ML20054E802

Clarifies Basis for Proposing Addl Experiments to Confirm Structural Capability of Vessel Head to Accommodate Core Disruptive Accidents & to Benchmark Analytical Models Used to Analyze Vessel Head Response & Failure Modes

ML20054E802
Person / Time
Site:	Clinch River
Issue date:	06/09/1982
From:	Check P Office of Nuclear Reactor Regulation
To:	Longenecker J ENERGY, DEPT. OF, CLINCH RIVER BREEDER REACTOR PLANT
References
NUDOCS 8206140257
Download: ML20054E802 (4)

Text

.

W t

i Distribution .

June 9, 1982 / Docket File  !

NRC PDR l l Local PDR '

NSIC Docket ilo.: 50-537 CRBR Reading CRBR Staff Mr. John R. Longenecker Licensing and Environmental Coordination Clinch River Breeder Reactor Plant U. S. Department of Energy, NE-561 Washington D.C. 20545

SUBJECT:

CLItiCH RIVER BREEDER REACTOR PLANT, REQUEST FOR ADDITIONAL INFORMTI0fl Additional experiments similar to the Stanford Research Institute (SRI) l scale model tests could be useful in confinning the structural capability )

of the CRBR vessel head to accommodate core disruptive accidents and to bencisaark the analytical models used to analyze the vessel head response and failure nodes. -

Our initial request related to this subject was transmitted to you by letter dated May 14, 1932. This letter further clarifies the basis for our proposal for additional experiments (see enclosed).

The reporting and/or recordkeeping requirements contained in this letter

affect fewer than ten respondents; therefore, OMB clearance is not required under P.L 96-511.

If you require further clarification of our request please contact R. H, Stark, Project Manager (301) 492-9732. Otherwise, please provide your intentions regarding additional experiments to address the issues i discussed in the enclosure at the earliest possible date. l Sincerely.

/J/;S tY$;rz zu 4 v Paul S. Check, Director

/ CRBR Program Office Office of fluclear Reactor Regulation

Enclosure:

As stated cc. Service List e206140257 820609 PDR ADOCK 05000537 A PDR omer y ..C.@.BP.0 : NRR CRBRP0:NRR CRBRP0:NRR J.RBRp&:NRR " ' CR

' g .NRR CPBRP0:NRR ~ "

I HHolz/5 iSESrik BMorris WF6fteE sunm.ec k ~ kSd5Eck one> z. . . . . . . .. .!. .. .h.f.k.f.

de- ........

u%< J.

l unc ronu ais omeomacu om ' OFFICIAL RECORD COPY usceoa nem

l cc: Dr . Cadot H. Hand, Jr. , Director Barbara A. Finamore Codega Marine Lt.boratory S. Jacob Scherr University of California Ellyn R. Weiss P. O. Box 247 Dr. Thomas B. Cochran Bodega Bay, California 94923 Natural Resources Defense Council, Inc.

Daniel Swanson 1725 I Street, N.W.

Office of the Executive Suite 600 Legal Director Washington, D.C. 2J006 U. S. Nuclear Regulatory Commission Eldon V. C. Greenberg Washington, D.C. 20555 Tuttle & Taylor 1901 L Street, N.W.

William B. Hubbard, Esq. Suite 805 Assistant Attorney General Washington, D.C. 20036 State of Tennessee Office of the Attorney General L. Ribb 450 James Robertson Parkway LNR Associates Nashville, TN 37219 Nuclear Power Safety Consultants 8605 Grimsby Court William E. Lantrip, Esq. Potomac, MD 20854 City Attorney Municipal Building -

P. O. Box 1 Oak Ridge, TN 37830 _

George L. Edgar, Esq.

Morgan, Lewis & Bockius 1800 M Street, N.W.

Washington, D.C. 20036 Herbert S. Sanger, Jr., Esq.

General Counsel Tennessee Valley Authority Knoxville, TN 37902 Scott Stuckey, Chief Docketing and Service Section Office of the Secretary U. S. Nuclear Regulatory Comission Washington, D.C. 20555 Raymond L. Copeland Project Management Corp.

P. O. Box U Oak Ridge, Tennessee 37830

ENCLOSURE CS 760.174 Available test data from the SRI International Scale Model Tests seem to prove the capability of the CRBP, vessel as a whole to contain a 661 MJ CDA. However, we do not think the tests performed necessarily prove that the vessel head is capable of taking the simulated loads. From the hydrostatic test of the head, SM-1, it appears that the head failure mode would be disengagement of the Intermediate Rotating Plug (IRP) from the Large Rotating Plug (LRP) due to bending deformation of the LRP.

Because of the way the under-head shielding plates were attached to the head in the scale models, the bending defonnation of the LRP was over constrained. In fact, the bending sti'fness may have been at least an order of magnitude too high. Therefore, we believe that the tests performed to date cannot be directly used to confirm the head capability or to benchmark analytical methods.

The heads from the SM-4 and SM-5 test specimens experienced little, if any, plastic deformation during the previous test series. Therefore, they could be reused to perform additional hydrostatic tests, similar to test SM-1. The SM-4 head could be used as presently designad with the shielding plates in place. The SM-5 head and shielding plates could be modified to make it as prototypic as possible. Both these heads could then be hydrostatically tested giving a comparison between stiffnesses for the model head (SM-1), the model head with shielding plates attached as tested in SM-4 and SM-5, and the prototypic model head with shielding plates attached.

There tests could, conceivably, provide the data needed to successfully use the results of the overall SRI international test program in con-firming the vessel head design. However, at least one additional transient test may be required to prove the head capability for a 661 MJ CDA. The SM-6 specimen could be modified to make the head prototypic and then be used for this purpose. This test would be useful in meeting the second overall objective of benchmarking analytical models before they are used to predict response to higher energy CDAs.

The staff and its consultants have performed an in-depth review of the simplified analytical model presented in Appendix H of SRI International's Technical Report No. 4. To derive the simplified model, an equivalent uniform plate was substituted for a simplified, axisymmetric geometry of the three-plug vessel head. Dynamic response is calculated assuming the plate responds in the first vibrational mode. Therefore, the model applies only to response in the linear range. It predicts that the head would experience a peak displacement of 0.102 in. during a 661 MJ CDA.

No test data exists with which we can directly benchmark this model.

Analytically it can be modified by eliminating the effects of the shielding plates and then comparing its static response with the SM-1 test. This exercise shows that the model underpredicts peak displacement by factor of 2.4. Comparison of the volume-pressure relationship for the SM-1 test with a modification of the volume-pressure relationship (modified to eliminate shielding plate stiffness) used in developing

this'model provides additional evidence that the model is 2.2-3.2 times too stiff. If its predicted displacement is directly adjusted by a factor of 2.5, we predict a maximum displacement of 0.25 in. , which occurs at a static pressure of 1100 psi for SM-1. This is just under the failure pressure of 1160 psi. This assumes linear response. If the response goes into the nonlinear range, which it will for these high displacements, the response will be even larger.

One should be cautious not to draw too many conclusions from such a simplified model. However, the points made indicate the reasons for the difficulty in accepting either the experimental or analytical evidence now in hand as proof that the vessel head can withstand a 661 MJ CDA (112 i4J slug impact). Also, a suitable test program may provide enough information to meet NRC's objectives of estimating the ultimate capability of the head.

- --- - _ , - - - - - . _ - - - , .