ML19291C331
| ML19291C331 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 12/17/1979 |
| From: | Daltroff S PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| IEB-79-26, NUDOCS 8001240214 | |
| Download: ML19291C331 (5) | |
Text
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71 PHILADELPHIA ELECTRIC COMPANY 2301 M ARKET STREET P.O. BOX 8699 PHILADELPHI A. PA.19101 SHIELDS L. DALTROFF VICE PRESIDENT ELECTRIC PRODUCTION December 17, 1979 Docket Nos.: 50-277 50-278 Re: IE Bulletin 79-26 Mr. Boyce H.
Grier, Director Office of Inspection & Enforcement Region I United States Nuclear Regulatory Commission 631 Park Avenue King of Prussia, PA 19406
Dear Mr. Grier:
This letter is in response to IE Bulletin 79-26, forwarded to us on N ove mb e r 20, 1979, concerning boron loss from BWR control blades.
Responses to each concern are given sequentially below.
Action to be Taken bv Licensees 1.
The op erating his t ory of the reactor is to be reviewed t o establish a record of the current B10 depletion averaged over the upper one-f ourth of the blade for every control blade; the record is to be maintained on a continuing basis.
This action is required on all reactors whether shutdown for refueling or operating.
Response
During the last several years, Philadelphia Electric Company has carried out a p rogram f or review of control blade operating history.
This program includes determining and maintaining a record of the cu rrent B10 depletion averaged over the upper one-fourth of each control blade.
It is planned to maintain this program on a continuing basis or as long as B4C type control blades are utilized in the reactor system.
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'M r. Boyce H.
Grier Page 2 2.
Identify any control blades predicted to have greater than 34 % B10 depletion averaged over the upper one-fourth of the blade by the next refueling outage.
a.
Describe your plans for replacement of identified control blades.
b.
Describe measures which you plan to take justifying continued operations until the next refueling specifically addressing (1) any blade with greater than 42% depletion averaged over the upper one-fourth of the blade; and (2) the condition where you find greater than 26% of the control blades calculated to have greater than 34% depletion averaged over the upper one-fourth of the blade.
Response
Based on our latest evaluations, which include operating hist ory through October 31, 1979, no control blades at Peach Bottom Units 2 and 3 exceed 34% B10 depletion.
In addition, no blades are predicted to exceed 34 % B10 depletion during the remainder of the current op erating cycles up to the next refuelings.
Therefore, no control blade replacements are planned during the current operating cycles.
Should any control blade exceed 42% depletion or should greater than 26% of the control blades exceed 34 % dep letion, a safety review will be conducted to assure such conditions are bounded by the p lan t 's Technical Specifications and do not pose an unreviewed safety concern.
As stated above, no blades are exp ected t o exceed 34 % depletion prior to the next refuelings; theref ore, the above conditions are extremely unlikely.
Further, through the continuing p rogram f or monitoring blade performance, it is Philadelphia Electric's intention to avoid the above conditions from occurring through control blade change-out or control blade operating strategy.
3.
At the next cold shutdown or refueling outage, conduct shutdown margin tests to verify that:
a.
full withdrawal of any control blade from the cold xenon-free core vill not result in criticality; and b.
compliance with the shutdown margin requirement in a manner that accommodates the boron loss phenomenon (i.e.,
by including a plant specific increment in the shutdown margin that takes the potential loss of boron from control blades identified f rom evaluation of Item, 1 into consideration).
Mr. Boyce H.
Grier Page 3
Response
If any control blade exceeds or is predicted to exceed 34 % B10 depletion averaged over the upper one-f ourth of the blade (10%
reduction in rod worth taking boron loss into consideration), the shutdown margin will be demonstrated to be at least the sum of the shutdown margin required by Technical Specifications plus an increment sufficient to account for the p otential f or boron loss.
A calculation will be perf ormed and provided at the time of such an occurrence to establish an additional shutdown margin increment which accounts f or p otential boron loss.
Each control blade will be fully withdrawn ro demonstrate suberiticality at the next refueling outage.
This testing was successfully completed f or Peach Bottom Unit 3 during the unit's startup tes ting f ollowing its third refueling which was completed in early November, 1979.
Attachment 1, which provides a written report on this testing, is provided in' fulfillment of the Bulletin No. 79-26 item 3.a request.
Since no control blades are expected to exceed 34 % B10 depletion during the remainder of Peach Bottom Unit 2's current operating cycle, this testing will be performed on Unit 2 at its next refueling outage s cheduled f or the Spring of 1980.
Since no blades exceeded 34% B10 depletion at Peach Bottom Unit 3's recent refueling outage (maximum was 19. 4 %) nor was any blade predicted to exceed 34 % during its current op erating cy cle, no blades were predicted to exceed their design life taking boron loss into account.
Therefore, it was not necessary to include any additional shutdown margin (adder) to account f or p otential boron loss during the shutdown margin demonstration conducted during Unit 3's startup testing.
Should future predictions during the operating cycle sh ow that any blade will exceed 34%
B10 depletion, a report will be provided to demonstrate that the shutdown margin demonstrated during the startup testing is sufficient to meet Technical Specification requirements plus any additional shutdown margin t o accommodate the p otential f or boron loss.
Since Unit 3 demonstrated a shutdown margin of
- 1. 6 % A K/ K during startup testing and the Technical Specification requirement is 0.38 % A K/K, a large margin is available to cover such an occurrence.
Bulletin No. 79-26 item 3.b request will be provided f or Peach Bottom Unit 2 on the schedule requested.
As indicated earlier, however, it is Philadelphia Electric's intention t o avoid operation with blades of excessive B10 depletion.
Therefore, it is unlikely that a written report on item 3.b will be necessary.
4.
Perf orm a destructive examination of the most highly exp os e d control blade at the end of the next cycle and p rovide results of *he examination within one calendar year after removal of the blade.
The results to be rep ort e d 's h ould '
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include:
Mr. Boyce H.
Grier Page 4 a.
Tube number or identification. '
b.
The evaluation of each crack in the tubing.
c.
The calculated B10 depletion versus elevation for each tube.
d.
The measured B10 loss versus elevation f or cach tube.
e.
The maximum local depletion for tubes having no cracks.
f.
The maximum local depletion for tubes having no loss of boron.
Alternatively, the results of a de s t ru ct ive examination of a blade of limilar fabrication and operat! onal hir t ory may be provided withic cne year of the date of issuance of this bulletin.
If the highest local B10 depletion is less than 50%, this examination can be deferred until the next refueling.
Response
Philadelphia Electric is reviewing several alternatives to determine a course of action to best respond t o this request.
A response to this item will be provided in accordance with the schedule requested.
If you require any additional inf ormation or have any questions, please contact us.
Very truly yours,
f'
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e Attachment cc:
U.
S. Nuclear Regulatory Commission Office of Inspection & Enforcement Divisions of Reactor Operations Inspection Washington, DC 20555 1795 068
Mr. B oyce H.
Grier Page 5 Attachment for Bulletin No. 79-26 Response Control Blade Suberiticality Testing Peach Bottom Atomic Power Station Unit 3 The following is provided f or Peach Bottom Atomic Power Station Unit 3 in response to Bulletin No. 79-26, item 3.
Peach Bottom Unit 3 completed its third refueling in early November, 1979 A startup test program was conducted following this refueling which included both control blade subcriticality testing and shutdown margin testing.
The control blade suberiticality testing was conducted in accordance with an approved procedure (Surveillance Test 10.8).
During this testing, each control blade was fully withdrawn and the reactor was demonstrated to remain suberitical.
The shutdown margin testing was conducted in accordance with surveillance Test 3 8.3.
Shutdown margin was demonstrated to be
- 1. 6 % o K/ K, comp are d to the Technical Specification requirement of 0.38 % AK/ K.
Since no control blade exceeds 34% B10 depletion (maximum is 19. 4 %) nor are any blades expected to exceed 34% during cycle 4,
it was not necessary to include an additional shutdown margin increment for potential boron loss.
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