United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 97-58: Mechanical Integrity of In-Situ Leach Injection Wells and Piping

                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
              OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS
                        WASHINGTON, D.C. 20555-0001

                                July 31, 1997


NRC INFORMATION NOTICE 97-58:  MECHANICAL INTEGRITY OF IN-SITU LEACH           
                               INJECTION WELLS AND PIPING


Addressees

Holders of and Applicants for Licenses for In-Situ Leach Facilities.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
notice to alert licensees to leaks related to faulty coupling and
configuration of piping at in-situ leach facilities.  Recipients should review
the information notice for applicability to their  facilities and consider
actions, as appropriate, to prevent similar problems.  However,
recommendations contained in this information notice are not NRC requirements;
therefore, no specific action or written response is required.

Description of Circumstances

In one case, an injection well (IW) leak, detected during routine 5-year
mechanical integrity testing (MIT), caused an excursion above the ore zone. 
In a separate incident, a failure occurred in an injection trunk line,
resulting in a spill of barren lixiviant.

1.  IW Leak:

A leak in an IW was detected during routine 5-year MIT work.  Further testing
identified  a faulty coupling 12 meters (40 feet) below the ground as the
source of the leak.  Initial operation of the leaking IW occurred from March
1992 to September 1994.  The well was then dormant from October 1994 to
October 1995.  A lixiviant re-circulation, using extraction water that had not
passed through the ion exchange facility, was initiated in November 1995 and
lasted until January 1996.  The well was then dormant until the MIT of March
1996.  

After the MIT results, a monitoring well (air drilled) was installed to the
proper depth interval to monitor around the IW for groundwater contamination
in the shallow fresh water aquifer.  An excursion was detected in a monitoring
well, 3 meters (10 feet) from the IW.  The sample from this well had a
conductivity of 5540 uMho/cm and 27.6 ppm uranium oxide (U3O8 ).  Normal
aquifer conductivity is 300 Umho/cm.  Pursuant to conditions in the license
agreement, the licensee informed NRC of the excursion within 24 hours of
detection.  Additional shallow monitoring wells were installed around the IW
to begin delineation of the 

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excursion.  Monitoring wells 30 to 42 meters (100 to  138 feet) from the IW
were at normal background levels for conductivity and uranium concentrations.

The licensee is taking corrective action by pumping the contaminated shallow
monitoring wells to recover the excursion.  The effectiveness of the fluid
recovery operation will  be monitored by weekly sampling of the contaminated
shallow monitoring wells and the shallow monitoring wells outside the
excursion limits.  These weekly groundwater samples will be analyzed for
sodium, chloride, sulfate, alkalinity, and conductivity.  The licensee 
has concluded that a pressure buildup, caused by the downhole oxygen (O2)
injection sys- tem, led to the loss of integrity at the casing coupling in the
IW, and  that minor excursions occurring in other IWs have similar causes. 
The licensee plans  to remove the O2 stingers from injection wells.

2.  Trunk Line Failure:

A leak was detected in a primary injection trunk line which supplies barren
lixiviant to  the well fields.  The trunk line system consists of two 30-cm
(12-in) diameter high density polyethylene buried lines (one injection line,
one recovery line) that carry lixiviant to and  from the plant to the various
well fields.  The failure consisted of a separation at a fusion weld, where a
30-cm to 20-cm (12-in to 8-in) short reducer was welded onto the 30-cm (12-in)
line.

The licensee believes the failure of the fusion weld was caused by the
configuration of the line reducer and 90-degree tee at this point in the
system.  The full injection flow placed a large stress on the short reducer,
before making the 90-degree turn toward the well fields.  The trunk line has
been repaired, with the 90-degree tee replaced with a 30-cm (12-in) steel
elbow with threaded ends and a gentler bend.  An investigation of the trunk
line systems found this configuration, where the failure occurred, unique.

Discussion

The licensees are addressing corrective action and cleanup for these incidents
pursuant  to clean-up and restoration license conditions and/or site
procedures.  No new NRC requirements have been established for the involved
licensees or other licensees as a  result of these incidents.   Excursions
from losses of mechanical integrity in wells are generally preventable since
they are often manifested by structural weaknesses induced by improper well
construction.  Licensees with similar IW arrangements should be aware that
more frequent integrity testing may be necessary to prevent this type of
excursion  in the future.  Likewise, licensees should avoid piping
configurations similar to the 90-degree  bend in the trunk line.  The staff
plans to thoroughly review data associated with similar piping/injection
arrangements at other licensee facilities during future inspections.
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This information notice requires no specific action or written response.  If
you have any questions about the information in this notice, please contact
the technical contact listed below.


                                                    signed by

                                        John T. Greeves, Director
                                        Division of Waste Management
                                        Office of Nuclear Material Safety
                                          and Safeguards

Technical contact:  J. Robert Tinsley, NMSS
                    (301) 415-6251
                    E-mail:  jrt1@nrc.gov
Page Last Reviewed/Updated Tuesday, December 03, 2013