ML19270H329
| ML19270H329 | |
| Person / Time | |
|---|---|
| Site: | La Crosse File:Dairyland Power Cooperative icon.png |
| Issue date: | 06/21/1979 |
| From: | Linder F DAIRYLAND POWER COOPERATIVE |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| LAC-6349, NUDOCS 7906260212 | |
| Download: ML19270H329 (6) | |
Text
V s
Ib.tIIt YIntNIb I'0 WEIT COGI*EIt.t TIVE Ba 60ue, 0% nan 54601 June 21, 1979 In reply, please refer to LAC-6349 Director of Nuclear Reactor Regulation U.
S.
Nuclear Regulatory Commission Washington, D.
C.
20555
SUBJECT:
DAIRYLAND POWER COOPERATIVE IA CROSSE BOILING WATER REACTOR (LACBWR)
PROVISIONAL OPERATING LICENSE NO. DPR-45 PROPOSED MODIFICATION - SPENT FUEL STORAGE
Reference:
(1)
DPC Letter, LAC-6296, Linder to Director of Nuclear Reactor Regulation, dated May 17, 1979.
Gentlemen:
Our letter, Reference 1, submitted additional information concern-ing the suitability of the boron carbide poison material proposed for the LACBWR high density fuel storage racks.
Upon rereviewing this information, it was determined that corrections contained on pages 3 and 4 are necessary.
We are, therefore, resubmitting revised copies of the attachment to LAC-6296 originally dated 5/17/79.
If there are any questions concerning this, please contact us.
Very truly yours, DAIRYLAND POWER COOPERATIVE q
/
,7 4-(%d,
tkt Frank Linder, General Manager FL:RES:af cc:
(See Attached) 2318 231 7 90626 O k/Z [
Director of Nuclear Reactor Regulation LAC-6349 Washington, D.
C.
20555 June 21, 1979 cc:
J.
G.
Keppler, Regional Director U.
S.
Nuclear Regulatory Commission Directorate of Regulatory Operations Region III 799 Roosevelt Road Glen Ellyn, IL 60137 Charles Bechhoefer, Esq., Chairman Atomic Safety and Licensing Board Panel U.
S.
Nuclear Regulatory Commission Washington, D.
C.
20555 Mr. 7alph S.
Decker Route 4 Box 190D Cambridge, MD 21613 Dr. George C. Anderson Departrent of Oceanography University of Washington Seattle, Washington 98195 O.
S.
Hiestand, Jr.
Attorney at Law Morgan, Lewis & Bockius 1800 M Street, N.
W.
Washington, D.
C.
20036 Kevin P.
Gallen Attorney at Law Morgan, Lewis & Bockius 1800 M Street, N.
W.
Washington, D.
C.
20036 Coulee Region Energy Coalition P.
O.
Box 1583 La Crosse, WI 54601 2318 232 LAC-6296 5/17/79 SUPPLEMENTARY INFORMATION ON THE POISON MIsTERIAL SELECTED FOR THE LACBWR HIGH DENSITY FUEL RACKS PROPOSED MODIFICATION - LACBWR SPENT FUEL STORAGL on January 4, 1979, Dairyland Power Cooperative submitted informa-the B C Composite poison material pro-tion on the suitability of 4
posed for the LACBWR high density fuel storage racks (Ref. DPC Letter LAC-6067).
This information, submitted in response to specific NRC questions regarding the LACBWR fuel racks licensing amendment, was based on the partial results of an extensive test program developed and impelemented by the B C Composite material 4
supplier, the Carborundum Company.
The Test Program was comprised of four parts as follows:
a.
Short Term Test (simultaneous exposure of BgC0 Rads materials, to a gamma radiation level t'
10 and prototypical fuel pool water environments both deionized water and borated water).
b.
Offgassing Test c.
Leachability Test d.
Long Term Test (simultaneous expcsure of B C materials 4
11 Rads and deionized to a gamma radiation level of 10 water).
The results of the first three parts of the Test Program were pre-sented in Carborundum Report CBO-N-78-299 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.
Dairyland Power Cooperative referenced this report in the information previously submitted to NRC.
The Long Term Test has recently been completed by the Carborundum Company.
The results of this part of the Test Program are presented in CBO-N-79-064 (Addendum I, March 1979) which has also been submitted as a proprietary repor c nder Dockets 50-218 and 50-245.
The purpose of the Long Term Test Program was to establish the mechanical and physical behavior of the B C plate and Composite 4
ll Rad gamma and materials for the simultaneous expc'2re up to 10 deionized water.
The mechanical ber vior of the Composite material was assessed by determining the Ult ite Tensile Strength (UTS) 2318 233 1_
LAC-o296 5/17/79 and the Modulus of Elasticity (MOE) values at various exposure levels during the program.
The physical behavior of the Composite material was assessed by visual inspection and by dimensional and 10 loadinc weight determinations at various exposure levels.
The B was meacured by means of destructive chemical analysis on samples exposed to 5 x 10 10, 8 x 10 10 and 10 11 Rad gamma.
Mechanical Properties The response to NRC Question 26e (Ref. DPC Letter LAC-6067) stated that the Composite material would possess adequate strength if the Ultimate Tensile Strength (UTS) value exceeded the specifi.ed to the value of 2200 psi during and after simultaneous exposure design radiation level of 10 11 Rads and prototyoical spent fuel pool water environments.
If the Composite material met the specifi-cation value of 2200 psi, the bending stresses during a SSE event (620 psi) would be less than the SSE tensile strength acceptance criterion (0.32 UTS minimum).
The results of the Long Term Test indicate the composite material exposed to the spent fuel pool water environnent will maintain an Ultimate Tensile Strength in excess of 4500 psi for radiation exposures up to 10 Rad gamma.
It shculd be noted that this value 11 was established for the Composite material tested in a moist cun-dition (See Item 11,Section IV of CBO-N-79-064) and is consistent with the predicted value (4500 psi) presented in Table 1 cf the response to Question 26f.
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 11 considered, the minimum value determined for exposure up to 10 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 1 Rad).
10 to 10 value throughout the Long Term Test Program (from 10 Physical Properties The results of the Lcng Term Test Program indicate tnat the Composite 10 material lost mass as the radiation exposure increased from 10 to Rads gamma.
It was concluded that the material loss was 10 11 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 sampics (pre and post irradiction) indicated that the material was preferentially lost from one side of the Composite material and that the maximum loss 10 Rads gamma (approximately 3 rate occurred between 3 and 5.5 x 10 10 and 1 x 10 11 times greater than the rate observed between 8 x 10 Rads gamma).
2318 234 LAC-6246 5/17/79 Rev. 6/18/79 The Composite material consists of three regionu:
the prirary
.D;"
side which contains the major concentration of B4C naterial, the reinforcing fiber which contains Bac and binder materials in the spaces between the fibers and the back side which contains lesser amounts of D4C and binder material.
The B4C and binder material lost from the Composite material came primarily from the back side.
It has been concluded that this preferential loss occurs because the B C concentration in the back side is only 50? of that in the 4
primary side.
Essentially all radiation effects data show that the radiation resistance of the binder material is greatly enhanced by the addition of mineral filler materials such as B C.
The 4
higher concentration of B4C in the primary side protects the assoc-iated binder material to a greater degree than the lower B4C con-centration in the back side.
This conclusion is supported by the fact that the majority of material loss frca the back side occurred during the exposure range from 3 to 5.5 x 10 10 Rads gamma and that the Ccmposite material exhibited only a modest weight loss, thereafter, from 5.5 x 10 10 lS 11 through 10 Rads exposure.
The principal concerns with the loss of mass are:
- 1) the integrity of the bond between the primary side material and the reinforcing ma terial and 2) the potential effect of the loss of B4C on the Eeff value.
Bond strength of the irradiated material has been tested to demonstrate the integrity of the primary side / reinforcing material bond.
This was done by way of a bend test (samples placed in a vertical ecde are arched repeatedly to stress the bond) and a tape test (primary side of samples are attached to standard tape amount of B C grain adhering to tape and then the tape is removed; 4
measures bond strength).
The results of the test verify that an adequate bond has been maintained.
No tendency of the primary side to separate from the reinforcing material fibers has been observed.
10 concentration The loss of B C has been determined to reduce the B 4
10 ll by 3 w/o at 3 x 10 Rad gamma and by 15 w/o at 10 Rad gamma.
The expected exposure levels for the LACBWR poison material were presented in Response to NRC Quesgion 26b (Ref. DPC Letter LAC-6067).
These levels ranged from 8.4 x 10 Rads gamma fcr freshly discharged fuel stored continuously in the fuel racks for the design life of 1c the racks (25 years) to 2.9 x 10 Rads gamma for stored fuel re-placed every 5 years with freshly discharged fuel over the design life of the racks.
Foy0the conservatively calculated maximum ex-10 posure level (2.9 x 10 Rads), the 3 w/o reduction in B concen-tration has no adverse effect on the LACBWR Keff values as reported in NES BlA0547 for the following reasons:
Tpgpoisonmaterialspecificationreguirestheminimum a.
U 2
B concentration value (0.024 gms B
/cm ) to exist afygr simultaneous exposure to deminerali-ad water and 10 Rads gamma.
2318 235 3-
LAC-6296 5/17/79 Rev. 6/18/79 L.
The B I' concentration used in the criticality analyses 10 2
was 0.022 gms B
/cm,
Even if the maximum reduction in B IO concentration observed in a Rad gamma exposure, (19.2%) is applied Test Program sample for 10 11 1C concentration specified for the LACBWR Composite to the minimum B material (0.024 gm/cm ), the worst case abnormal Keff value in-2 creases from 0.9275 to only 0.9355.
Clearly the Keff value remains S>
significantly below the 0.95 criterion.
It is,therefore, concluded that the Composite material selected for use in the LACBWR high density fuel racks maintains acceptable mechanical and physical properties even after simultaneous exposure to gamma radiation levels of 10 ll Rads and prototypical fuel pool environments.
2318 236