ML19212A524
| ML19212A524 | |
| Person / Time | |
|---|---|
| Issue date: | 06/28/1976 |
| From: | Knuth D NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | Moeller D Advisory Committee on Reactor Safeguards |
| References | |
| RIL-005, RIL-5, NUDOCS 7912140440 | |
| Download: ML19212A524 (2) | |
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3 Dr. Dade W.11oeller, Chairman Advisory Co mittcc on Reector Safeminrds T.reste Center for Environ. ental llealth f0 School of Public Health 0
1 Harvard Universit'-
1.1 1.b J U U J WNA Boston, Massachusetts qD lil I
Dear Dr. Koe.ller:
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a SRI C0FTIKr4 TOP.Y PPISSLT1. VTSSEL TEST tr.iT>ER Tr7V.U. TIC LOADIt:C This letter is one of a series to transmit safety research infor-mation to you for any assistance it may provide the ACRS.
The RSSI progran str.ff at OTGL has successfully tested a flawed, 6-inch thick intermediate test vasoci under a sustained pneunatic load. The test, designated as I,'C;-7A, was completed on June 13 at the Navy Surface 'icapons Center, Dahlp.ren, Virginia. The primary objective of the test was to verify the analytical prediction of non-catastrophic vessel failure under a sustained pneunatic load. This test was conducted in answer to a request by the AU!S on 11 arch 8, 1971, to deternine the mode and consequences of-vessel failure under 7
pneu::.atic loadinF. conditions. A secondary objective was to evaluate residual stresses in the repair veld in the test vessel. The result of the e.xperitent confirmed the pretest prediction that the sustained pucucatic pressure in the vessel behind the crack did r.ot cause con-tinutas extension of the crack; the test also revealed little if any deviation in strain measurenants in the vessel repair weld during test.
For the ITV-7A tect, the vessel was first pressurized to 1.1 r operat-int prosaurc and then depressurized to evaluate any effect of the si:-
ulated proof test pressure on the residu.11 stresses in the repair veld..
Ao noted above, ti.c initial data sher very little if any deviation in strain measurenents in the repair veld becueen loadict and unloading the vessel. Tne vescal was then pressurized to about 18,000 psi and depressurized to below 10,000 psi to hcip extend the flav by fatigue.
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Repressurizction was then undertaken and at 20,900 psi crack growth vcs sufficient to cause rapid separation of the final renaining liga-twen t. A thin stainless steel boot velded under the flav region in 1568 081 7912240 e q y ()
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Pr. 1W e ". % 11c-JUN 2 8 N/6 ITV-7t. prevented loss of pneu:natic pressure at failure and obviated the necessity to natch the flow rate and voluzae of discharge that could be calcalated for a through-wall breach in a FWR vessel. Even though the flatr extended dynattically and there was a sustained load to drive it, crach e~. tension essentially stopped once the through-vall condition tras reached. Only increasing pressure would have caused ad/.itionni slou crach growth until critical fine size were reaci. cit and unstable ra;'id fracture could be predicted.
This test shows that the analytical predictive capability for vessel failure under pneunatic load is well founded, so that we can accurately predict vessel behavior under such conditionc. Moro it::portantly, the test shows that at upper shelf level toughness under the very hishast r
pressure that coult'. be predicted for a PWR under accident conditions (about 3,750 psi for a PW't, scaled to about 18,000 psi for ITV-7A) a throu!;5-wall flaw will not result in a catastrophic failure so that ECf: water car. be retained in the vosoel.
Sincerely, c..t W.
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Donald F. Knuth, Director Division of Reactor Safety Research Office of Nuclear Regulatory Reser.rch cc:
R. F. Fraley, ACRS T. S. !kCroless, t.CRS 4
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