ML19210D584
| ML19210D584 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 11/21/1979 |
| From: | Howard J BOSTON EDISON CO. |
| To: | |
| References | |
| NUDOCS 7911270345 | |
| Download: ML19210D584 (5) | |
Text
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e BOSTON EDISON COMPANY 8o0 BoYLSToN STREET GoSToN, MASSACHUSETTS 02199 J. EoWARo HoWARo v.cs pensiosa, muc6ama November 21, 1979 BEco. Ltr. #79-233 Proposed Change No. 79-6 Mr. Thomas A. Ippolito, Chief Operating Reactors Branch #3 Division of Operating Reactors Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D. C.
20555 License No. DPR-35 Docket No. 50-293 Proposed Technical Specification Change Concerning Required Counts on SRM during Fuel Movements
Dear Sir:
Introduction Pursuant to Section 50.90 of the Commission's Rules and Regulations, Boston Edison Company hereby proposes the following modification to Appendix A of Operating License No. DPR-35.
Proposed Change Change Specificiation 3.10.B.2 to read "The SRM shall have a minimum of 1.
3 cps except as specified in 3 and 4 below.
2.
Add paragraphs 3 and 4 as follows:
"3.
Prior to spiral unloading, the SRM's shall have an initial count rate oft 3 cps. Euring spiral unloading, the count rate on the SRM's may drop below 3 cps.
During spiral reload, SRM operability will be verified by using a 4.
portable external source every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> until the required amount As an alternative to the of. fuel is loaded to maintain 3 cps.
above, up to two fuel assemblies will be loaded in different cells containing control blades around each SRM to obtain the required Until these assemblies have been loaded, the cps require-3 cps.
ment is not necessary."
1397 128 Reason for Change During the next fuel outage, the antimony - berylium neutron sources will be This removal is a result of experience at other BWR's removed from the core.
7 D112 70 3b
BOSTON EDISDN COMPANY Mr. Thomas A. Ippolito, Chief November 21, 1979 Page 2 of startup source holder failures. Removal of these sources should have no effect on normal outages (s 120 days) when fuel with greater than 5000 MUD /T average exposure is left in the core. However, for cases in which the fuel is fully unloaded there will not be a source of neutrons to satisfy the Technical Specification requirements of ? 3 cps on the startup range monitors during initial fuel reloading, nor during the final steps of future full core unloadings. The proposed Technical Specification changes will allow necessary full core discharge and reloading provided the fuel is moved in a spiral pattern.
Clariffcation A spiral unloading pattern is one by which the fuel in the outermost cells (four fuel bundles surrounding a control blade) is removed first. Unloading continues by removing the remaining outermost fuel cell by cell.
The center cells will be the las t removed.
Spiral loading is the reverse of unloading. Spiral unloading and reloading will preclude the creation of flux traps (moderator filled cavities surrounded on all sides by fuel).
During spiral unloading, the SRH's shall have an initial count rate of z 3 cps with all rods fully inserted. The count rate will diminish during fuel removal.
Under the special condition of complete spiral core unloading, it is expected that the count rate of the SRM's will drop below 3 cps before all of the fuel is unloaded.
Since there will be no reactivity additions, a lower number of counts will not present a hazard. When all of the fuel has been removed to the spent f uel storage pool, the SRM's will no longer be required.
Requiring the SRM's to be operable prior to fuel removal assures that the SRM's are operable and can be relied on even when the count rate may go below 3 cps.
During spiral reload, SRM operability will be verified by using a portable exter-ne' source every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> until the required amount of fuel is loaded to maintain 3 cps. As an alternative to the above, up to two fuel assemblies will be loaded in different cells containing control blades around each SRM to obtain the required 3 cps. Until these two assemblies have been loaded, the 3 cps requirement is not necessary.
Safety Considerations The proposed Technical Specification will allow spiral unloading of the full core and subsequent spiral reloading with less than 3 cps on the SRM when only a few aseemblies are in the core.
The lack of countrate is considered acceptable since:
1.
Adequate shutdown margin will exist as discussed below.
2.
The SRM'b will be verified to be operable 3.
IRM detectors will provide scram protection in the unlikely event of criticality in these small arrays.
Note that the SRM's presently are not required to perform any automatic safety function nor are they relied upon in safety analyses to mitigate the consequences of any accidents during core alterations.
397 129
BOSTOA EDISDN COMPANY Mr. 'Ihomas A. Ippolito, Chief November 21, 1979 Page 3 Because of the nature of spiral loading / unloading, the intermediate fuel arrays will be subcritical at all times. Neither imbedded cavities nor major per-ipheral concavities are possible since the spiral sequence does not allow the removal of adjacent fuel cells.
Since with this sequence a single unloaded cell results in local flux which is less than or equal to the flux prior to cell unload, the multiplication factor of intermediate fuel arrays is less than or equal to that of a fully loaded core.
Since peripheral concavities are not allowed approximate core symmetry is maintained with a like number of cells removed from each core quadrant at any point in the sequence. Thus, flux peaking in any one quadrant due to an inbalance of unloaded cells is precluded. Therefore, the multiplica-tion factor for the entire core is less than or equal to that of a fully loaded core, the shutdown margin of which is assured by other specifications.
This change has been reviewed Nuclear Safety Review and Audit Committee and reviewed and approved by the Operations Review Committee.
Schedule of change Boston Edison Company intends to commence a refueling outage at Pilgrim Nuclear Power Station Unit #1 in January 1980. Use of this Technical Specification Change at the outset of the outage would be desirable, thus this change will be put into effect upon receipt of approval of the Commission.
Fee Consideration In accordance with Section 170.12 of the Commission's Regulations, Boston Edison proposes this license change as Class III.
Accordingly a check for Four Thousand
($4,000) is enclosed.
Should you have. any questions on this subject, please do not hesitate to contact us.
Very truly yours, Attachments:
D W
Exhibit A v
3 signed originals and 37 copies Commonwealth of Massachusetts)
County of Suffolk
)
Then personally appeared before me J. Edward Howard, who, being duly sworn, did state that he is Vice President - Nuclear of Boston Edison Company, the applicant herein, and that he is duly authorized to execute and file the submittal contained herein in the name and on behalf of Boston Edison Company and that the statements in said submittal are true to the best of his kn9wledge and belief.
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1397 130 7/0 f (, /9f'M
/WMNu My Commission expires:
Notdry Public '
Exhibit A LIMITING CONDITIONS FOR OPERATION SURVEILLANCE REQUIREMENTS 2.
The SRM shall have a minimum of 3 cps with all rods fully in-serted in the core.
3.
Prior to spiral unloading, the SRM's shall have a. initial count rate of23 c.;s.
During spiral unloading, the count rate on the SRM's may drop below 3 cps.
4.
During spiral reload, SRM operability will be verified by using a portable external source every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> until the required amount of fuel is loaded to maintain 3 cps. As an alternative to the above, up to two fuel assemblies will be loaded in different cells con-taining control blades around each SRM to obtain the required 3 cps. Until these assemblies have loaded, the cps requirement is not necessary.
/
t i397 131 203
3.10 BASES 8.
Core Monitoring The SRM's are provided to monitor the core during periods of station shutdown and to guide the operator during refueling operations and station startup.
Requiring two operable SRM's in or adjacent to any core quadrant where fuel or control rods are being moved assures adequate monitoring of that quadrant during such alterations. The requirement of 3 counts per second provides assurance that neutron flux is being monitored and insures that startup is conducted only if the source range flux level is above the minimum assumed in the control rod drop accident.
The limiting conditions for operation of the SRM subsystem of the Neutron Monitoring System are derived from the Station Nuclear Safety Operational Analysis (Appendix G) and a functional analysis of the neutron monitoring The specification is based on the Operational Nuclear Safety Re-system.
quirements in subsection 7.5.10 of the Safety Analysis Report.
A spiral unloading pattern is one by which the fuel in the outermost cells (four fuel bundles surrounding a control blade) is removed first. Unloading continues by removing the remaining outermost fuel cell by cell. The center cell will be the last removed.
Spiral loading is the reverse of unloading. Spiral unloading and reloading will preclude the creatio a of flux traps (moderator filled cavities surrounded on all sides by fuel).
During spiral unloading, the SRM's shall have an initial count rate of 2 3 cps with all rods fully inserted. The count rate will diminish during fuel removal.
Under the special condition of complete spiral core unloading, it is expected that the count rate of the SRM's will drop below 3 cps before all of the fuel is unloaded.
Sidce there will be no reactivity additions, a lower number of counts will not When all of the fuel has been removed to the spent fuel storage present a hazard.
pool, the SRM's will no longer be required. Requiring the SRM's to be operational prior to fuc1 removal assures that the SRM's are operable and can be relied on even when the count rate may go below 3 cps.
During spiral reload, SRM operability will be verified by using a portable exter-nalisource every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> until the required amount of fuel is loaded to maintain 3 cp's.
As an alternative to the above, up to two fuel assemblies will be loaded in diff'erent cells cc itaining control blades around each SRM to obtain the required 3 cps.
Until these assemblies have been loaded, the 3 eps requirement is not necessary.
C.
Spent Fuel Pool Water Level _
To assure that there is adequate water to shield and cool the irradiated fuel assemblies stored in the pool, a minimum pool water level is established.
The minimum water level of 33 feet is established because it would be a significant change from the normal level (-l foot) and is well above the level to assure adequate cooling.
4.10 BASE 1 A.
defueling Interlocks Complete functional testing of all refueling interlocks before any refueling outage will provide positive indication that the interlocks operate in the situations for which they were designed. By loading each hoist with a weight equal to the fuel assembly, positioning the refueling platform, and with-drawing control rods, the interlocks can be subjected to valid operational Where redundancy is provided in the logic circuitry, tests can be tests.
performed to assure that each redundant logic element can independently perform its functions.
l397 132 B.
Core Monitoring Requiring the SRM's to be functionally tested prior to any core alteration 205 assures that the SRM's will be operable at the start of that alteration.
The daily response check of the SRM's ensures their continued operability.