ML20031D809
| ML20031D809 | |
| Person / Time | |
|---|---|
| Site: | 05000561 |
| Issue date: | 09/12/1977 |
| From: | Meyer R Office of Nuclear Reactor Regulation |
| To: | Vassallo D Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20031D800 | List: |
| References | |
| FOIA-81-236 NUDOCS 8110140238 | |
| Download: ML20031D809 (4) | |
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MEMORANDUM FOR:
D. B. Yassallo, Assistant Director for Light Water -
Reactors, DPM
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P. S. Check ' Chief, Core Performance Branch, DSS FROM:
, R. O. Heyn, Leader, Reactor Fuels Section, Core -
' - nee Branch, DSS Per
SUBJECT:
4PPLEMENT FOR BSAR-205 COiCERNING B C CO:frROL ' RODS 4
Plant Na:ne:
BSAR-205 Docket Nu:nber:
50-561 Milestone Number:
24-24 Licensing Stage: c PDA Responsible Branch,*
LWR-1 and Project Manager:
T. Cox Systems Safety Branch Involved:
Core Performa~nce Branch Description of Review:
SER Supple =ent Input.
Requested Completion Date:
August 25, 1977 Review Status:
Co=plete l
The Reactor Fuels Section of the Cote Perfor=ance Branch has prepared the attached supplement to the BSla-205 3ER. The supple =ent describes our review of the new B C control rod design. We conclude.that the design is g
acceptable for a PDA, but we will require licensees who use B C control 4
rods to submit plans for s'urwill nce to assure that courtol rod reactivity is not decreesed through some common mode failure mechanism..
,In addition, we are requesting B&W to submit a topical report on this
' new control rod design.
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Ralph O. Meyer, Section Leader Reactor Fuels Section Core Performance Branch Division of Systems Safety
Enclosure:
As stated DOCKET FILES NRR Reading File CPB Reading Pile
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DSS:CPB DSS:CPB DSS:CPB M.Tokar/cc RMeyer PCheck 9/ /77 9/ /77 9/ /77
.t 68110140238 810806 PDR FOIA
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.D. Ross P. Check W. Mcdonald W. Brooks D. Houston M. Tokar-e e
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B-SAR-205 B C CONTROL ROD ASSEMBLY 4
MATERIALS AND MECHANICAL - THERMAL DESIGN EJALUATION As noted in Section 4.2.3.2.1 of B-SAR-205, the control rod assemblies (CRAs) will be comprise'd of B C neutron absorber material clad with 4
cold-worked, type 304 austenitic stainless steel tubing. B-SAR-205 plants will be'the first BW reactors to use B C absorber material,in 4
their control rods; earlier plants have used Ag-In-Cd.
Although the probebility of cladding failure appears to be quite low, we have considered the behavior of the B C CRAs in the postulated case 4
of cladding perforation or failure.
Experimental evidence exists to show that irradiated B C has a higher solubility rate in water than 4
do2s the unirradiated material. Moreover, a manufacturing error recently
- led to failure of some Zircaloy-clad Al 0 4C burnable poison rods in 23 St. Lucie 1.
Approximately 10% of the initial boron loading was lost over a 2-month period as a result of partial dissolution of the slightly irradiated Al 0 4C in the PWR primary coolant. Although the resulting 23
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change in core nuclear characteristics was detected by in-core instrumentation in the St. Lucie plant, we are concerned that many of the B-SAR-205 B C CRAs will be in safety banks which are held out 4
of the core for emergency situations; they are not normally used ano, therefore, their reactivity worth is not normally observed. Since it seems unwise to permit safety rods containing soluble poison to remain in the reactor coolant for years without checking their reactivity worth or integrity, we will require licensees who use B C CRAs to 4
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w cub 2it plcna for routina curvaillance dreignsd to assure th:t tha reactivity invested in the control rods is not being lost through some common mode failure mechanism. An acceptable program might include several rod reactivity checks during the first core cycle and worth measurements of all the rod banks et refueling outages thereaf ter.
Another possibility involves the use of an isotopic " tag" material, which could signal the initiation and location of CRA cladding perforation.
In addition, we are requesting a topical report from B&W on design, testing, and material performance of B C CRAs.
This topical report 4
should be submitted at least one year prior to submittal of an FSAR on a B&W reactor incorporating B C absorber material in its CRAs.
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