ML20237C909
| ML20237C909 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 12/16/1987 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20237C901 | List: |
| References | |
| IEB-79-26, NUDOCS 8712220252 | |
| Download: ML20237C909 (2) | |
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATING TO NPF-18 LICENSE CONDITION 2.C(6) 1 SURVEILLANCE FOR B0RON LOSS FROM BWR CONTROL BLADES l
COMMONWEALTH EDISON COMPANY LASALLE COUNTY STATION, UNIT 2 DOCKET NO. 50-374
1.0 INTRODUCTION
L By letter dated July 13, 1987, Commonwealth Edison (CE) submitted its response to IE Bulletin 79-26 Revision 1, " Boron Loss from BWR Control Blades," to satisfy NPF-18, License Condition 2.C(6) for LaSalle County Station, Unit 2.
The loss of boron carbide (B C) by leaching from cracked control blade 3
tubing is addressed in IE BuTletin 79-26, Revision 1, which requires operating BWRs to perform various actions including (1) determining baron depletion for individual control blades, (2) limiting the maximum extent of boron depletion in individual control blades under certain conditions, and (3) conducting shutdown-margin tests and modifying shutdown margin requirements to acconnodate the boron loss phenomenon.
2.0 EVALUATION The licensee's response to IE Bulletin 79-26 Revision 1, " Boron Loss from BWR Control Blades, is described as follows:
Item 1.
LaSalle is tracking control rod blade exposure history on a monthly basis in accordance with procedure, LTP-1600-29, " Control Blade End-of-Life Projection." Exposure records are maintained on 3-foot segments of each blade (4 segments per blade) on a con-tinuing basis.
Item 2.
Presently, LaSalle does not have any control blades which exceed 34 percent boron depletion (all blade segments are less than 10 percent depleted). A control blade will be discharged prior to exceeding 34 percent boron depletion for any 3-foot segment in accordance with LTP-1600-29.
Item 3.
Prior to the initial startup for LaSalle Unit 2, Cycle 2, a single rod subcriticality check (LTP-1600-30) was performed utilizing the analytically most reactive rod.
In addition, each control blade was individually fully withdrawn to perform CRD testing and criticality was not achieved.
8712220252 871216 PDR ADOCK 05000374 P
_m-n Alocalsubcritical-shutdownmargintest(LTS 1100-14) was performed on June.16,1987 (prior to initial criticality for Cycle 2) utilizing the strongest control rod, 54-43; 58-43 (symmetric rod to i
02-43, trie Fine Motion Control Rod Drive); and a rod diagonally adjacent to the strongest rod. With this three rod local shutdown margin demonstration, a shutdown margin of at least 1.372% WK/K was demonstrated, which is in excess of 1.232%
AK/K(.38%
6 K/K + R) required by Technical Specifications for Cycle 2.
A beginning o' cycle shutdown margin test (LTS-1100-1) was also determined from the initial criticality on June 16, 1987. The beginning of cycle shutdown j
margin was determined to be 2.81% AK/K for Unit 2.
A boron loss shutdown margin increment was not required for the Unit 2 Cycle 2 shutdown margin tests because all control blade segments are less than 34 percent depleted. A boron loss increment for future cycles will not be necessary since the General Electric B C original equipment control blades will be 3
discharged prior to exceeding 34 percent boron depletion.
The staff has reviewed the response stated in those three items above. Based on the review, the staff has found the response meets the requirements of IE Bulletin 79-26 and therefore, is acceptable.
3.0 CONCLUSION
Based on the above finding, the staff concludes that the licensee's response to IE Bulletin 79-26, Revision 1, " Boron Loss from BWR Control Blades," satisfies NPF-18, License Condition 2.C(6), and is acceptable.
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