ML20024B023
| ML20024B023 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 11/04/1966 |
| From: | Couchman D, Pickard J METROPOLITAN EDISON CO. |
| To: | METROPOLITAN EDISON CO. |
| References | |
| TASK-*, TASK-GB GPU-0182, GPU-182, NUDOCS 8307020041 | |
| Download: ML20024B023 (9) | |
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1 NOTES ON METOC::: LIT.'.H 3DIiCM MSET' KG with -
Bl.ECOC'. *.: WILCOZ I
on Cctober 27, 1963 s
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p225ENT:
F..
K. Davis U"sU - Nuc. Vessels Fuci Elements
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John Ficor 7uel E:ndling R. J. Cuffia L. M. Favret i !!
Nuc. Proposals (part ti:.13)
G. L. Taite
?'il Mgr. Phila. Sales (part t3 Core Design i
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Mol Sankovich Phile. Eslos F. C. Hellcr-I
..t R. E..Neidig
.?, j Mst. Ed. (part ti=e)
J. G. Miller d
- p. p. Xarish G. F. Bie: man E !!
1 GAI (part time)
Geo. W. Switzer
'l D. L. Couchmen
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RUS Corp.
J. K. Pickard
,i pickard, Lowe a Assoc. (part t!h t
W. 3. Layman
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2.
7U2L ECD DESIGN The design of the fuel rods was discussed including center 11nc
- e=perature, fission gas releauc from fuel, end plent st=c, pelict swciling and cladding strain limitations, and the, proportics of the 357 siiated that the 2 2num at the end of the fuel rod 1
cladding.
was slightly over S inches in langth,,or about 25 of the red volume.
The design of the fuel ro1 is based oc a curve giving fission gas release fr ction as a function of fuci te=perature.
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For the peak rod in the core the integrated rc1 case fraction is about 40%.
This relenc.: rate together with the plenum volume i
.j results in a peak internal pressure in the fuel rod of about 3300 psi nt the end-of-lifetir.e, or about 1100 psi above system operating pressure.
Under thase conditions, the cladding has a 9,000 psi tensile stress.
Imnediately after shutdown the clad, ding stress. is about 4,000 ' psi.'.n compression.
After cooldown the cladding stress is about 3,000 psi in tension.
The calculated minimum yield of the cladd:'.ng material is 52,000 psi at the end of coro lif,c.
Mr. Layman n'shed if it wasn't customary to design to a clad peak internal pressure not to exceed coolant operating s
pressure.
e The limiting design criteria for pellet swelling is a m'aximum of 1% cladding strain.
BU3 stated that the 1% limit was believed to be a reasonable and. conservative number but that the available data is too limited to provide a quantitativo justification for a cladding strain criteria (Because of the limited and preliminary nature of the data this value'was questione'd as being less conser-vative tha'n other designs).
The c'alculated pellet swelling.is based primalily on data from published LSER reports.
The fuei centerline temperature calculation is based on UO conductivity 2
data in the published literature although the E23 curve is
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slightly different from that,used by other organizations.
The gap conductance is based o calculated helius conductance until The contadt. conductance is based on data publichod contact occurs.
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by Ross and Stout.
The UO2 pcllcts arc dished about 1% and are ground to O'.0005" tolcrance on the dianctor.
The diametrical gap between clad and pelict is l$cid between 0.00C' and 0.003".
The Zircaloy-4 cladding is bought to a minimum tensile strength of 45,000 psi at 650 F rather than specifying the amount of cold work required.' The, purchase specification includes requirements on hydride orientation but the EM7 represcntatives wers unable to state specifically what these requirements /ere.
Clad resis-tance to cycling has been considered and although the margin was not stated BaW indicated.it was conservative..-
EM'I agreed to prov.ide the UO thermal conductivity curve used 2
(Figure 3-15) from the Duke pSAR) and the references used for this and for fission gas release rate and DO swelling (references 2
from appropriate chapters in the Duke PSAR).
Also, the clad resistance to cycling with :r.argins identified should be provided.
2.
FUEL ASSEMBLY MECHANICAL DESIC-N
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A canned fuel assembly is planned using a stainless steel can 031 inch thick with about 50% holes.
The design. includes
.l furnacc brazed stainless steel spaccrs.and Zircaloy rod cluster control quide. tubes.
BSW stated that the amount of' steel in core i
J is virtually the same as that with a canicss assembly and stain.
loss steel rod cluster controI guide tubes.
The stainless l
stecl cnns function as the a.ss.e=bly structural me:c.ber but are l.
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not required to withstand n:y sido loads.
Thus, caniccs asse: allies c'an be substituted.3t any time in the future.
3.
CORE THERMAL HYDRAULICS The core design is based on a calculated leahage flow of 5%.
This valuc seems low and difficult to realize without very close tolerances and special' attention to quality control.
This total by-pass flow includes the leakage flows in the 1
upper plenum and the flow up' the rod cluster control guide tubes.
Flow between assemblies is not considered leakage flow s'ince it is effective in hent transfer.
BSt! representatives stated that a 1/G scale model flow test is about to start to ver1fy the assuued flow maldistribution at the core inlet.
It was stated'that a 10% credit for mixing is used in the design.
The stated DMB ratio was 1.33 at 114% power using the BAW 160 correlation.
i 4.
CORE INTERNALS DESIGN
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The core internals are completely shop-assembled and fit up using a jig built from the as-built di,mensions of the pressure vessel'.
It is intended that there be no fita p of t'he internals ~ required u
in the field.
Bolted joints'aic used in the construction of the core internals to permit paral.kel construction of maaor portions of the internals.
To. prevent loosenir.g of bolted joints.the bolts are strength welded after ass nbly rather than tack wolded.
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et For examplo, hcx head bol:a and nuts normally have fillet wclds on three of the six facts dimension with dimensions and welding procedures sp2cified on the drawing.
These welds are inspected in the snac manner as strength' welds are inspected.
Thus, the final shop asseiably is connidered a permanent assembly; the bolted joints are not designed to permit dis' assembly.
The instrumentation guide tub.2s from the lower vessel head to the' lower grid plate are inse: ted af ter the internals are in place and.are held down against a apring loaded seal by the weight of the fuel assembly.
If pressure vessel inspection is required instrumentation guide tub,cs'will be removed prior to removal of-the core internals and will be reinstalled af ter the core interna.ls are reinstalled..
5.
PRESSURE VESSEL DESIGN The objective in the prosaure vessel is to obtain an NDT tc=pern-ture. of 10 F; however, it is expected that the' actual NDT' temperature of the materini will be in the iange of 10 to 40 F.
The shift in NDT with nyt is based on the data presented in
.ASuE. paper 63-?lA-100 D23 stated that the removal of the pressure vessel head.would take about' 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
It was further stated thattheuseofon'lytwostuhtensioncrswasbelievedtobe optinum since with.two stud ensioners crews could be working behind the stud tensionera 'to remove the studs and place spacers on them rather taan havin;. stud removal a scrics operation af ter loosening all s uds.
D.'d7 statnd thnt it is believed that O
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two cycles. will bc requires 1 for stud tensioning and that the amoug of time which c'd'ulk be savad by using three of four stud tensioner would be five or six hours at a ma::imum.
G.
STEAM GENERATOR BLU stated that the stean generator has slightly over 15,000*
tubes.
Thus, the 1% sparc ! tubes provided would permit plugging.
of 150 tubes before affecting' warranty performance.
- Further, BLU stated that it was )elieved that conservatism in the design heat transfer coefficients'should permit plugging of another*3 or 4% of the tubes and stil,1 permit operation at warranted conditions.
It was sta.ted that the average metal temperature difference between the tubos and the shell under normal operating i
conditions is about 15 F thus. minimizing stresses due t'o differen-
. tial thermal expansion.
i Theprimaryheadsofthesteamgeneratoreachhaveoneinspechion' (5 inches in diameter) and one manway.
port BLU stated that clips would be provided as necessns:y to facilitate installation of temporary shielding during tube plugging operations.
It was i
also stated th'at' tube plugging had been demonstrated in mockups of similar heads in a period of six hours.
However, the tube sheet. diameter in the proposed units is.approximately.10 feet, i
thus requiring entry' completely *into the head for access to tubes at the outer periphery.. The larger size v.111 thus result in somewhat higher dosos prcspcin; the same dose rates 5::ist l
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within the head.
The specific syntcm for temporary shiciding for the head has not yet boon designed nor have the special procedures for tube plugging f.n the large diameter tube sheet been fu1Ay developed.
Thus, it is difficult to say at this time how severe the problem of tube plugging might be.
However, it is clear that a great deal of ati:ention should be paid to this proble.m particularly.in the design of the bottom head area.
It may be desird.ble to consider...dditional manways or hand holes to provide improved access.?
I It was stated by BMI that the inflatable seals for the main coolant lines referred to in the proposal are commercially available nylon reinforced bladders.'
These seals are not required to withstand a~ primary coolant pressure head since the offset in the primary loop pip'ing is larger than the inside diameter of the piping thus permitting the nozzles to 'the pressure vessel to remain flocded while maintenance'is under way on the steam generator.
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a.e The in-cora instrumentation is to use self-powered detectors ani t.4crmocouples fabricate S fy ES'.f.
Ohe out-of2 core instru=cnta-05.on will use conventional loc chn=hers.
The arrcngement of'the
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in-core instrumentation is not as shown in the proposci and will i
be brought up to date.
The ot.ter tube or pressure boundary will l
he brought up to a level above thc tcp of the reactor vessel 4
to per=i: =anipulation of the ' instruments during r. efueling with-out the use of the seal.
EhW believes that the instruments strings can be inserted and withdraur. by han'd.
TestshavebeNn carried out which show that z' cas:icum force of about 50 pounds
, is required to insert the ins:runcats into the fuel asse=blies.
ESV now hcs an in-core instrument of the type proposed in' opera-tion at the Big Rock point plant.
Limited operation to date has been satisfactory.
ESU will supply calibration equipment for f
the in-core instruments but.does not offer a cask for replacing these in-core strings.
Sovcral important operating and main-tenance questions are invo:.fo ci n'nd special attention to this r
will be required.
S.
MISCELLANIOUS*
The coctainment design is based on the criteria. that access to all cuxiliary and safety syston ce.uipnent is poss:!.ble with a maxi =us dose rate of'25 cr/hr.
The missile shields shown in
.the plans are pre-cast concrctc bcams which are removed during refueling.
The core barrel and internals design is described on the revised plans provided!by BSW.from the Duke PSA2.
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plan shown in the proposal is act accurate in soveral respects anc. Shil will bring it up to date.
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No system is planned for continuous monitoring of containment penetration leak rates or for liner seams.
Such a system should be considered.
BMI is cons.idering use of sodium thiosulfate as a part of the spray system but the representatives present were not awarc of the status of this. investigation.
EMI recommends
.that all pools be stalnless steel lined.
In the refueling sequence planned by BMI an additional fuc1 transfer tube would not reduce the time required for the refueling operation, but would provide additional reliability.
The fuel transfer apparatus can be completely removed from the spent fuel pool outside'of containment for. maintenance.
Several systems questions were asked which the EMI representa-tives present were unable to answer.
It was agreed that answers.
to these questions would be provided by DMf at a'later date.
These included questions on the instrumentation provided by BMI for monitoring of primary coolant activity levels, and on safety i
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systems.
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'i D. L. Couchman i.
h J. K. Pickard 11/1/63 O
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