NRC-90-0126, Application for Amend to License NPF-43,revising Tech Spec 5.3.2 Re Control Rod Assemblies.Approval Requested Prior to Second Refueling Outage Scheduled for Mar 1991.Proprietary GE Rept on Control Rod Encl.Rept Withheld (Ref 10CFR2.790)

Application for Amend to License NPF-43,revising Tech Spec 5.3.2 Re Control Rod Assemblies.Approval Requested Prior to Second Refueling Outage Scheduled for Mar 1991.Proprietary GE Rept on Control Rod Encl.Rept Withheld (Ref 10CFR2.790)

ML20058M969
Person / Time
Site:	Fermi
Issue date:	08/01/1990
From:	Orser W DETROIT EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML19298E388	List: ML20058M979 NRC-90-0126, Application for Amend to License NPF-43,revising Tech Spec 5.3.2 Re Control Rod Assemblies.Approval Requested Prior to Second Refueling Outage Scheduled for Mar 1991.Proprietary GE Rept on Control Rod Encl.Rept Withheld (Ref 10CFR2.790)
References
CON-NRC-90-0126 NUDOCS 9008130145
Download: ML20058M969 (9)

Text

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DetTOlt v. m ca.:

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August 1,.1990 100-90-0126 i

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U. S. !belear Regulatory Commission  :

Attn Document Control Desk '

Washington, D. C. N555

References:

1) Permi 2 t 11C Docket No. 50-341 ,

l MC License No. WF-43

2) General Electric Topical Peport, NEDE-22290-A " Safety i Evaluation Of The General Electric Hybrid I Control  !

Rod Assenbly", Septenber,1983

3) General Electric Topical Report NEDE-22290-A, Supplenent 1 " Safety Evaluation Of The General Electric Hybrid I Control Rod Assenbly For The BWR ,

4/5 C Lattice", July, 1985

4) General Electric Topical' Report NEDE-22290-A, Supplenent 2 ' Safety Evaluation of the General l Electric Advanced Longer Life Control Rod Ascenbly," '

i August, 1985 E 5) General Electric Topical Report NEDE-22290-P-A, Supplenent 3 " Safety Evaluation of the General Electric Duralife 230 Control Rod Assenbly",

May, 1988

Subject:

Proposed 'hchnical Specification Change (License i' Anendnent) - 5.3.2 " Control Rod Assemblies" L

Pursuant to 10CFR50.90, Detroit Edison Conpany hereby proposes to anend Operating License WF-43 for the Fermi 2 plant by incorporating the enclosed (Ehclosure 1) change into the Plant 'Nchnical Specifications. The proposed change revises the description of control rod assenblies to a3 dress the use of hafnium as a neutron i absorber material.

We are requesting your review and approval of this proposal prior to '

our second refueling outage which is currently sche 3uled for March, 1991. ,

Enclosure 2 provides General Electric's Duralife 140 and 215 Control Rod Safety Evaluations for Fermi 2. These evaluations are considered I

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August 1, 1990 N}C-90-0126 Page 2 by General Electsic to be proprietary infornation. Delosure 3 provides General Electric's affidavit to that effect. In accordance with 10CFR2.790, it is tequested that Enclosure 2 be withheld from public dinclosure.

Detroit Edison has evaluated the proposed 'Achnical Specification against the criteria of 10CFR50.92 and determined that no significant hazards consideration is involved. The Fermi 2 Onsite Review Organization has @ proved and the Nuclear Safety Review Group has reviewed the proposed Technical Specification and concurs with the enclosed determinations. In accordance with 10CFR50.91, Detroit-B:lison has provided a copy of this letter to tha State of Michigan.

If you have any questions, please contact Mr. Gordon Naier at (313) 586-4513. .

Sincerely, Enclosures cc A. B. Davis R. W. DeFayette W. G. Rogers-J. F. Stang Supervisor, Electric Operators, Michigan Public Service Caraission - J. Padgett

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• USN1C August 1, 1990 MC-90-0126 Page 3 I, WILLIAM S. ORSER, do hereby affirm that the foregoing statenents are based on facts and circunstances which are true and accurate to the best of ory knowledge and belief.

WILLIN4 S. ORSER Senior Vice President On this __ / [- day of (A s0M . 1990, before ne persona 11y' appeared William S. Orser,(heing first duly sworn and says that he executed the foregoing as his free act and deed.

' d/YM Notary Public '

ROSA'!E A ARMETTA Notory Publ'c, h8avoo Ccung M WcommlukmEWuJon.11.1992 4

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4 DCLOSURE 1 PRCPOSED TBCIMCAL SPECIFICATION CHANGE

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Enclosure to C . NRC-90-0126

• Page 1 liffRODUCTION During Fermi 2's first refueling outage 20 of 185 control rods were replaced as part of Detroit Edison's Cobalt Reduction Proa, ram. The replacement control rods were of the same design as the control rods -

they replaced except that they were refurbished to contain pins and rollers free _from cobalt alloy material. All of Fermi 2's original control rods contained Haynes-25 pins and Stellite-3 rollers. Once these materials are irradiated they become a significant source of Co-60 and manrea exposure. As a continuation of Detroit Edison's Cobalt Reduction Program, we are planning to replace the remaining control roda (165) with control rods that contain pins and rollers- i free of. Cobalt alloy material and have their sheathing material made of a stainless steel which has a lower cobalt impw ty level than the original control rods. Replacement of these rods in expected to be performed at the second refueling outage which is currently scheduled for March 1991, It has been estimated that replacing the original control rods will significantly reduce the in-plant radiation levels from crud deposited on pipes, valves, pumps, heat exchangers, etc.

This in turn will greatly reduce our overall aanres exposures since' 70-90% of BWR overall exposures has been found to originate from the plate-out of Co-60.

The 165 remaining replacement control rods will be composed of two designs.that are different from the original. control rods. The neutron absorber material of the original control rods consists of stainless steel tubes filled with boron. carbide, B4C. In addition to.the above sentioned pins,' rollers and sheath material differences, the neutron absorber material of the 165 remaining replacerant control rods consists of stainless steel tubes filled with boron-oGolde and a hafnium plate at the top of the control rod's wing. Replacement control rods that will be used in the control cell core locations and' other selected locations will also contain harnium strips at the outer edge of each uing as a neutron absorber material. The Technical Specifications (TSs) currently only specify boron carbide as a neutron absorber asterial not hafnius. Thus, the purpose of this proposal is to change TS 5 3 2 "CowTaol ROD ASSEMBLIES" to reflect the use of hafnium as a neutron absorber material.

ETALU# TION The proposed TS change has been worded to address the use of hr.fnium as an absorber material in Feral 2 control rods. The existing TS describes the design of control rods in general terms which were vidalf used at the time of Ferai 2's initial licensing. Subsequent to initial licensing n6w control rod designs have been introduced, reviewed and accepted by the NRC, and are in use at many ope . ting

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Enclosure to NRC-90-0126 Page 2 nuclear facilities. The newer designs have many advantages over'the original design such as increased neutron absorber material, improved resistance to intergranular stress corrosion cracking, elimination of structural crevices, lighter coupling / velocity lialter, and reduction of cobalt-bearing material. Additiona cy, the use of hafnium in high flux regions of a control rod has been demonstrated to significantly-increase a rod's nuclear lifetime.

Detroit Edison int %as to replace 165 control rods with two new '

General Electr E control rod designs which incorporate many of the

- above enhanr%sents. The new control rod configurations are C

interchangeable with the existing control rod assemblies and compatable with existing hardware. The NRC has reviewed the new features used in these control rods and found them acceptable. Since both of these new designs utilize hafnium plates and/or strips as previously described, TS 5 3 2 must be revised to address the use of l hafnium.

'Ihe use of control rods containing hafnium does not significantly I change the neutronic or mechanical characteristics of the control rod. References 2'through 5 describe the design features of the i replacement control rods which use hafnlus and have been approved by the MRC. The primary reason for choosing hafnium as a partial substitute for boron-carbide is that it is neutronically similar to boron-carbide. The use of hafnium as a neutron absorber material in control rods has the following characteristics:

a) Reactivity life of hafnium is longer than boron-carbide, because it transmutes to other high absorption cross section isotopes. ,

b) Since transmutation products are hafnium isotopes, there is no  :'

swelling as in boron-carbide.

c) Metallic hafnium does not crack and relocate like boron-carbide ceraalc.

d) Physical properties and structure are scod (similar in many respotstozirconium),particularlythemeltindpoint(only 100 C below boron-carbide).

l e) Mechanical properties are excellent. ,

f) Corrosion resistance is better than Zircaloy.-

g) Chemical compatibility with other reactor materials is good.

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Enclosure to NRC-90-0126

.. Page 3 Control rods which use hafnium are currently in use in many Boiling Water Reactors (BWRs). General Electric control rods which contain hafnium plates at the top of each wing have been NRC approved and used at nine plants. Control rods which contain hafnium on the edge of each wing have been NRC approved and used at 17 plants.

For BWRs the disadvantages of using hafnium, besides tho extra expense, are an increase control rod weight and a slightly lower initial worth than boron-carbide. However, both of these disedvantages have been compensated for in the control rod design. In some of the new control rod designs, these disadvantages are so small that the new designs do not need te specifically address them.

The proposed TS wording (see attached) describes the general design features of the replacement control rods and the twenty refurbished control rods. Please note that the proposed TS wording, as well as the existing wording, is general in nature which could apply to numerous control rod designs. However, the use of any new control rod design is contingent upon satisfactory results of a plant specific safety evaluation in accordance with 10CFR50 59 or NRC approval of the design prior to use in the reactor. Please find attached for your information (see Enclosure 2) General Electric's safety evaluations for the new replacement control rods which we intend to use during our next operating cycle (Cyc'.e 3). (Te assist you in reviewing this information please note that Fermi 2 control rods are designed to the "C" Lattice configuration.) Detroit Edison is finalizing the review of these control rods and performing a plant specific safety evaluation on these designs.

The specific length of the stainless steel tubes containing boron carbide has not been specified in the proposed TS because the length of these tubes varies between control rod designs. Some control rod designs which utilize hafnium as a neutron absorber material have a hafnium plate at the top of each control rod wing. This reduces the length of the stainless steel tubes which contain the boron carbide.

Thus, a specific tube length has not been specified in order to accommodate different control rod designs.

Verification of control rod performance is required per the TSs. TS 4.1.1 " Shutdown Margin" requires that a demonstration test be performed prior to or during the first reactor startup arcer each refueling. Successful completion of this test ensure. that li the reactor can be made subcritical from all operating conditions, 2) the reactivity transients associated with postulated accident conditions are controllable within acceptable limits and 3) the reactor will Se maintained sufficiently suboritical to preclude inadvertent criticality in the shutdown condition. Additionally, TSs 4.1 3 2, T

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Enclosure to NRC-90-0126

. Page 4 4.1 3 3 and 4.1 3 4 ensure control rod scram insertion times are consistent with the times used in the safety analyses. Therefore, in .

addition to the control rod design, the control rods are tested to j onsure that they will perform as expected. {

In suasary, the use of control rods containing hafnium does not '

significantly change the neutronic or mechanical characteristics of the control rod. "he use of hafnium as a neutron absorber material I has been previously reviewed and accepted by the NRC and is currently used in many operating BWRs.

NO SIGNIF" fMT HAZARDS CONSIDERATION In accordance t 'n 10CFR50.92, Detroit Edison has made a determination that the proposed amendment involves no significant hazards I considerations. To make this determination, Detroit Edison aust establish that operation in accordance with the proposed amendaent would not: 1) involve a significant increase in the probability or -

consequences of an accident previously evaluated, or'2) create the possibility of a new or different kind of accident from any accident ,

previously evaluated, or 3) involve a significant reduction in a i nargin of safety, j

1) The proposed change will not involve a significant increase in the prc;, ability or consequences of an acuident previously evaluated beccuse the use of hafnium in control rods as a neutron absorber material does not significantly alter the neutronic or mechanical functional characteristics of the control rods. Since I control rods which utilize harnium have a 1&ger lifetime the  !

probability of some accidents involving the handling, on-site {

storage, and shipping of irradiated rods will actually be reduced.

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2) The proposed change will not ceate the possibility of a new or I

different kinf of accident from any accident previously evaluated because the use of hafnium in control rods as a heutron absorber material does not significantly alter the neutronic or mechanical functional characteristics of the control rods.

The proposed change will not involve a significant reduction in a

3) }

margin of safety because the use of hafnium in control rods as a i neutron absorber material does not significantly alter the )

neutronic or hechanical functional characteristics of the control '

rods. Control rod designs which u6e hafnium have been successfully used in other BWRs, l

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NRC-90-0126.

-r . Page.5l v Based on the above, Detroit Edison has determined that-the proposed-

. amendment does not involve's significant hazards consideration.

z N , gNVIRONMENTAL IMPACT.

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j? L . Detroit Edison has reviewed the proposed Technical Specification-change against the criteria of 10CFR51.22 for environmental e considerations. .The proposed change does not involve a significant' ]

hazards consideration, nor significantly change the types or j F significantly. increase the amounts'of effluents that may be_ released l'

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offsite, nor significantly increase individual or. cumulative s occupationali radiation exposures. Based on the foregoing,= Detroit

- Edison concludesLthat the-proposed Technical Specification'does meet

- the criteria given-in 10CFR51.22(c)(9) for a categorical exclusion

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- fros' the requirements for an Environmental Impact Statement. l CONCLUSION Based on th6 evaluation above: 1) there is reasonable assurance that the health and safety.of the public will not be endangered by operation in the proposed manner, and 2) such activities'will be 4

conducted in compliance with the Commission's regulations'and proposed amendments will not be inimical to the common defense and security or ' ,

to' the health and safety of the public. -

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