ML19345G380
| ML19345G380 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 06/22/1973 |
| From: | Deyoung R US ATOMIC ENERGY COMMISSION (AEC) |
| To: | Maccary R, Stello V US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML19345G365 | List: |
| References | |
| ZECH, NUDOCS 8104070125 | |
| Download: ML19345G380 (3) | |
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JJi 2 21973 Docket 1:o0. 50-404 and 50-405 V. Stello, Accictsnt Director for Rcactor Safety', Directorate of Licensing R. R. Maccary, Acsistant Director for Engineering, Directorate of Licenciny, d NO2Til ANNA 3/4 - ROD EJECTION ACCIDENT Encloacd is a copy of a rco.ucst from the ASLEP for suppleucatal teaticony indicating the extent of the occff's consideration of the rod ejcetion I
cccident and its revicu of the cpplicant'c analycia. Plecsa nota that this requcct ic cccociated with the supplenent:1 tectinony of Joacc 7. Scott that uns for'tarded with cy acno to you dated June 4, 1973.
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that both rec.ucats be anc cred in one responce in the fora of cupplcantal tccticony suitabic for subciscion directly to the ASL2?. Picacc cead copics to D. Kartalia and S. Lewis. If you cannot provide tha tcotir.ony.
by June 22, 1973, please lot ma kncv your schedule for your recponse.
4 Original.e!J'd D R.. C. D.qung R. C. DcYoung, Ascistent Director for Precsurized t! ster Rcactor:
Directorate of Licensf.n:;
Enclosure:
ASLLP ltr dtd 6/13/73 cc:
J. Ucudric D. 1:artalia S. Louis DISTRIBUTION Docket (2)
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2 Based on the above summary, the Staff believes that the B&W calculations of an assumed rod ejection accident contain sufficient conservatisms, both in the initial assumptions and and in the analytical models, to insure that pressure vessel damage would not occur and that any resulting radiation doses to the public would be well within the 10 CFR 100 guidelines.
B&W also performs an analysis to estimate the control rod reactivity worth required in the event of a rod ejection accident,to damage the y
reactor pressure vessel. A calculation is done to esti= ate the energy equivalent of TNT that would be required to strain the vessel up to 50%
ultimate strain. This appears to be a highly conservative calculation 3
since the assumption is made that the integrated energy content of all the
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fuel in the core due to a. rod tjection accident is available for release to the vessel wall even though the 280 cal /gm fuel failure threshold is not reached. However, we have not reviewed the specific details of their procedure for. analyzing the response of the vessel to the hypothesized energy release, as we do not believe such energy release can be realized in that short time span.
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a NORTH ANNA UNITS 3 & 4 ROD EJECTION ACCIDENT The Staff believes that because uncertainties exist concerning the adequacy of models to calculate control rod ejection accident consequences, a conservative approach is necessary.
Our current position is to limit the calculated maximum credible control rod ejection accident consequences such that the maximum energy density (enthalpy) in the fuel at any time during the accident is sufficiently low to preclude dispersal of fuel to the primary system.
Based on experimental evidence from the TREAT and SpERT CDC (Capsule Driver Core) tests, this prompt fuel failure criterion has been taken as 280 cal /gm, averaged radially across the hottest fuel tellet.
Independent calculations were performed in June 1971 by our consultants at Brookhaven Eational Laboratory in order to verify the calculational techniques used by B&W in analyzing the consequences of a rod ejection accident at full power. The BNL results agreed quite well with the B&W results, the BNL calculations yielding a slightly lower value of peak fuel enthalpy.
Based on these calculations, the Staff felt reasonably satisfied with the analytical methods used by B5W.
B&W has verified their procedure for the analysis of the reactivity worth of control rods by comparison with critical experiments performed at the B&W Critical Experimental Laboratory. The Staff, therefore, has reasonable confidence in the B&W prediction of maximum control rod worths for various operating core conditions. Although B&W specifies a maximum control rod reactivity worth of 0.65% Ak/k as a Tech Spec limit, calculations show that rods of this much worth would only occur during startup when the core was i
still in a suberitical condition.
In fact, the maximum worth of a control rod during full power operation (where the results of a rod ejection accident are the worst in terms of peak enthalpy and rods in DNB) is shown to be only 0.32% Ak/k. B&W has, nevertheless, performed parametric studies involving ejected rod worths as high as 0.8% Ak/k for both full-power and 10 3 of full-power and has found that even for these high assumed rod worths, peak fuel enthalpies approached only 220 cal /gm, well below our fuel failure criterion of 280 cal /gm.
Since these rod ejection accident calculations resulted in peak fuel enthalpies less than 280 cal /gm, prompt fuel rupture with consequent rapid heat transfer to the coolant from finely dispersed molten UO2 was assumed not to occur.
The pressure surge was, therefore, calculated on the basis of conventional
, heat transfer from the fuel and resulted in a pressure increase below the vessel design limit.
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Udtgg M Docket Nos 50-338 JUN 21673
^0-3_39 50-404]
50-405 and APPLICANT:
VIRGINIA ELECTRIC AND POWER CO:!PANY (VEPCO)
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FACILITY:
NORTH ANNA PO*JER STATION (NA), UNITS 1, 2, 3, AND 4 s
SUMMARY
6F MEETING HELD ON JUNE 18, 1973 TO DISCUSS CHLORITE SEN!
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On June 18, 1973, representatives of VEPCO met with the Regulatory staff to discuss a " chlorite scam" in the excavations for Units 1, 2, 3, and 4.
i The discussion included areas of interest to the Site Analysis Branch.
f A list of attendees is enclosed.
1 The significant points discussed are summarized below.
I 1.
Feature Description The seam is associated with a fault which has been traced from the
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excavation for Unit 1 through the excavations for the other units.
i The fault varies in width from a few inches at Unit 1 to about 6 feet j
at Unit 3; its width reduces to a few inches as it leaves the Unit 4 excavation. No indications of movement were observed, by VEPCO, in the i
excavations for Units 1 and 2.
However, some indications of movement in the order of inches to several feet, possibly as much as 20 feet, were observed in the excavation for Unit 3.
The fault has also been traced by surface trenches (10 feet deep) to a point about 2000 feet west of Unit 4.
The description of the fault has been recorded in all t
excavations via color photographs and detailed maps. The Regulatory staff observed the exposed fault at the excavations for Uni *.s 3 and 4 l
and at trenches 1, 2, and 3.
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Investigative Program j
The applicant has established a comprehensive program to investigate the fault. The programs includes detailed geologic mapping along the i
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fault, soil gradation analyses, mineralogy studies and age dating techniques, and petrofabric studies.
At the time the program is about 80% complete. The mapping of the fault out to 3-5 miles from the excavations and the dating of the soils capping the fault are still in progress. A final report is expected in about 10-12 weeks.
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Preliminary conclusions VEPCO's tentative conclusion is that no movement has taken place along the fault for more than one million years. The Regulatory staff and 2
their consultant did not observe any evidence that would contradict that conclusion. The staff and their consultant stated their opinion that there is reasonable assurance that the final report will confirm the preliminary conclusions and that there is no reason, at this ti=e, to alter the
' staff's previous conclusion regarding the issuance of a construction permit for Units 3 and 4.
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Future work
'l VEPCO intends to complete the investigative program and file a final
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report in 10-12 weeks. VEPCO will backfill the trenches and mark the location of the sean at the surface in case other investigations may be necessary in the future. VEPCO will continue with the excavation for Units 3 and 4 as permitted prior to decision to issue the construction permits.
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Robert L. Tepgus n, Project Manager Pressurized Racer Reactors Branch No.4 Directorate of Licensing
Enclosure:
j Attendees
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x; North Anna Site Meeting 6-18-73
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J. McWhorter, Dames & Moore R. McEldowney, Dames & Moore f
Dr. A. J. Hendron, Jr., Consultant, Stone & Webster I
N. Lee Worth, Stone & Webst'er*
J. Briedis, Stone & Webster P. R. Beament, Vcpco E. A. Baum, Vepco C. M. Robinson, Jr., Vepco Fred M. Alligood, Jr., Vepco R. A. Miller, Vepco Iowell A. Douglas, Dames & Moore, and Rufgers U.
Dr. Brian Ellwood, Dames & Moore Dr. John Gibbons, Dames & Moore Fred N. Houser, USGS A. T. Cardone, AEC-L R. L..Ferguson, AEC-L N
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Michael W. Maupin, Esci.'
David E. Kartalia, Esc.
Hunton, Hilliams, Gay & Gibson Regulstory Staff Counsel 700 Enst Main Street U.S. AtonU c Eucrc.y Cc,.nission Richmond, Virginia 23212 Washingcon, D.C.
20545 Re:
Virginia Electrie & Power Comprny (North Anna Power Station, Units 3 and 4)
Dochet Nos. 50-40's anel 50-405 Gentlemen:
.The board has roccived the opplicant's motion for.the admission of certain documents in evidence, these documents including those attached to the motions.
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In connection with the supplemental testiuony of James Scott' ubich in of fered in evidence as the applicant's oronosed Exhibit 20, and ubich supnlics further analysis.of ihe rod ejection accident in response to the board's requast (TR 720),
the board would like to have additional informacion on two
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pointst A.
It appears the report NOLTR 63-140 stresses that
. the propertien of the vessel material, as they relate to containment, "must not be negated in tima by ' flaws, MDT (nil ductility te!.,perature) considerations, radiation effectc, stress concentrations, hir'h temix.rn eurcs, cycling' etc." (p. 33). _ Poes the applicant's ana' lysis take into account the af.Cects of radiation, flaus, and metal thickness
.on the properties of the material?
If so, to what extent and hou han thi:: been done?'
If not, what data and/or enalysis show that such cffects would be negligible?-
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The Applicant's analysis in bas.ed on the assumotion that the energy relenne in the rqaccor would occur over' a time men::ured in milliseconds to seconds, and that the effcces v ould be e.,re like those.produc-d b; a nropcliant h
loadin. ti.an by a TEf c::plesion.
HOiJR A3-lA0. inunrs to loadinr. prod. ices dahhr.c bv indicate that the propellent f
huild un of internal pressure rather than by chock lo:' ding (p. 17 ).
In addition, "Although the propcOnnt experimon'es 8/090}O!kf
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e were conducted in vencels with rir;id chd closurcs, the uniforuity of loadinr: over the fall vesnel lentth renulted in defor:.:'tions similar to those of the'open end explonions experiments."
(p. 90).
In li;;ht of chese considerations, what experimental data and/or analyses ' provide the basis for applicant's use of an equivalent prescure ves.sel wall thickness of 11.51 inches to account for.the effect of the thermal shield and core barrel in its calculacions (PSAn
- p. 14 - 53 ) ?
To 16.at e:ctent would the proposed use of the vont valves in the cc,re support asteably affect the value assi ned to the equivalent pressure vessel vall thichnecs?
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What " rod worth marp,in" would the annlysin yield. if the pressure vensel wall alone were required to with' stand the pressure rise?
The hcard uould like to hnve thin additional informatien supplied in the form c supplemental testimony, and would also like to have supplemental testimeny of the staff indicatint; the c:< tent of its copsideration of the centrol
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rod ejection accident and its review of the applicant's analysis.
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In view of the applicant's reliance on the report NOLTR 63-140, the board would also like to have the record i
. supple:aonted by a copy of this report to be offered in evidence by the applicant or by the staff.
In the mean time, the determination of the applicant's motions of May 24, 1973 uill be held in abeyance.
Sincerely, pl 7. fl0[-< 0 l
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Sidney C. Kingsley i
cc:-
C. T. Kipps, Jr., Esq.
C. J. Savage, Eng.
R. 1;riggs E. Chanlett c
D. lic ad K. McCollom F. Karas D
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I MAY 171973 NOTE TO FILES NOTE OF TELECON - NORTH ANNA 3/4 GEOLOGY CONCERN Ashley Baum from VEPCO called to report that they have discovered a chorite seam in the excavation for North Anna Units 3 and 4.
It came to VEPCO's attention May 11, 1973. Dames and Moore has been called in to evaluate this finding. VEPCO expects to be prepared to meet with the Regulatory staff in about two weeks to discuss this Mr. Baum said that from a photograph he had seen the seam matter.
cppears to be rock folding.
It is located in the contain=ent area cnd is visible on both walls of excavation starting at a level about ten feet below surface and extending to the bottom. Mr. Baum cnticipates that the Regulatory staff and its consultants may wish to visit the site prior to the projected meeting in Bethesda.
By copies of this note, H. Denton and W. Gammill are being alerted to this concern.
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. pchwencer, Chief
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Pressurized Water Reactors aranch No. 4 Directorate of Licensing cc:
A. Giambusso R. C. DeYoung H. Denton S. Lewis, OGC i
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