A06028, Forwards Addl Info Re Application to Amend License DPR-65 to Allow Storage of Consolidated Spent Fuel in Spent Fuel Storage Pool,Per NRC Request

Forwards Addl Info Re Application to Amend License DPR-65 to Allow Storage of Consolidated Spent Fuel in Spent Fuel Storage Pool,Per NRC Request

ML20213D393
Person / Time
Site:	Millstone
Issue date:	10/30/1986
From:	Opeka J, Sears C NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:	Thadani A Office of Nuclear Reactor Regulation
References
A06028, A6028, B12314, TAC-61658, NUDOCS 8611120058
Download: ML20213D393 (13)

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October 30,1986 Docket No. 50-336 B12314 A06028 Office of Nuclear Reactor Regulation Attn: Mr. Ashok C. Thadani, Director PWR Project Directorate #8 Division of PWR Licensing - B U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Gentlemen:

Millstone Nuclear Power Station, Unit No. 2 Storage of Consolidated Spent Fuel in May,1986,(I) Northeast Nuclear Energy Company (NNECO) submitted to the NRC Staff a request to amend its operating license, No. DPR-65, for Millstone Nuclear Power Station, Unit No. 2, to allow storage of consolidated spent fuel in the Unit No. 2 spent fuel storage pool. As a result of the NRC Staff review of this proposal Information.h)theThe NRC purpose Staff forwarded of this letter to NNECO is to provide a Request the NRCfor Additional Staff the requested information.

Question #3.1.1:

Reference 2, page 19, lists ASTM-A240 and ASTM-A479 as materials for the new spent fuel racks while Reference 1, page 4-6, lists ASTM-A240 and ASTM-A276.

Please explain the difference. ASTM-A276 is not listed in the reviewer's ASTM specifications nor is it an ASME code material under the normal corresponding SA-276 designation.

Response

The material listing of Section 4.b on page 4-6 of the license amendment request is not complete. Section 4.b should have read, " ASTM-A276 or ASTM-A479," to (1) 3.F. Opeka letter to A.C. Thadani, dated May 21,1986, " Millstone Nuclear Power Station, Unit No. 2 Proposed Change to Technical Specifications Storage of Consolidated Fuel."

(2) D.H. Jaffe letter to 3.F. Opeka, dated August 27,1986, " Technical Evaluation Report Millstone 2 - Storage of Consolidated Spent Fuel Technical Specification Change Docket No. 50-336.

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n he consistent with the material shown on page 4-42 of the license amendment request. ASTM-A276 was an option that was considered for use in fabrication of

the spent _ fuel racks, however, ASTM-A276 was not used. The documentation packages and material certifications provided with the spent fuel racks show  ;

that ASTM-A240 plate and strip and ASTM-A479 shapes and bar were used in 1 fabrication. Both ASTM-A240 and ASTM-A479 are ASME code materials. - '

l Question #3.I'.2:

Reference 1, page 4-11 calls out 3000 psi concrete for construction material for the spent fuel pool / auxiliary building. Three pages later, 4800 psi concrete is listed as a concrete material property for the mathematical model. Reference 3, page 26, calls out 3000 psi concrete for pool material. Please explain the apparent conflict.

Response

The construction material used for the Millstone Unit No. 2 spent fuel pool is called out as 3,000 psi, 28-day strength concrete. The actual test cylinder concrete compressive strengths were obtained for the spent fuel pool structure.

The test reports showed that the concrete had an actual minimum 90-day compressive strength of 4,800 psi. The value of 4,800 psi was therefore used in concrete strength calculations. Per ACI 349, the appropriate strength reduction

factors'were also used in the calculations to account for, among other things, variations in material strengths of the construction material.

Question #3.1.3:

Reference 2, Section 4.2, starting on page 20, discusses a rather extensive test program to be used in conjunction with the analysis of the Spent Fuel Rack System but the testing program and the use of resulting data is not addressed in the SAR (Reference 1). Please discuss as the testing portion seemed to be an important step in doing a reliable analysis of the Spent Fuel Rack System.

Response

Three different series of structural tests were conducted on a prototype consolidated fuel storage box (CFSB) to obtain static and dynamic properties of the box and fuel rods for incorporation in the computer models. As the name implies, CFSBs are the boxes in which fuel rods are stored in the spent fuel racks after consolidation. The test series were:

1. Static load-deflection tests to measure the lateral stiffness of the box with fuel rods.

2. Static compressive tests on a short box section to measure the local wall stiffness of the box.

3. Forced vibration tests on a loaded box in air and in water to measure natural frequencies, mode shapes, critical damping ratios, excitation forces, and magnification ratios.

Results of the tests were evaluated and correlated with the analytical models to obtain a computer model of the CFSB loaded with fuel rods.

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LATERAL LOAD DEFLECTION TEST 5 The objective of this series was to obtain the static deflection characteristics of

• the CFSB when subjected to push-pull lateralload cycles applied at the center of the span. A full length prototype was specifically' fabricated for the test'and was pin-supported at each end. It stood vertically on the test stand and was filled with depleted fuel rods on a triangular pitch. Two fuel rod compaction ratios were tested,378 rods loaded in rows of 18 (tight compaction) and 352 rods in the.

same configuration (intermediate compaction, i.e., 2:1 consolidation). .

FORCED VIBRATION TEST The objective of this series was to identify the vibrational characteristics of the consolidated fuel storage box in air and in water when loaded with fuel rods at Lthree different compaction ratios, and also when empty. The test CFSB and the

. fuel rod configurations were the same as in the lateral load deflection test, and the compaction ratios were: tight (378 rods),-intermediate (352 rods) and loose.

.(306 rods). The third compaction ratio was included because the fuel rods were expected to affect vibration damping, whereas they had practically no effect on static deflections of the CFSB.

Parameters of interest were the CFSB's natural frequencies, associated mode shapes and modal critical damping ratios. These parameters were determined over a wide range of sinusoidal and constant displacement excitations induced through the lower support pin.- Furthermore, the required forces and the strain distributions along the CFSB were measured for each response.

LOCAL STIFFNESS TEST The . objective of this series was to obtain the local stiffness property characteristics of the consolidated fuel storage box when loaded with fuel rods.

Two compaction ratios were tested, namely tight (378 rods) and intermediate (352 rods). For this purpose, short sections of the CFSB, filled with depleted fuel rodlets, were compression-tested in a horizontal position at several load increments in a tensile test machine. Load versus deflection characteristics were obtained for the upper end, mid-section and lower end of the CFSB. The >

upper and lower ends included the locking cover and the box floor, respectively.

Loading was applied to the upper surface of the box as a transverse line load in the center of the length for the mid-section, and at the upper and lower ends.

-The box section deformations were measured by the tensile machine extersiometer and by dial indicators. CFSBs in the spent fuel racks are not supported at their upper ends. The upper end test section was therefore cantilevered from the tensile machine support plate in order to include a beam mode effect-In the measured deformation and stiffness characteristics of the upper end. After completion of all three types of local stiffness tests in the elastic region, the. three types were repeated, extending loads beyond the linear range. The plastic range was characterized either by a plateau on the load versus deflection curve or by large deformations of the box walls.

CONSOLIDATED FUEL STORAGE BOX MODEL A CESHOCK model was developed to simulate the structural characteristics of the consolidated fuel storage box (CFSB) loaded with fuel rods in water. The p._,weo =

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CFSB model properties.were developed in steps. First, the static lateral load

. deflection test data were evaluated and analyzed to identify the static stiffness,

- shape and boundary conditions of the CFSB as ~ tested. A' static model was

' derived with stiffness obtained directly from the CFSB structural dimensions, and the calculated results were compared with the test results. -In _the next step, the structural weight and hydrodynamic effects were added to obtain a lumped-mass dynamic model of the CFSB and fuel rods. .Results calculated with this model were then compared with data from the forced vibration test.

. MODEL-TEST CORRELATION RESULTS- '

The results of the lateral load deflection and forced vibration tests were compared as described in the following paragraphs with calculations using the CFSB model. : Data from the CFSB local stiffness test were used to derive ,

elements in the combined storage rack and CFSB model to simulate impacting  ;

between the CFSB and the spent fuel storage rack.

' Lateral Load Deflection Test Statistical analyses of the test data were performed and average deflection shapes of the deformed consolidated fuel storage box obtained. The data.were analyzed in categories related to the compaction ratio and the maximum displacement value (i.e., small or large deformation ranges). It was found that

.the number of fuel rods and the magnitude of the displacement did not significantly affect the box stiffness. .The stiffness of the CFSB and fuel rods appears to be primarily a function of the structural dimensions and material of the box -alone.- Figure I compares static displacements calculated with the computer model and the test data. Two calculated displacement curves are shown, one for a CFSB simply supported at both ends and one for fixed support at both ends. Agreement between the simply supported curve and the data from the test,~ in which the CFSB was simply supported,is good.. -

Forced Vibration Test The consolidated fuel storage box was excited at the bottom with a sine-sweep for various levels of input displacements. The double-amplitude displacements  ;

ranged from 0.005 to 0.060 inches. The sine-sweep tests yielded the natural frequency of the CFSB and a measure of damping. In addition, the maximum displacements at various elevations, strains and the base reaction force were measured. Selected data are plotted in Figures 2 through 5 inclusive.

!' As previously noted, the static lumped-mass model of the CFSB was modified to l

include the weight of the fuel rods and hydrodynamic effects for tests conducted

in water. Each modification was unique for the particular test condition being

simulated. Selected test measurements were compared with model properties and simulated dynamic responses.

It was found that the frequency of the empty CFSB in air is predicted well by

' . hand calculations based on the structural dimensions of the box. For the empty

• CFSB in' water, the effects of water on frequency can be predicted well through standard theoretical calculation techniques. The water can be represented as

additional . lumped-weight consisting of terms for the contained and displaced i -water. When fuel rods are placed in the CFSB, the frequency changes due to the additional weight of the rods. The rods do not provide any significant stiffness contribution.

4

- Table I compares first mode test and model frequencies. The agreement is good.

The size of the test tank'did not have a large effect on the first mode frequency of the CFSB. During the testing, it was noticed that tank vibrations occurred at

. the second resonance near 30 Hz. Similarly, it was observed that the I-beam strong-back vibrated near the third resonance of about 40 Hz. Since typically

seismic motions-do not exhibit amplified response greater than 25 Hz, in this' stuoy the emphasis was placed on the first mode of vibration.

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Time; history model simulations of some test sequences were also conducted to:

i compare responses of other quantities, such as damping, base reaction force and displacement. ' -A comparison of test- and model parameters for ' one such simulation is included in Table 2. It' can be seen from Figures 2 and 3 that damping varies more than frequency with the input amplitude. Therefore,in the model simulation of a particular test, the damping value from the individual test should be applied in t_he. model. When this was done as shown in Table 2, the agreement of the model and test data was excellent.

Consolidated Fuel Storage Box Local Stiffness Test Short sections of .the consolidated fuel storage box containing fuel rods were each ' subjected to a transverse line load on the uppermost wall while resting horizontally on a flat surface. Deflections at various locations on the CFSB.

walls were measured as a function of load. In one test, the load was applied at the end of the section. In the first of these two' tests, the box section under the load line included the CFSB floor, and the test measured the local stiffness of the lower end of the CFSB. 'In the second of the two tests, the box section under the load line included the CFSB cover, and the test measured the local stiffness of the upper end of the CFSB.

The test results showed that the behavior of the CFSB is complicated under this type of load and that it exhibits a great variation in stiffness values. At high loads local yielding or buckling of the box walls occurs. This is depicted by the drastic changes in the stiffness values. At the bottom and upper sections, an increased load can-~ be attained because of the support provided by the end fixtures. In general, the overall stiffness values are significantly higher than the CFSB stiffness in the beam mode exhibited in the lateralload deflection test. In the beam mode, the CFSB supported'its ends and loaded at the center exhibits a stiffness of about 16,600 lbs/in. The local CFSB stiffness testing shows values from 100,000 to 300,000 lbs/in.' CFSB impact stiffnesses for the consolidated fuel storage box were derived from these values. Because the measured stiffness varied with the applied load level, the actual stiffness values to be used in fuel j rack seismic analysis for CFSB impacting were based upon the site specific i seismic excitation.

i Question #3.2.1:

' The Basis for Limiting Condition for Operation 3.9.6,3/4.9.7, Crane Travel -

Spent Fuel Storage Building, states that, " specific analysis has been performed for the drop of. a consolidated fuel storage box on an intact fuel assembly."

i Where is the analysis?

Response

An analysis was performed by C-E which considered the drop of a fully loaded i consolidated fuel storage box onto a stored intact fuel assembly. The total droo L

height for such an accident is twenty-eight (28) inches to the top of the fudl L

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' assembly). A nonlinear multi-spring / mass model (Figure 6) of a fully loaded -

I consolidated fuel storage box dropping twenty-eight (28) inches onto the top of a stored fuel assembly was developed.

The CESHOCK computer code was used to perform a dynamic nonlinear analysis to determine the maximum impact load in the stored fuel assembly due to the

-drop. The result of that analysis was a maximum impact force in the stored fuel assembly of 100,000 lbs.

The calculated peak impact load was then statically applied to the fuel assembly -

to assess its structural Integrity. Assuming no lateral deformation results in the entire impact load axially compressing the fuel assembly with the guide tubes ,

compressing first until the ultimate stress of 80,000 psi is reached. This ultimate guide tube stress is reached at a load -of 37,840 lbs. The remainder of the 100,000 lb. load is carried by the fuel rods as the grid cage crushes and the load is applied directly to the top of the fuel rods. A load of '148,750 lbs. was calculated to be required to produce the yield stress of 25,000 psi in the fuel rods. : Since this load is greater than 100,000 lbs.,' the fuel rods will not yield, and the analysis demonstrated that the stored fuel assembly is capable of absorbing the kinetic energy of the drop with no fuel rod failures.

Question #3.3.1:

Reference -2, Section 1.4, page 7, discusses a reactivity meter to be used for dete mination and verification of burnup. This is not mer,tioned in the SARs

- discussion of reactivity determination for storage of spent fuel. Please explain.

~ Response:

The reactivity meter discussed in Section 1.4, page 7, of the March 30, 1984(3) letter, as stated in the letter, is a state-of-the-art device which is _ still' under development. The engineering design reviews are still ongoing. The determination and verification of burnup is currently controlled administratively and - the described reactivity meter is not required for determination of reactivity for the storage of spent fuel.

We trust you find the above information responsive to your request.

Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY S ,%. dea _ '

3.F. Opeka Senior Vice President By: C.F. Sears Vice President (3) W.G. Counsil letter to 3.R. Miller dated March 30,1984, " Millstone Nuclear Power Station Unit I40. 2 Spent Fuel Disposition Plans."

. . BIND Tatto 1 COMPARISON OF MODEL ANO TEST DATA FREQUENCIES Afr/ No. of Tank Model Max. tMin.

Water Rods Wall Freq. Test ~ Test Water Freq. Freq. '

Effects (Mz) (Mz) (Mz)

Air 0 No 45.5 44.9 42.4 Water 0 No 19.7 18.0 17.4 Water 0 Yes 18.4 N/A Air 378 No 11.9 N/A Water 378 No 11.0 10.3 9.5 Water 378 Yes 10.8 10.3 9.5 Table 2

, SUMARY OF FORCED VfBRATION MODEL TEST COMPAR!50N No. 5A Damping Peak CF58 First Model of Input Ratio Base Mid-Pt. Mode Length Rods Disp 1. Reaction (LVOT5) Freq.

Force 01s01.

(in) (1) (1bs) (in) (Mr) (in) a) Test Results 378 .025 3.9 2250 .183 9.5 N/A b) Model Results 378 .025 4.8 1854 .17 10 155.5 378 .025 3.8 2236 .20 10 155.5 378 .025 1.9 4437 40 10 155.5 Notes:

1) The difference in test and model frequency is insignificant since the response is evaluated at resonance. The model fracuency is selected to represent an average of all input disp 1&:e-ents, whereas the test frequency is spectfic for 0.025 inch single amplitude (!A).

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2) The second case in the model results is the comparable case to the test seguence in terms of properties. This case provides a good agreement of test and model results.

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