ML20043F028
| ML20043F028 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 06/05/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20043F026 | List: |
| References | |
| NUDOCS 9006140105 | |
| Download: ML20043F028 (2) | |
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FAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENDMENT NO. 123 TO FACILITY OPERATING't.1 CENSE NO. OPR-28:
VFRMONT YAHKEE NUCLEAR POWER CORPORATION VERP0HT YANKEE NUCLEAR POWFP STATION DOCKET NO. 50-271 INTRODUCTION
-(y letter dated February ?8,1990, the Vermont Yankee Nuclear Power Corporation P
the licensee) proposed a change to Technical Specification 5.2 of the Design Features section of the Technical Specifications (TS). The proposed change revises the TS to add hafnium as an alternate absorber material in the
-control blades. This would allow the control blades in the reactor to contain either B t powder or bafnium, or a combination of the two as the control g
material. The reason for this change is that hafnium absorber material can prolong the control blade nuclear lifetime and reduce the number of' discharged blades, thereby_ reducing the on-site storage and handline.
FYAtVATION The staff' discovered in late 1988 that hafnium control rods in some PWRs can swell due to cracking and hydriding. The affected licensees have taken remedial actions to correct this problem, and have implemented surveillance plans. ' Although the staff has not yet observed any similar problem of
' hafnium swelling and cracking in BNPs, we will continue to monitor the hafnium rechanical and ruclear performance in BWRs.
The use of hafnium as an alternative control material in PWRs has been approved in lead test assembly designs. General Electric and t!EA-ATOM have previously used the combinction of hafnium and B C centrol material in control blade f
- designs, in general, hafnium has effdctively shown satisfactory neutronic performance.
The use.of hafnium material minimi:es the problem of intergranular s. tress corrosion cracking (IGSCC) associated with the B C material because hafnium 4
produces lest fission gas and thus less swelling than B C.
Therefore, 4
designers frecuently employ hafnium in the top 6 inches in the outer row of tubes because these areas experience higher neutron flux.
The licensee stated that "For alternative control rod designs, the Limiting Conditions of Operation (LCOs) 3.3.A, 3.3.B. and 3.3.C protect the integrity of the plant. These LCOs provide the minimum shutdown margin, require a shutdown margin demonstration, restrict the contrni rod drop accident impact, cnd specify the average and four-rod group scram times. The impact of utilizing a 9006140105 900603 PDR ADOCK 0500L27i P
,,..e es new control rod design on each of these LCOs as well as the impact en licensing using the approved metnods listed in Specification 6.7.A.4, will
.be verified before installation."
i On the basis of the above considerations the staff concludes that-the use of
~
. hafnium control material and the associated Technical Specification changs are acceptable for_ Vermont Yankee.
ENVIRONMENTAL. CONSIDERATION This amendment involves a change in a requirement with respect to the installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. The staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types,'of any effluents that may be released offsite, and that there is.no-significant increase-in individual or cumulative occupational radiation exposure.
The Commission has previously published a proposed finding'that the amendment involves no significant hazards consideration and-there has been no public coment on such finding. Accordingly, this amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant
-to 10 CFR 51.22(b), no environmental impact statement or environmental I
assessment need be prepared in connection with the issuance of this amendment.
CONCLUSION j
i The Commission made a proposed determination that the amendment involves no i
significant hazards consideration which was published in the Federal-Register
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(55 FR 10546) on March 21, 1990 and consulted with the State of Vermont. No public comments were received and the State of-Vermont did not have any coments.
s The staff has concluded, based on the considerations discussed above, that: '
(1) there is reasonable assurance that the health and safety of the public will not be endangered by operation ir the )roposed manner, and (2) such activities will be conducted in compliance with tie Comission's regulations, and (3) the issuance of this amendment will not be.nimical to the comon defense and security or to the health and safety of the public.
Principal Contributor:
S.L. Wu V. Rooney Dated:
June 5, 1990
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