ML20080B798
| ML20080B798 | |
| Person / Time | |
|---|---|
| Site: | Fort Calhoun  |
| Issue date: | 01/27/1984 |
| From: | William Jones OMAHA PUBLIC POWER DISTRICT |
| To: | John Miller Office of Nuclear Reactor Regulation |
| References | |
| LIC-84-021, LIC-84-21, NUDOCS 8402070276 | |
| Download: ML20080B798 (7) | |
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e Omaha Public Power District 1623 Harney Omaha Nebraska 68102 402/536-4000 January 27, 1984 LIC-84-021 Mr. James R.
Miller, Chief U.
S.
Nuclear Regulatory Commission Of fice of Nuclear Reactor Regulation Divisior. of Licensing Operating Reactors Branch No. 3 Washington, D.C.
20555
Reference:
Docket No. 50-285
Dear Mr. Miller:
License Amendment Application on Reactor Vessel Surveillance Capsules Pursuant to discussions held with Mr.
E.
G.
Tourigny of your staff, the attached information is provided in response to verbal questions asked in regard to the subject license amendment.
Sincerely, NQ- '
W.
C.
Jones Division Manager Produc'tjion Operations WCJ/JJF:jmm Attachment cc:
LeBoeuf, Lamb, Leiby & MacRae 1333 New Hampshire Avenue, N.W.
Washington, D.C.
20036 Mr.
E.
G.
Tourigny, Project Manager Mr.
L.
A.
Yandell, Senior Resident Inspector 8402070276 840127 DR ADOCK 05000285 l
p PDR 45 5124 Employment with Equal Opportunity Male, Female l t
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-NRC QUESTION Provide information on the materials used in making the replacement capsules.
Response
The test material _. for the replacement test specimens was weld metal obtained from the archive block sections (weld metal Block 5 and Block 3 heat-af fected zone).
- Four types of. specimens were selected for encapsulation; they were Charpy V-notch, compound bend, dynamic tension, and compact tension specimens.
The replacement capsules have the same basic configuration as that used for the present capsules. The individual compartment length changed, but the overall length of the assembly remained the same.
Neutron flux monitors were 'provided in four separate compartments over the length of the assembly so that the axial profile could be ovaluated. The attached figure shows the replacement surveillance capsules.
The following is a' brief description of the contents of tha seven capsule compartments of the Fort Calhoun replacement capsule assemblies, a)
Flux and Compound Bend Compartment Each of these compartments was loaded with one set of four flux monitors and two compound bend specimens.
b)
Flux and Compact Tension Compartment Each of these compartments was loaded with one set of five flux monitors and six 1/2t compact tension specimens.
c)
Compound Bend Compartments Each of these compartments was loaded with three compound bend specimens.
d)-
Temperature, Flux, and Tension Compartments Each of these compartments was loaded with two sets of four and five flux monitors, one set of temperature monitors and four dynamic tension specimens.
e)
Charpy Capsule Compartments Each of these compartments was loaded with 12 Charpy impact specimens in a 3 x 4 x 1 array with the notch toward the core.
. Neutron flux monitors are provided in four separate compartments in each capsule so that the axial flux profile can be determined. The types of flux monitors to be used are listed in Table 1; they were selected to provide threshold detectors over a broad range of neutron energies (thermal plus 0.5 to 15 MeV). These detectors possess reasonably long half-lives and activation cross-sections to monitor the thermal and fast neutron spectra incident on the test specimens.
TABLE 1 MATERIAL FOR NEUTRON FLUX MONITORS Threshold Material Reaction Energy (MeV)
Half-Life Uranium
NiS8(n,p)CoS8 5.0 71 days Copper **
Cu63(n,a)Co60 7.0 5.3 years Titanium Ti46(n,p)Sc46 8.0 84 days Cobalt
- CoS9(n,Y)Co60 Thermal 5.3 years Neptunium **
Np237(n,f)Cs137 0.5 30.2 years
- Cadmium shielded Changes in the material properties of the irradiated specimens are dependent on the temperature during exposure in the reactor vessel.
The maximum temperature during irradiation is estimated with reason-able accuracy by including one set of four temperature monitors in each capsule assembly. The temperature monitors consist of a helix of low melting alloy wire inside a sealed quartz tube. A stainless steel weight is providcd to destroy the integrity of the wire when the melting point of the alloy is reached. The compositions and therefore the melting temperatures of the temperature monitors (Table 2) are differentiated by the physical lengths of the quartz tubes which contain the alloy wire.
TABLE 2 COMPOSITION AND MELTING P0INTS FOR TEMPERATURE MONITOR MATERIALS Composition Melting Temperature Wt%)
('F) 80.0 Au, 20.0 Sn 536 90.0 Pb, 5.0 Sn, 5.0 Ag 558
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97.5 Pb, 2.5 Ag 580 97.5 Pb, 0.75 Sn, 1.75 Ag 590 The replacement capsule installed at the 265 location is scheduled to be withdrawn between 10 and 14 EFPY following plant startup. The replacement capsule installed at the 225' location is scheduled to be withdrawn between 20 and 24 EFPY following plant startup.
The withdrawal schedule for the six original capsules was designed to meet the requirements of 10 CFR 50, Appendix H, " Reactor Vessel Material Surveillance Program Requirements." The replacement capsules are intended to provide supplemental fracture toughness properties and neutron dosimetry data for the Fort Calhoun reactor vessel. The removal schedule for the two replacement capsules was designed to obtain an exposure equiYalent to 25-50% of the end-of-life fluence at the inside surface of the reactor vessel for the first capsule, and approximately 75% for the second capsule. The timing of the withdrawal may be modified if the specific needs for fracture toughness and dosimetry data change at a later date.
Furthermore, adjustments to the schedule may be required because the neutron flux on the replacement capsule could change with modifica-tions to fuel management techniques.
The District recommends that the new capsules be designated " Replace-ment" capsules and that Table 3-7 of our submittal be changed to the followi ng.
TABLE 3-7 CAPSULE REMOVAL SCHEDULE Removal Refueling Schedule Capsule Schedule EFPY Removed 1
2.6 225*
2 5.9 265*
3 10 45*
4 Replacement
- 225**
5 17 85*, 95*, 275*
6 24 85*, 95*, 275 7
Replacement
- 265**
8 Standby Any Remaining Capsule 1
The alternative capsule for removal should be determined prior to attempting removal of any scheduled capsule.
- Replacement capsule assemblies were installed in the 225* and 265 locations after early withdrawal of the original 265* capsule.
These capsules will benchmark the change in core loading design initiated at 5.9 EFPY and will provide supplemental fracture toughness properties data for the Fort Calhoun reactor vessel.
NRC QUESTION What are the accumulated fluences for capsules 3, 4, and 5 at the scheduled time of removal?
Response
The accumulated fluences are given in the following table.
Old Anticipated
- Removal Removal Accumulated Sequence Location Time (EFPY)
Fluence (n/cm21 3
45*
10 2.4
- 1019 4
85*, 95 or 275*
17 2.6
- 1019 5
85*, 95* or 275*
24 3.7
- 1019
- Based on a linear extrapolation of the E0C 7 fluence assuming no credit for reduced radial leakage reload cores.
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_ NRC QUESTION What are the lead factors for all capsule locations?
Response
The lead factors are given in the following table. The lead factors assume no change in fuel loading schemes from that employed in Cycles 1 through 7.
Lead Factor Lead Factor Lot?tions Vessel / Clad Interface 1/4 Thru Vessel 45' and 225*
1.57 2.61 85*, 95*, 265*, 4 276 1.02 1.70 NRC QUESTION What is the projected end-of-life fluence of the vessel?
Response
The following table provides the projected end-of-life fluence assuming a linear extrapolation of the end-of-cycle 7 fluence and taking no credit for reduced radial leakage reload cores.
Fluence BOL-E0L Location (n/cm2)
Vessel / Clad Interface 4.8
- 1019 1/4 Thru Vessel 2.9
- 1019 1/2 Thru Vessel 1.4
- 1019 3/4 Thru Vessel 8.0
- 1018 l
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Lock Assembly g
Wedge Coup'ing Assembly
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Extension Assembly 1'
(i) Flux & Compound bend Capsule Assembly
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@ Flux & 1/2t Compact Tension Capsule Assembly
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@ Assembly Compound Bend Capsule s 7
@ Temp.le Assembly Flux & Tension Capsu s-
@ Assembly Compound Bend Capsule
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@ Flux & 1/2t Compact Tension Capsule Assembly
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5; REPLACEMENT SURVEILLANCE CAPSULE ASSEMBLY FOR FORT CALHOUN REACTOR
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