ML20072L387
| ML20072L387 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 08/24/1994 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20072L377 | List: |
| References | |
| NUDOCS 9408310238 | |
| Download: ML20072L387 (6) | |
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UNITED STATES i '
NUCLEAR REGULATORY COMMISSION
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WASHINGTON, D.C. 2055W1 SAFETY. EVAL 0ATIONBYTHEOFFICEOFNUCLEARREACTORREGULATION RELATED TO AMENDMENT NO.191 TO FACILITY OPERATING LICENSE NO. DPR-53 AND AMENDMENT N0.168 TO FACILITY OPERATING LICENSE NO. DPR-69 BALTIM0RE GAS AND ELECTRIC COMPANY CALVERT CLIFFS NUCLEAR POWER PLANT. UNIT NOS. 1 AND 2 DOCKET NOS. 50-317 AND 50-318
1.0 INTRODUCTION
By letter dated November 3,1993, the Baltimore Gas and Electric Company (BG&E) submitted a request for changes to the Calvert Cliffs Nuclear Power Plant, Unit Nos. I and 2, Technical Specifications (TSs). The requested changes would climinate TSs that are applicable to the incore instrumentation (ICI) system and relocate the limitations on the use of the ICI system to the Calvert Cliffs Updated Final Safety Analysis Report (UFSAR).
The request also would eliminate cycle-specific footnotes which are no longer applicable i
because the cycles have been completed.
In addition, the Table of Contents and TS BASES are modified to reflect the requested changes.
The ICI system at Calvert Cliffs consists of 45 neutron detector strings positioned in the center of selected fuel assemblies.
Each detector string consists of 4 rhodium neutron detector segments located at 20, 40, 60, and 80 percent of core height. The neutron flux indicated by the detector segments is processed by a full-core power distribution system to determine the peak linear heat rate, peak pin power, radial peaking factors, and azimuthal power tilt for comparisen to the TS limits. Thus, the ICI system is directly used to verify core power distribution limits.
These core power distribution limits are important assumptions in the analysis of accidents and transients, but the ICI system itself has no safety function.
Section 50.36 of Title 10 of the Code of Federal Regulations established the regulatory requirements related to the content of TSs.
The rule requires that TSs include items in specific categories, including safety limits, limiting conditions for operation, and surveillance requirements; however, the rule does not specify the particular requirements to be included in the a plant's TSs.
The NRC developed criteria, as described in the " Final Policy Statement on Technical Specification Improvements for Nuclear Power Reactors,"
(58 FR 39132) to determine which of the design conditions and associated surveillances need to be located in the TSs because the requirement is "necessary to obviate the possibility of an abnormal situation or event giving rise to an immediate threat to the public health and safety." Briefly, those criteria are (1) detection of abnormal degradation of the reactor coolant 9408310238 940824 PDR ADOCK 05000317 l
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. pressure boundary, (2) boundary conditions for design basis accidents and transients, (3} primary success paths to prevent or mitigate design basis accidents and transients,'and (4) functions determined to be important to risk or operating experience. The Commission's final policy statement acknowledged that its implementation may result in the relocation of existing TS requirements to licensee controlled documents and programs.
The ICI system is used to verify core power distribution limits which are process variables that are required to be located in the TSs. However, in relation to the four criteria: (1) the ICI system provides no function which would indicate a degradation in the reactor coolant pressure boundary; (2) the proposed change does not eliminate the core power distribution limits from the TSs -- it only relocates the details on how the limits are measured; (3) the ICI system does not function or actuate to mitigate a design basis accident or transient; and (4) operating experience and a plant-specific probabilistic safety assessment performed for Calvert Cliffs indicates that the ICI system does not have a significant impact on public health and safety.
Therefore, the ICI system does not satisfy any of the final policy statement criteria which would necessitate that it be included in the TSs.
2.0 EVALUATION Essentially all pressurized-water reactor TSs contain a requirement for operability of 75 percent of the incore detector locations for mapping of the core power distribution.
Incore detector data is used to calculate power peaking factors which are used to verify compliance with fuel performance limits.
While relocating the ICI system operability requirements is not a concern, the possibility of changing the number and/or distribution requirements is of concern.
l On a number of occasions.
)r various reasons, failures of detector strings in i
operating pressurized wat reactors have approached or exceeded 25 percent, and relaxation of the 75 -
cent requirement has been permitted for the duration of the affected cc eating cycle. This relaxation was justifiable because the reactor had started the cycle and performed the physics startup tests with at least 75 percent of the incore detector locations operable, general trends for the cycle had been established and the system would be restored to full (or nearly full) complement before beginning the next cycle.
In addition, the uncertainties on the measurements was increased to account for fewer operable detectors.
A significant safety concern relating to degradation of incore mapping, as the result of failed incore detectors, is the ability to detect anomalous conditions in the core. One of these is the inadvertent loading of a fuel assembly into an improper position.
Since this is a loading problem, it is of significant concern if long-term operation with fewer than 75 percent of the detectors is considered.
It is not of as much concern when relaxation of requirements is considered for only the remainder of an operating cycle.
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, Currently, TS 3.3.3.2.'a requires at least eight azimuthal power tilt estimates with a minimum'of two estimates of each of the four detector segment axial elevations. This requirement wa( established to ensure adequate core coverage. Changes to this requirement must be carefully reviewed and justification provided to specify how adequate core coverage would be maintained and how anomalies would be detected.
BG&E has indicated that changes to the requirements on number and/or distribution of operable incore detectors will be evaluated utilizing the 10 CFR 50.59," changes, tests, and experiments." The 10 CFR 50.59 process allows (in part) that changes, without prior Commission approval, can be made unless the proposed changes involve a change to the TSs incorporated in the license or result in an unreviewed safety question.
In order to change the requirements concerning the number and location of operable detectors a rigorous evaluation and justification is required. The following considerations must be included in a 10 CFR 50.59 evaluation if changes to the requirements for the ICI system are proposed:
1.
How an inadvertent loading of a fuel assembly into an improper location will be detected, 2.
how the validity of the tilt estimates will be ensured, 3.
how adequate core coverage will be maintained, 4.
a list of the measurement uncertainties and why the added uncertainties are adequate to guarantee that measured peak linear heat rates, peak pin powers radial peaking factors, and azimuthal power tilts will meet TS limits, and 5.
the ICI system will be restored to at least 75 percent prior to the beginning of a new cycle.
Based on the above, the staff concludes that the ICI system does not need to be controlled by TSs, and that changes to the ICI system can be adequately controlled by the 10 CFR 50.59 process.
Should the licensee determine that an unreviewed safety question is involved, due to either (1) an increase in the' probability or consequences of accidents or malfunctions of equipment important to safety, (2) the creation of a possibility for an accident or malfunction of a different type than any evaluated previously, or (3) a reduction in the margin of safety, NRC approval and a license amendment would
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be required prior to implementation of the change. NRC inspection and enforcement programs also enable the staff to monitor facility changes and licensee adherence to the UFSAR commitments and to take any remedial action that may be appropriate.
The staff further concludes, that the removal of the cycle-specific footnotes is acceptable, in that the cycles have been completed, and that the Table of Contents and TS BASES be changed to reflect these changes.
. 3.0 TECHNICAL SPECIFICATION CHANGEji TSs 3.2.1., 3.2.2.1, and 3.2.3 - 1emove cycle-specific footnotes.
These footnotes are no longer needed because the specific cycles are completed.
Section 3.3.3.2 - This section will be eliminated and the limitations on the use of the ICI system, including the number of required detectors and their distribution, will be relocated to the UFSAR.
Surveillance 4.2.1.4.b - Remove the uncertainty factors applied to the ICI system and relocate them to the UFSAR.
The Table of Contents and TS BASES are modified to reflect the above changes.
4.0
SUMMARY
Based on the staff's evaluation in Section 2.0 above, the staff concludes that the proposed TS changes noted in Section 3 above are acceptable.
The relocation of the ICI system requirements to the UFSAR is acceptable because (1) its inclusion in the TSs is not specifically required by 10 CFR 50.36 or other regulations, (2) the ICI system requirements have been relocated to the UFSAR and are adequately controlled by 10 CFR 50.59, (3) its inclusion in the TSs is not required to avert an immediate threat to the public health and safety, and (4) changes that are deemed to involve an unreviewed safety question require prior NRC approval in accordance with 10 CFR 50.59(c).
However, changes to the number and distribution of incore detectors necessary to measure the core power distribution limits require rigorous evaluation and justification as detailed in Section 2 above.
The staff would like to further emphasize that it would be prudent to restore the ICI system to a full or nearly full compliment of detectors at the beginning of each cycle.
5.0 STATE CONSULTATION
In accordance with the Commission's regulations, the Maryland State official was notified of the proposed issuance of the amendments.
The State official had no comments.
6.0 ENVIRONMENTAL CONSIDERATION
The amendments change a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20 and changes to surveillance requirements.
The NRC staff has determined that the amendments involve 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 issued a proposed finding that the amendments involve no significant hazards consideration, and there has been no public comment on such finding (56 FR 64601). Accordingly, the amendments meet 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 assessment need be prepared in connection with the fssuance of the amendments.
7.0 CONCLUSION
The Commission 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 in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.
Principal Contributor:
M. Chatterton Date: August 24, 1994
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Mr. Robert E. Denton August 24, 1994 l
A copy of the related ~ Safety Evaluation is enclosed. A Notice of Issuance will be included-in the Commission's next regular biweekly Federal. Reaister notice.
Sincerely, ORIGINAL SIGNED BYi Daniel G. Mcdonald, Senior Project Manager i
Project Directorate I-l i
Division of Reactor Projects - I/II Office of Nuclear Reactor Regulation
Enclosures:
1.
Amendment No.191 to DPR-53 2.
Amendment No.168 to DPR-69 3.
Safety Evaluation cc w/ enclosures:
Distribution:
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OFFICIAL RECORD COPY FILENAME: CC88166.AMD l
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