**NRC INSPECTION MANUAL** NMSS/IMNS

TEMPORARY INSTRUCTION 2800/037, Revision 1

SAFETY PROCEDURES FOR PANORAMIC IRRADIATORS

CORNERSTONE: RADIATION SAFETY

APPLICABILITY: This TI applies to the inspectors responsible for
implementing the Focus Elements of Inspection Procedure 87122,
"Irradiator Programs."

2800/037-01 OBJECTIVES

01.01 To determine if activities authorized pursuant to 10 CFR Part 36,
"Licenses and Radiation Safety Requirements for Irradiators" are
conducted safely.

01.02 To determine the extent to which irradiator operators may need to
defeat, or have defeated, interlocks for any reason, including to effect
repairs of the irradiator.

01.03 To determine if licensees have procedures or practices for the
defeat of interlocks and enter the irradiator. If so, to determine if
such procedures are adequate to protect workers from radiation exposure.

01.04 To determine irradiator operators' knowledge and understanding of
functions and limitations of equipment, particularly the safety
interlocks and the methods to verify radiation levels inside the
irradiator.

01.05 To determine irradiator operators' knowledge and understanding of
events that would require them to implement emergency response
procedures, and to determine if there is a clear link between normal
operating procedures and emergency/abnormal operating procedures.

2800/037-02 BACKGROUND

This Temporary Instruction provides additional direction to inspectors
in implementing the Focus Elements of Inspection Procedures 87122,
"Irradiator Programs", during the

next cycle of inspections of panoramic irradiators.

As a result of an event at a panoramic irradiator on April 21, 2004, the
NRC learned that, under certain conditions, an irradiator licensee has
defeated safety interlocks in order to enter the irradiator to effect
repairs. In the case of the irradiator involved in the April 21, 2004,
event, the programmable logic controller \[PLC\] verifies that the
source rack is in its safe storage position by confirming that all the
source-rack-down indicator switches are properly activated. This should
occur when the source rack reaches its fully descended position and
comes in contact with the source-rack-down indicator switches. If the
PLC cannot confirm that the source-rack-down indicator switches are all
properly activated, it is assumed the source rack is NOT in its safe
storage positions and the PLC prevents entry into the cell and activates
alarms and indicators to identify that a fault has occurred. If the
source rack is actually in its safe storage position, then there is a
problem with the source-rack-down indicator switches (or the signals
from them). In this irradiator facility, it then becomes necessary to
defeat the interlocks in order to gain entry into the irradiator to
repair the switches. In the April 2004 event, the licensee did not
consider this type of problem to require implementation of emergency
procedures. The licensee in this case used an informal, unwritten
practice that did not include redundant verification of the radiation
levels inside the irradiator or verification of the position of source
racks prior to entry; instead, it relied only on use of a portable
survey instrument to identify unusual radiation levels during entry
procedures.

On April 21, 2004, two such problems occurred in which the irradiator
PLC system could not verify that the source racks were in a safe storage
position, and therefore caused the interlocks to prevent entry. During
the first occurrence on that day, the source racks were, in fact, in the
safe storage position, and an irradiator operator defeated the
interlocks, entered the irradiator, and repaired switches. In the second
occurrence, however, one of the source racks was stuck in an unshielded
position but employees did not know this. After defeating the
interlocks, an irradiator operator and an assistant walked a short way
into the irradiator prior to noticing elevated radiation levels on a
portable survey instrument. They received doses of 4.4 rem and 2.8 rem,
respectively, by the time they turned around and exited the irradiator.
NRC inspectors estimated that, if the two workers had continued on their
intended path through the irradiation room, each worker would have
received a dose of about 450 rads, which is potentially lethal.

The NRC was unaware of any circumstances at an irradiator which required
defeat of interlocks in order to effect repair of the operation of the
irradiator. Regulations in 10 CFR 36.23 require access controls to
prevent inadvertent entry of personnel if sources are not in a shielded
position, but does not address deliberate defeat of interlocks in order
to effect repair of systems inside the irradiator causing the interlocks
to prevent entry. Regulations in 10 CFR 36.67 require the use of a
survey meter when entering the irradiator room after an irradiation to
determine that sources are returned to a shielded position, but does not
address use of survey meters after raising and lowering the source rack
for testing purposes.

Regulations in 10 CFR 36.53 require, in part, that licensees perform a
drill of one of the emergency procedures each year, but does not specify
that drills should vary the emergency procedure from year to year. In
this case, licensee personnel practiced the same emergency drill each
year, and never practiced their response to a stuck source event.

The source rack was prevented from returning to its safe storage
position because a ladder, left in the irradiator room following repair
activities, lodged under the source rack when it descended again after
being raised to test repairs of the switches. There are no NRC
regulations or guidance which direct licensees to ensure that no
obstructions remain in the source rack path prior to raising the source
rack.

2800/037-03 INSPECTION REQUIREMENTS

03.01 Inspectors should perform a routine inspection in accordance with
Manual Chapter 2800 and Inspection Procedure 87122 to determine if
activities authorized pursuant to 10 CFR Part 36, "Licenses and
Radiation Safety Requirements for Irradiators" are conducted safely.
This inspection should include interviews with as many operators,
maintenance staff, and others involved in the operation of the
irradiator as possible, as well as licensee management,

03.02 inspectors should determine the extent to which irradiator
operators may need to defeat interlocks, or have defeated interlocks,
for any reason such as to effect repairs of the irradiator. Inspectors
should determine if there is potential for such an event at the
irradiator facility. If such event(s) have occurred, inspectors should
review when the event(s) occurred, how often, and the licensee's actions
during such event(s).

03.03 Inspectors should determine if licensees have procedures or
practices for the defeat of interlocks and entry of the irradiator. If
so, inspectors should review the circumstances under which the licensee
has, or would, defeat interlocks, and the inspector should review the
procedures or practices to determine if they are adequate to protect
workers from radiation exposure.

03.04 Inspectors should determine irradiator operators' knowledge and
understanding of the functions and limitations of equipment,
particularly the safety interlocks and the methods to verify radiation
levels inside the irradiator. Inspectors should determine if the
operators have a method of determining the position of the source rack
and the radiation levels inside the irradiator other than use of a
portable survey meter during entry.

03.05 Inspectors should interview irradiator operators to determine
their level of knowledge and understanding of events that would require
them to implement emergency response procedures, and to determine if
there is a clear link between normal operating procedures and
emergency/abnormal operating procedures.

2800/037-04 GUIDANCE

Inspection Procedure 87122, "Irradiator Programs"

NUREG-1556, Volume 6, "Consolidated Guidance About Materials Licensees,
Program Specific Guidance About 10 CFR Part 36 Irradiator Licenses"

2800/037-05 REPORTING REQUIREMENTS

Inspectors should provide a separate summary report briefly describing
the results of the inspections of Items 0.03.01 through 03.05. The
summary report should include the name, license number, docket number
and address of the licensee; the date of the inspection; the inspector's
name, and the results of the items listed in this TI. Summary reports
should be submitted within 30 days of the completion of the inspection.
The summary reports should be sent to Michael K. Williamson, Rulemaking
and Guidance Branch, Division of Industrial and Medical Nuclear Safety,
NMSS, Mail Stop T8F3.

2800/037-06 COMPLETION SCHEDULE

Irradiator facilities are normally inspected at two-year intervals. The
expected completion schedule for this TI is 24 months from the date of
issuance, to ensure that most irradiators are included in the
implementation of the TI.

2800/037-07 EXPIRATION

This TI remains in effect two years from the date of issuance.

2800/037-08 CONTACT

Questions regarding this TI should be addressed to Michael K.
Williamson, Rulemaking and Guidance Branch, Division of Industrial and
Medical Nuclear Safety, NMSS, at 301-415-6234.

2800/037-09 STATISTICAL DATA REPORTING

No change in entering/charging staff hour expenditures or administrative
effort to the is required for the implementation of this TI during the
two-year period.

2800/037-10 ORIGINATING ORGANIZATION INFORMATION

10.1 [Organizational Responsibility]{.underline}. The Materials Safety
and Inspection Branch, IMNS, NMSS initiated this TI.

10.2 [Resource Estimate]{.underline}. Inspections conducted under this
TI are not expected to require staff hour expenditures exceeding those
required for inspections of these licensees using the current inspection
procedure.

2800/037-11 REFERENCES

NRC Inspection Manual, Inspection Procedure 87122, "Irradiator Programs"

NUREG-1556, Volume 6, "Consolidated Guidance About Materials Licensees,
Program Specific Guidance About 10 CFR Part 36 Irradiator Licenses"

END