ML20204G487
| ML20204G487 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 10/17/1988 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20204G458 | List: |
| References | |
| NUDOCS 8810240134 | |
| Download: ML20204G487 (3) | |
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NUC' EAR REGULATORY COMMISSION s
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR RC;ULATION SUPPORTIllG AMENDMENT fl0. 118 TO FACILITY OPERATIllG LICENSE NO. OPR-3 YANKEE ATOMIC ELECTRIC COMPANY YANKEE NUCLEAR POWER STATION DOCKET NO.50-029 INTRODUCTION By letter dated August 11, 1988, Yankee Atomic Electric Corpany (YAEC or the i
licensee) submitted a request for changes to the Yankee Nuclear Power Station (YNPS or the plant) Technical Specifications (TS).
1 The amendment rr. coves a reference to a specific value of 2,200 ppm and i
provides a generalized boron concentratier, value in its place.
In addition, TS 4.9.1.1.c, which requires an inverse count rate multiplir.ation measurement i
to be performed at least after the insertion of each five fuel assemblies, is l
deleted.
EVALUATION i
The reason for the change of the 2,200 ppm value to a generalized boron concentration value sufficient to meet the shutdown margin requirement in Mode 6 is administrative. The boron concentration value needed to maintain sufficient shutdown margin during refueling is in cixcess of 2,200 ppe. The wording change in Action Statement 3.9.1.a to a bcron concentration value sufficient to ensure a k-effective of less than 0.93 provides consistent
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terminology with the Limiting Cundition for Operation (LCO) as specified in i
The removal of Surveillance Requirement 4.9.1.1.c is proposed to eliminate an unnecessary surveillance when other surveillance requirements are present to ensure sufficient shutdown margin is available, and inadvertent criticality is precludede i
Yerification of the boron concentration in Mode 6 provides adequate control that sufficient shutdown margin is maintained.
Surveillance of the boron concentration is the means of the shutdown margin verification in the Standard Technical Specifications during Mode 6 operation, as well as in the other operating modes at the YMPS. Periodic surveillance of the boron concentration during refueling operations is required by TS 4.9.1.3.
Boron concentration surveillance is a more directly observable and more accurate indication of shutdown margin than the inverse count rate multiplication measurement at highly subtritical reactor conditions.
There is more uncertainty in the inverse multiplication neasurement due to changes in the j
source-fuel-detector geometry during core loading which generally produces a
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scattering of the measured data, j
8810240134 8s1017 PDR ADOCK 05000027 P
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Technical Specification 4.9.1.1.c is not needed to preclude inadvertent criticality as other means are present for that purpose.
These include the following:
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Technical Specification 4.9.1.2 which requires equipment which would make possible inadvertent reactivity increases to be made inoperable and tagged out of service.
2.
Technical Specification 4.9.1.5 which requires a record of the neutror.
count rate before and after any change in core geometry.
3.
Technical Specification 3.9.1, Action Statement b, which requires that with a significant unexpected increase in the count rate on any channel i
or an unexpected increase in the count rate by a factor of two after i
adJition of a new fuel assembly or removal of a control rod to suspend core alterations until the situation is reviewed by plant technical supervisory personnel.
l In addition, during fuel movement when the shield tank cavit assumed shutdown margin for a boron dilution event is 5.0% (y is filled, the as noted in the YNPS Core 19 Performance Analysis, January 1987), when in fact the actual refueling boron concentration is calculated based on the freshly loaded core l
with a k-effective of 0.93 and the most worthy control rod stuck out of the i
core. A 1.0% reactivity uncertainty is also applied to the calculated i
value. Therefore, inadvertent criticality during Mode 6 due to boron i
dilution is extremely unlikely given the large subcritical margin during fuel i
movements, j
The NRC in License Amendment No. 69, issued on July 21, 1981, evaluated, among other concerns, boron dilution eve Ms in Mode 6.
We concluded that due to the redundant and diverse instruments and alarms. "... the plant is adequately protected for postulated dilution events in all modes assuming the worst single active failure." Based on the above considerations, we conclude that the changes to TS 3.9.1.a and removal of TS 4.9.1.1.c are acceptable.
ENVIRONMENTAL CONSIDERATION This amendment involves a change to a requirement with respect to the instal-lation or use of facility components located within the restricted ar(a as J
defined in 10 CFR Part 20.
The staff has determined that the amendment involves no significant increase in the amounts, and no signift: ant change in the types, of any effluents that may be released offsite and that there is no
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significant increase in individual or cumulative occupational radiation exposure. The Comission has previously issued a proposed finding that this amendment involves r.o significant hazards consideration and there has been no public ccament on such finding. Accordingly, this amendment meets the eligi-bility 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 assessment need be preparrd in connection with the issuance of this amendment.
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. l CONCLUSION i
The staff has concluded, based on the considerations discussed above, that:
(1) there is reasonable assurance that the health and safety of the will not be endangered by operation in the proposed manner, and (2) public such activities will be conducted in compliance with the ;ommission's regulations and the issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
l ACKNOWLEDGEMENT l
Principal Contributor: Morton B. Fairtile Dated: October 17,1988 t
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