Bulletin 80-03: Loss of Charcoal from Standard Type II, 2 Inch, Tray Adsorber Cells
SSINS No.: 6820
Accessions No.:
7912190669
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555
February 6, 1980
IE Bulletin No. 80-03
LOSS OF CHARCOAL FROM STANDARD TYPE II, 2 INCH, TRAY ADSORBER CELLS
Description of Circumstances:
During preliminary leak tests of charcoal adsorber cells in certain
ventilation systems at Sequoyah Nuclear Plant, it was determined that on
certain adsorber cells the spacing between rivets securing the perforated
screen to the casing was too great to ensure adequate contact between the
casing and the screen, thus allowing charcoal to escape.
The problem was discovered when a visual inspection detected loose charcoal
on the floor of the filter housings and on the outside horizontal surfaces
of the adsorber cells. Loss of charcoal was also indicated by observation of
light penetrating through the cells. Additional inspection revealed that the
rivets securing the perforated screens to the cell casing were approximately
six inches apart and the screen appeared to be sagging away from the casing
between rivets.
The particular adsorber cells being tested at Sequoyah Nuclear Plant were
Flanders Type II pre-1974 fabrication.
There is a possibility that design of adsorber cells with wide spacing
between screen rivets may pass initial freon leak tests but degrade
significantly during operation thus reducing the margin of safety during
postulated accidents.
The responses from this Bulletin will be used by the NRC to evaluate need
for more frequent inspection/testing.
For all power reactor facilities with an Operating License:
1. Determine if charcoal adsorber cells in use, or proposed for use, have
the potential for a loss of charcoal incidental to handling, storage or
use (as appropriate). Particular attention should be directed to
examination of a) rivet spacing resulting in separation of screen and
cell housing and b) adsorber cell or filter housing deformation causing
loss of charcoal and/or channeling. Either of these items could result
in a degraded filtration system incapable of performing its intended
function. The preferred method of this determination is a visual
inspection of the filter housing and adsorber cells as described in
Section 5 of ANSI N510-1975. If this method is not feasible, state in
the report required by Paragraph 4 how the determination was made.
2. For ESF filtration systems, any identified defective cells shall be
replaced and the operability of the system (after cell replacement)
.
IE Bulletin No. 80-03 February 6, 1980
Page 2 of 2
demonstrated by leak testing within 7 days. Preferred method of leak
testing is as described in Regulatory Guide 1.52 and Section 12 of ANSI
N510-1975.
3. For normal ventilation exhaust filtration systems which employ charcoal
adsorber cells and for which radioactive removal efficiency has been
assumed in determining compliance with the "as low as reasonably
achievable" design criteria of 10 CFR 50, Appendix I, any identified
defective cells shall be replaced as soon as possible but at least
within 30 days. After replacement, the system should be demonstrated
operable by leak testing within an additional 30 days. Preferred method
of testing is as described in Regulatory Guide 1.140 and Section 12 of
ANSI N510-1975.
4. Report in writing within 45 days of the date of this Bulletin the
results of the determination required by Paragraph 1. The report shall
include the type of cells employed (manufacturer and cell design),
system containing the cells, observed cell condition
(degradation/sagging) and a discussion of visual inspection procedure
and results.
For all Power Reactor Facilities with a Construction Permit:
1. Visual inspection shall be conducted only if the charcoal adsorber
cells have been purchased and shipment received. A representative
number (approximately 5) of each type of cell design/manufacturer shall
be visually inspected for such deficiencies as rivet spacing and
screen/casing separation which could lead to loss of charcoal
incidental to handling, storage, or use.
2. Report in writing within 45 days of the date of this Bulletin the
results of the inspection required by Paragraph 1. The report shall
include the type of cells (manufacturer and cell design), observed cell
condition (degradation/sagging) and a discussion of the inspection
procedure and results.
Reports shall be sent to the Director of the appropriate NRC Regional Office
listed in Appendix D of 10 CFR 20 with a copy of the Director, Division of
Fuel Facility and Materials Safety Inspection, Office of Inspection and
Enforcement, USNRC, Washington, D.C. 20555.
Approved by GAO, B180225(ROO72); clearance expires, 7/31/80. Approval was
given under a blanket clearance specifically for identified generic
problems.
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