify that no appreciable guide tube wear had occurred in the newer reconstitut-able type fuel assemblics. Eddy current testing had previously been performed on Fort Calhoun non-reconstitutable fuel, and no significant wear had been observed. However, both CE and NRC interest promp-ted the further testing of the newer (mechanically different) type fuel to check for guide wear problems. The tests were performed in the spent fuel pool by lowering a one-inch diameter ECT probe (on approx-imately 40 feet of steinicss steel tubing) into each fuel assembly guide
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Page Three tube using the spent fuel handling machine. As the probe was withdrawn from the guide tube, the voltage and conductivity of the bobbin coil, which was mounted inside the probe, were monitored. The absence of a signal voltage means no wear has occurred in the guide tube. The bobbin coil voltage and conductivity were monitored and recorded for each guide tube d'
of the ten (10) inspected assemblics. The only assembly exhibiting any appreciable voltage signal was D002. The NE guide tube had a voltage
- reading of 1. 0 volt. A voltage reading of 1.0 volts corresponds to no
- appreciable guide tube wear. No other assemblics had voltage readings above 0. 5 volts. Based on the eddy current testing, it can be concluded that no significant guide tube wear problem exists in the CE supplied Feet Calhoun fuel assemblics.
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Tabic 1 List of Irradiated Fuci Assemblies Inspected Visually 1.
A004 18.
C001 35 D016 2.
A012 19 c010 36.
D017 3
A013 20.
Coll 37 D018 h.
A015 21.
C013 38.
D019 5
A019 22.
D001 39 D020 6.
A021 23 D002 ho.
D021 7
A025 24.
D003 hl.
D022 8.
A027 25 D004 h2.
D023 9
A028 26.
D005*
43 D02h 10.
A029 27 D007 hh.
D025 11.
A030 28.
D008 45 D026 12.
A032 29 D010 46.
D033*
13 A033 30.
D011 h7 D034*
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A035 31.
D012
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15 A0kk 32.
D013 h9 D044*
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A045 33.
D01h 50.
F00h*
17 B009 34.
D015 51.
E001*
52.
E101*
- Returned to core for Cycle 5 irradiation.
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Table 2 Lict of. Irradiated Fuel Assemblies Inspected by Eddy Current Testing 1.
D002 2.
D003 3
D00k 4
D006*
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D009*
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D01h 7.-
D019 8.
D020 9
D02k 10.
D0hl*~
- Returned to core for Cycle 5 irradiation.
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12/15/78 FIGURE 1 5
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