ML17139D170
| ML17139D170 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 09/04/1985 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17139D169 | List: |
| References | |
| NUDOCS 8509100060 | |
| Download: ML17139D170 (5) | |
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NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 SAFETY EVALUATION AMEND EN
~ 16 NPF-22 SUS UEHANN STEAM ELECTRIC S ATiON, UNIT 2 DOCKET N
5 -388 Introduction By letter dated April 9, 1985, from B. Kenyon of Pennsylvania Power
& Light Company (PLEL) to A. Schwencer, NRC, the licensee requested Technical Specifi-cation changes for Susquehanna Steam Electric Station Unit 2 (SSES-2).
These changes are related to the required use and operability of the Source Range Monitors (SRM) during reloading (or unloading) of the entire core.
The requested Technical Specification changes for SSES-2 actually take the form of removing the SRH minimum count rate operability requirement when there are eight or fewer fuel assemblies in the reactor.
Evaluation During reload operations the Technical Specifications require minimum count rate levels to be met in order to meet the operability requirement for the SRHs.
In the case of SSES this is 0.7 counts/second with a signal to noise ratio of at least 2.
During reload operations in a Bl<R in which the entire core is
- unloaded, there may be times, when too few fuel assemblies are in the core, to meet the m',nimum count rate necessary to get a reading from the SRMs.
For this condition, other monitors, Fuel Loading Chambers (FLCs), usually called "dunking chambers,"
which can be moved from place to place in the core as loading
- proceeds, are used as a replacement for the SRHs.
Some utilities have found that the FLCs are an impediment to operations.
The licensee has stated that during the SSES Unit I end-of-cycle defueling, the FLCs, which were being used to provide neutron monitoring, produced anomalous readings which were attributed to detector saturation caused by the high gamma flux existing from the irradiated fuel.
PPEL will be offloading the entire core for the upcoming Unit 2 refueling outage and as a result is expecting to experience the same problem.
During the past several years several other utilities have requested Technical Specification changes to permit loading operations such that the use of FLCs can be avoided.
An example being the most recently approved Technical Specification revision for Browns Ferry.
The loading operation for full core reloads involving irradiated fuel may begin without minimum count rates for the SRH for a limited number of assembly loadings (determined to be subcritical).
These loadings place irradiated fuel adjacent to SRM locations.
This provides sufficient neutron sources (e.g.
from gamma-neutron reactions) to meet the Technical Specification minimum SRH count rate requirements.
After the SRHs are thus fully operational the loading proceeds in the usual manner, (e.g.,
spiral loading from the center for Browns Ferry).
PPKL proposes (for full core reloads with irradiated fuel as part of the reload) to begin the reload by first inserting 8 irradiated assemblies (into a fully controlled core).
There will be 2 assemblies adjacent to each of the four SRHs.
The SRHs are in a square array 6 control cells apart.
This 8SO9>00060 850904 PDR ADQCK 05000388 P
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h proposed method is expected to provide the required SRN count rate of 0.7 counts/second with a 2 to I source/noise ratio.
If the count rate is not reached the FLCs will be used as a backup.
The licensee determined that the 8 assemblies in a maximized state with a clustered, uncontrolled configuration would be subcritical and that there would be no possibility of reaching criticality during the loading around the SRNs.
Based on calculations previously seen by the staff these subcriticality results are acceptable.
The actual conditions are controlled (all rods in).
The 4
separate regions of 2 assemblies do not interact making actual conditions far more subcritical than the calculated results show.
Loading patterns to be used following the first 0 assemblies are selected to maintain a continuous multiplying medium between the operating SRN and the loading region to enhance the response of the SRN to the loading changes.
During unloading the last fuel to be removed will be adjacent to the SRYs.
Except for the SRN count rate during the first (last) 8 assembly loading (unloading), all normal limits and control interlocks will be in effect at all times.
The licensee has requested Technical Specification changes to implement this procedure.
The changes affect Table 3.3.6-1 (Control Rod Block Instrumentation) in a footnote to the SRM down-scale trip operable channels requirements, and also Technical Specification 3.9.2 (Refueling Operation - Instrumentation) for SRH requirements.
In both cases the change indicates that the SRNs are not required (i.e., the minimum count rate for operability is not required) when 8 or fewer fuel assemblies (which would be adjacent to SRN) are in the core.
The bases for 3.9.2 is augmented to indicate the loading scheme.
The essence of the loading
- scheme, to provide a subcritical configuration while providing for a suitable count rate for the SRM and the subsequent well monitored loading for the remainder of the core, is the same as that proposed and approved for Browns Ferry.
The loading pattern to be used following SRN operability, which is directly interconnected to the SRfl, is somewhat different than the Browns Ferry central spiral loading pattern.
Our review has indicated that PPSL's proposal is more directly related to the SRYi count rate and is fully acceptable.
Conclusions PPEL has requested Technical Specification changes for Susquehanna Unit 2 which would remove during the loading (unloading) of the first (last) 8 fuel assemblies (adjacent to the SRN) the requirement that the SPM meet the minimum count rate requirement with fuel in the core.
Other loading require-ments will be unchanged.
The primary reason for wanting the change is to eliminate the need for FLCs ("dunking chambers")
during loading operations.
The primary basis for the safety of the requested change is that the core will be well below criticality during the loading of the 8 assemblies, and subsequent loading will be well monitored by the SRNs.
Our review has concluded that the process is acceptable and that the requested Technical Specification changes appropriately implement this process.
The NRC staff approves this change for Unit 2.
This same change was approved for Unit I on April 30, 1985.
Environmental Consideration This amendment involves a change in the installation or use of a facility component located within the restricted area 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 the individual or cumulative occupational radiation exposure.
The Commission has made a proposed no significant hazards consideration finding with respect to this amendment and has received no comments on such findings.
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 state-ment or environmental assessment need be prepared in connection with the issuance of this amendment.
Conclusion We have 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, and (2) such activities will be conducted in compliance with the Commission'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.
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