United States Nuclear Regulatory Commission - Protecting People and the Environment

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. 
Page Last Reviewed/Updated Tuesday, July 23, 2013