ML19246A566
| ML19246A566 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 06/27/1979 |
| From: | Moore G FLORIDA POWER CORP. |
| To: | Reid R Office of Nuclear Reactor Regulation |
| References | |
| 790629, NUDOCS 7907030377 | |
| Download: ML19246A566 (5) | |
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Florida Power June 29, 1979 Mr. Robert W.
Reid Chief Operating Reactors Branch #4 Division of Operating Reactors U. S.
Nuclear Regulatory Commission Washington, DC 20555
Subject:
Crystal River Unit 3 Docket No. 50-302 Operating License No. DPR-72 High Density Fuel Racks
Dear Mr. Reid:
In our letter of March 16, 1979, Florida Power Corporation submitted infor-mation on the suitability of the B4C Composite poison material proposed for the Crystal River high density fuel storage racks.
This information, cub-mitted in response to specific NRC questions regarding the Crystal River fuel rack licensing amendment, was based on the pa r t ia l resulte of an extensive test program developed and implemented by the B4C Composite material supplier, the Carborundum Company.
The Test Program was comprised of four parts as follows:
a.
Short Te rm Test (simultaneous exposure of B4C mater-tals, to a gamma radiation level of 1010 Rads and prototypical fuel pool water environments both deion-ized water aad borated water).
b.
Offgassing Test.
c.
Leachability Test.
d.
Long Term Test (simultaneous exposure of B4C materials
,9 ~ O to a gamma radiation level of 1011 Rads and deionized
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7 9 0 7 0 3 0 3'q The results of the first three parts of the Test Prodram were presented in Carborundum Report CBO-N-73-299 which was submitted as a proprietary report by the Connecticut Yankee Power Company under Docket 50-218 and the Northeast Nuclear Energy Company under Docket 50-245.
Florida Power Co r-poration referenced this report in the information previously submitted to NRC.
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Petersbu g F'ordi 33?33 e 813 - Elf > 515' General Office 3201 ineHouen sneet scum. P O Bon 14042. St r
Mrm Robert W.
Reid Page Two June 29, 1979 T1 Long Term Test has recently been completed by the Carborundum Company.
The results of this part of the Test Proi; ram are presented in CBO-N-79-064
( Addendum A, March 1979) whici has also been submitted as a proprietary re-port under Dockets 50-218 and 50 245.
The purpose of the Long Term Test Program was to establish the mechanical and physical bchavior of the B4C plates and Composite materials for simul-taneous exposure up to 1011 Rad gamma and deionized water.
The mechanical behavior of the material was assessed by determining the Ultimate Tensile Strength (UTS) and the Modulus of Elasticity (MOE) values at va r io us expo-sure levels during the program.
The physical behavior of the ma te r1J wa s assessed by visual inspection and by dimensional and weight determinations at various exposure levels.
The BIO loading was measured bv ceans of de-structive chemical analysis on samples exposed to 5 x 1010, 8 x 1010, 1011 Rad gamma.
Mechanical Properties The response to NRC Question A6 of Enclosure 2, Request for Additional In-f<rmation, stated that the Comp 3 site material would possess adequate strength if the Ultimate Tensile Strength (UTS) va lue exceeded the speci-fled value of 2200 psi during and af ter simultaneous expo su re to the design radiation level of 1011 Rads an. pro:otypical spent fuel pool wa te r envi-ronments.
If the Composite material met the specification value of 2200 psi, the actual safety factor cons ering the bending stresses during a SSE event would be in excess of 40.
The results of the Long Term Test indicate the Composite r:ute rial exposed to the spent fuel pool water environment will maintain an Ultimate Tensile Strength in excess of 4500 psi for radiation exposutes up to 1011 Rad gam-ma.
This value is consistent with t he predicted value (4500 psi) presented in Table 1 of the response to Question A6 of Enclosure 2.
It should be noted that this value (4500 psi) was established for Composite material tested in a moist condition (see Item 111, Section IV-li, Addendum A).
Even if the UTS values associated with samples dried for 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> at 105 C (for weight determinations) are considered, the minimum va lue determined for exposure up to 1011 Rad was 2757 psi.
This value is still greater than the minimum specified value (2200 psi).
The Modulus of elasticity value exhibits essentially no change in value 10 Il througnout the Long Term Test Program (from IC to 10 Rad).
Physical Properties 7F 'i The results of the Long Term Test Program icdicate that the composite material lost mass as the rad ia t ion exposure increased from 1010 to 1011 Rads gamma.
It was concluded that the material loss was essentially dose related (less than 2 w/o is attributed to immersion in the deionized water) and primarily a surface phenomenon.
Visual and micrographic examination of the Composite test samples (pre-and post-irradiation) indicated that the material was preferentially lost from one side of the Composite ma te rial b
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Mr. Robert W.
Reid Page Three June 29, 1979 and that the maximum loss rate occurred between 3 and
- 5. 5 x 1010 p,
gamma approximately 3 times greater than the rate observed between 8 x 101 11 and I x 10 Rads gamma).
The Composite material consists of three region ; the primary side which contains the major concentration of B4C material, the reinforcing fiber which contains B4C and binder materials in the spaces be tween the fibers and the back side which contains lesser amounts of B4C and binder materi-al.
The B4C and binder materia] lost from the Composite material came primarily from the back side.
It has been concluded that this pteferential loss occurs because the B4C concentration in the back side is only 50% of that in the prtmary side.
Essentially, all radiation effects data s:.a that the radiat5 an resistance of the binder material is greatly ceanced by the mia! tion of mineral filler materials such as B4C.
The higher concen-tration af B4C in the primary side prote a; the asecciatM M naar mrcrial to a greater degree than the lower B4C concentration in the back side.
This conclusion is supported by the fact that the majority of material lost from the back side c: curred during the exposure range frou 3 to 5.5 x 1010_
Rads gamma and that the composite material exhibited only a modest weight 11 10 loss, thereafter, from 5.5 x 10 through 10 Rads exposure.
The principal concerns with the loss of mass are, 1) the integrity of the bond between the main coat material and the reinfercing material and 2) the potential effect of the loss of B4C on the keff value.
Bond strength of t he irradiated material has been tested to demonstrate the integrity of the main coat / reinforcing material bond.
This was done by way of a bend test (samples placed in a vertical mode are arched repeatedly to stress the bond) and a tape test (primary side of samples are attached to standaru tape and then the ta pe is removed: amount of B4C grain adhering in tap.
measures bond st rength).
The results of the test verify that an adequate bond has been maintained.
No tendency of the main coat to separate from the reinforcing meterial fibers has been observed.
With respect to the effect on kegg value, the loss of B4C has been deter-10 mined to reduce the B concentration by 15%.
The Composite material 10 manufactured for Crystal River has an ave rage B concentration of 0.0150 gm B10 2
/cm as determined by chemical analysis of random samples.
10 A lying the 15% reduction in B concentration to this value produced a B
concentration of 0.01275 gas.
B10 2
/cm which is still greater than the minimum concentration value used to establish the keff values in the Criti-cality Analysis (0.012 gm B10 2
/cm ).
Consequently, the worst case abnormal kerg value is expected to remain below the value reported in NES 81A0521 (0.9356).
Even if the maximum reduction in B10 concentration observed in 10 any single Test Program sinple (19.2%) is applied to the minimum B con-centration estallished for the Crystal River Composite production material (0.0125 gms B10feg2), the worst case abnormal keff value increases from 0.9356 to only 0.9390.
Clearly, the keff value remains significantly below the 0.95 criterion.
?
Mr. Robert W.
Reid Page Four June 29, 1979 It is, therefore, concluded the Composite material selected f or use in the Crystal River high density fuel racks mainta ins acceptable.rechanical and physical properties af ter simultaneous exposure to gamma radiation levels of 1011 Rads and prototypical fuel pool environments.
As a result of Florida Power Corporation's past responses to NRC Questions /
Concerns, and along with the additional information provided in this let-ter, we are confident that a ll issues can be resolved and we are, there-fore, presently preparing for the installation of high density spent fuel storage racks at CRl/ 3.
The preparation and installation of these racks will be in 4 phases, as identifind in our le t te r to ycu dated Fbrch 16, 1979 (Enclosure 1, Response 1).
The approximate date for the beginning and ending of each Phase is provided below.
Phase Begin End 1
- Decontamination of Pool A June July II - Rack Removal Aug. - Sept.
Oct.
IIi - Rack Disposal Undetermined at this time.
IV - Installation of High Density Racks and Clean-up Activities Nov.
Feb.
In order to ceet the above schedule it was necessary for FPC to authorize fabrication of these high density racks prior to receiving NRC approval.
This submittal completes our response to your concerns regarding the use of the poison material manufactured by Carborundum Company and we would, therefore, li ke to discuss any of our submittals your s ta f f deems neces-sary, in order that NRC approval of our modification can be achieved in a time frame consistent with resolution of the generic licensing issucs and the above schedule.
Please contact this office if you, or members of your staff require addi-tional information concerning this subject.
It is imperative that this modification be complercd prior to the next refueling outage to ensure ade-quate storage capacity is available for all modes of operation.
Very truly yours,
FLORIDA POWER CORPRATION
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G.
C. Moore Assistant Vice President Power Production f.
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STATE OF FLOPIDA COUNTY OF PINELLAS G.
C. Floore states that he is the Assistant Vice President, Power Production. of Florida Pcwer Corporation; that he is authorized on the part of said company to sign and fil,
_th the Nuclear Regulatory Commission the information attached hereto; and that all such statements made and matters set forth therein are true and correct to the best of his knowledge, inf ormation and belief.
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?!oore Subscribed and sworn to before me, a Notary Public in and for the State and County above named, this 29th day of liay, 1979.
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Notary lhykfic Notary Public, State of Florida at Large, fly Commission Expires:
July 25, 1980
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(CRPNotary 1 D12) k