ML19308C326
| ML19308C326 | |
| Person / Time | |
|---|---|
| Site: | Oconee, Arkansas Nuclear, Rancho Seco, Crane  |
| Issue date: | 04/28/1977 |
| From: | Stello V Office of Nuclear Reactor Regulation |
| To: | Heineman R Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19308C302 | List: |
| References | |
| TASK-TF, TASK-TMR NUDOCS 8001220728 | |
| Download: ML19308C326 (3) | |
Text
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NUCLEAR REGULATORY COMMISSION j
g wAsNiNoTON, D. C. 20655 j
e" APR 2 2 1977 4
1 MEM3RANDUM TO:
R. E. Heineman, Director, Division of Systems Safety FROM:
V. Stello, Jr., Director, Division of Operating Reactors
SUBJECT:
Operating Experience Memorandum No. 9 BABC0CK AND WILCOX REACTOR VESSEL SURVEILLANCE SPECIMEN HOLDER TUBES PROBLEM y(
Damage of varying degrees occurred to reactor-vessel surveillance-specimen holder tubes in each of the six operating facilities of Babcock
& Wilcox (B&W) nuclear design.
These facilities are Oconee 1, 2, and 3; Arkansas 1; Three Mile Island 1; and Rancho Seco. This holder tube con-I figuration consisted of three holder tubes, each housing two specimen T_
capsules, connected to the core barre' at the reactor vessel beltline t
by a journal bearing arrangement. The most severe damage occurred at y
Arkansas 1; portions of two of the three specimen holder tubes fell to A
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the bottom of the reactor vessel.
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PRESUMED CAUSE I
1 Failure of the reactor vessel surveillance specimen holder tubes was I
caused by flow induced vibrations which resulted in an impact phenomena L
between the spacer on the capsule withdrawal rods and the holder tubes.
SAFETY SIGNIFICANCE g
Z The release of holder tube debris presents a potential source if damage
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to the lower pcrtion of the fuel assemblies; blockage of coolant flow to a
the fuel assemblies; and the possibility that debris could enter a control
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rod guide tube and interfere with control rod motion.
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REPAiP; 3
E At each of the six facilities all surveillance capsules and most of the y
parts of the holder tube assemblies were removed from the reactor vessels, g
A limited term exemption was granted from the provisions of Appendix H, y
10 CFR 50, which permit operation of the reactors with the surveillance p
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2 C O R. E. Heineman u.
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l specimens removed for the balance of the present cycles; and each technical specification was amended, including a requirement that the w
specimens (except those subjected to destructive testing) be re-installed p
m prior to the next cycle, g
DDR ACTION n
The new design has been installed i
B&W has redesigned the holder tube.
y in Davis-Besse 1, Crystal River 3, and Three Mile Island 2 which are l
These installations undergoing, or approaching, initial operat. ion.
were made prior to neutron activation of the three reactors and no b,
Each of the six older D
particular difficulties were encountered.
f acilities, and the three newer units have the basic B&W 177 fuel assembly design.
s The redesigned holder tube assentlies are rigidly secured to the core 5
r.
The new configuricion consist of six holder tubes, each Design verification was provided during j
barrel.
containing two capsules.
recent hot-functional testing at Cavis-Besse 1 using accelerometer and strain gage instrumentation.
Acquired data confinns that the redesigned holder tube is capable of withstanding the dynamic environment to which 7
it is subjected.
I kj Installation of the redesigned holders in the six irradiated facilities
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would cause significant radiation to workmen.
An estimate has been made by B&'4 that the personnel exposure would be about 100 man-rem per
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An integrated surveillance program has been proposed by B&W r
reac tor.
and the affected licensees which would not require reinstalling the I
surveillance specimens in the six older facilities.
U We are in the process of evaluating the integrated reactor-vessel material b
surveillance program to insure continued compliance with Appendix H,10 CFR part 50 and ASTM E 185-73.
L The Mechanical Engineering Branch and the Materials Engineering Branch e
b of DSS have been kept informed on these actions, and we will continue p
to coordinate our efforts with them.
i RECOMMENDATIONS L
i The DOR staff qas evaluated the adequacy of the redesigned reactor h
This assessment included vessel surveillance specimen holder tube.
I detailed study of the design concepts; on-site observations at Davis-Besse 1; and discussions with B&W concerning both the design bases and
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test results obtained at Davis-Besse 1.
We recommend that this design i
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AN : b G7, R. E. Heineman p e
be approved for installation in those B&W plants that have not yet s
received an operating license.
In our judgment this design is sufficient to provide assu*ance of adequate safety margins against structural failure.
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B&W will submit within the next few weeks a report covering the details h
of the redesign and the test results obtained at Davis-Besse 1.
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PRINCIPAL DDR PERSONNEL E
f Reviewers:
V. Noonan W. Hazelton t
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s' Vicfor Stelle, Jr., Director l
Division of Operating Reactors b
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E. Case S
S. Hanauer E
R. Boyd i:
H. Denton F. Schroeder
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DSS ads D0R ads K
V. Noonan 7
L. Nichols
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