ML20024B277
| ML20024B277 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse, Crane  |
| Issue date: | 10/07/1977 |
| From: | Lauer J, Lazar A BABCOCK & WILCOX CO. |
| To: | Domeck C TOLEDO EDISON CO. |
| References | |
| TASK-*, TASK-03, TASK-06, TASK-07, TASK-3, TASK-6, TASK-7, TASK-GB BWT-1579, GPU-2412, NUDOCS 8307080200 | |
| Download: ML20024B277 (2) | |
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- 333 A. II. Lazar actober 7,1977 D. B. Tulodieski P
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J. D. Lenardson 303 Itadisen Avenue J. C. Lewis 6
- Toledo, Ohio 43552 D. J. Delacroix r
E. C. riovak/2c
Subject:
Toledo Edison Cc: pany E
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DEPRESSURIZAT:C:: EVENT OF SEPTC;EER 24, 1977 E
Davis-Besse Unit 1 t
1155-14 c.
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Dear fir. Domeck:
Our letter E!.T-1578 dated Octcher 5,1977 advised that Edf is revieaing the available data regarding the de:ressurization event of Septe.-ber 24 and we consider that there has been no degradatica of safety in the plant. By telecon of October 6, you have E,
s advised that I;RC.would like c=re informatica regarding the basis for our conclusions.
F-The ce=;:enedts.are desig.ed for ferty cycles of a d:presguri:stien transie't in which n
the pressure drops 1/03 pst and the te :erature drops 62 F in fifteen minutes. In
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this actual transient the pressure dro;;cd 1250 psi and the tc perature dropped 45'F
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in 7.5 cinutes. The stresses due to pressure are net sensithe to tice in these load-ing ranges. Since the pressure change of the actual transient is less than the g
pressure change of the generali:ed transient, the stress effect cue to pressure would be less than calculated for tk.e generali:ed tra.sient. Although the rate of tgeperature change is higher in the actual transient', the overall te ;erature change is 17 less.
t These two differences tend to offset each cther such that the resulting stresses for the actual transient were no worse than tne calculated stresses for the design transient.
i-One steam generator a;sparently boiled dry during the depressurization event because the auxiliary feed,ater turbine failed to cern up to speed. The design transients L
include twenty cycles in which feed.<ater fice is icst to one generator and the generator is evaporated to a dry pressuri:ed c=ndition. The introduction of fee &ater G
into a dry stea= generator is a design c:nditica and will have no harmful effects.
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The major concern while the steam generator is dr/ is variatien in the tube-to-shell temperature differences. In the actual transient the steam generator was dry for a short period of time and the generator re sined pressuri cd. During this timg of ap-proxicately 13 minutes, the reactor coolant tee;:erature drep;cd a total of 50. This tamperature dn:p was not sufficient to cause excessive stress or permit defonnation E
of the tubes, and is within the established design lic:its.
F The actual stresses were no wc se than the calculated stresses frem the ' design transients f
and consequently the fatigue usage resulting frem the actusi transient is no worse than that for the design transients. The predicted fatigue usage for this transient is the F.
I sane as that of one design cycle of rapid d:pressuri:ation and one design cycle of L
startup of a dry steam generator. There is no change in the csiculated.fstigue life of the cor.ponents. Since the stresses and defor:.:tions resulting from design transient analysis are acceptable, there is no reason to cxpect oventressing or material defonnatic in the RC system due to the actual transient. He do not consider it necessary to e
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conduct a detailed inspection of hangers and restraints for evidence of damage or deformation.
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The reactor coolant pu os were all operated at er near saturation pressure (A2 and B1 for about one cinute and Al and 82 for about 45 minutes). There is so=e risk o cavitaticn damage to the impe11crs and also a risk ths.t saturated steam would cause dry bearir.gs and resulting da age.
L In addition, radici offsets due to cavitation may dacage the seals.
flow for about 1-3/4 minutes after containr.ent isolation valves were clo 9
reviewed these conditicas with the pu: p canufacturer and concluded that the risk of
!!e have dacage is stall.
Disassedly and inspectica of the seals, bearings, and ir:sollers
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would not provide 1 ggt assurance that thay will o;erate pre;erly.
have recc::nended that the cu ;s be instru ented to censure shaft vibration, s,eal p
Therefore we cavity pressures, RC pressure, standpi;e leakage, and seal injection flea and targerature.
Mode 5 and the cbserved ; ara sters shcu no irif caticn.of damage.Each b
have st=fler test ru s in :*cte 3 v. hen che PJ orassure is above 1300 psi.
!?e expect to L
be safely operated as designed. runs also sh:w no indication of da: age, B&'.1 wo If these I
l, B&!! has evaluated the 9/24 fr.cident with regard to its effects upo'n fuel perforcance
.This conclusten is based upon the following consideraticas:and has co D:
h.
Prior to the subject transient the react'or had been operating for ap-I prwxicately cne week at a caxie.:n of 151 of ratad pcuer; fr-ediatel prior to trip the pcuer level was n.prc.s!:.stely 10t of rated pouer,y therefore, the heat gaseraticn in-the core (decay heat) during the F
depressurizatien transient was extre..ely 1ca and significantly less than that produced by the reactor coolant pu ps.
The core burnup'on 9/24 was approximately.1 EFPD.
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During the transient the caxicus fuel red in' tert:a1 pressureits bee n conservatively esticated to have been no : ore than 300 pst greater than L
the minicu= RC systen oressure; the raxt:,;:: fuel red cladding tec erature was 550F.
The tensile stresses icrosed on th: cladding as a resu;lt of
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the 300 psi pressure differential existed for less than ene hour.
g cladding with low irractation exacsure ene.c4 to this temperature / pressure For codination no defor:.ation or failure v.uld he predicted.
- J Reactor coolant teccarature, pressure, and (1cu rate data obtained during G
the course of this transient indicated that th3re was no significant heat I
generaticn in the reactor core; this data further indicates that no i-significant boiling occurred in the core.
Yery truly yours, r
A.
azar nior Project Manager
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.1.auer, Project Manager
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