ML14226A837

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Industry'S Draft Propostal to Revise Regulatory Guide 8.38 - Attachment
ML14226A837
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Site: Nuclear Energy Institute
Issue date: 06/20/2014
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Nuclear Energy Institute
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Office of Nuclear Regulatory Research
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Industrys DRAFT Proposal to Revise REGULATORY GUIDE 8.38 CONTROL OF ACCESS TO HIGH, TECHSPEC/LOCKED AND VERY HIGH RADIATION AREAS IN NUCLEAR POWER PLANTS Industry Proposal 1C June 20, 2014

REGULATORY GUIDE 8.38 CONTROL OF ACCESS TO HIGH, TECH SPEC/LOCKED AND VERY HIGH RADIATION AREAS IN NUCLEAR POWER PLANTS A. INTRODUCTION In Section 20.1101, "Radiation Protection Programs," of Title 10, Part 20, of the Code of Federal Regulations (10 CFR Part 20), "Standards for Protection Against Radiation," the U.S. Nuclear Regulatory Commission (NRC) requires licensees to develop and implement a radiation protection program appropriate to the scope of licensed activities and potential hazards. To augment that requirement, 10 CFR 20.2102, "Records of Radiation Protection Programs," requires licensees to document those radiation protection programs. An important aspect of such programs at nuclear power plants is the institution of a system of controls that includes procedures, training, audits, and physical barriers to protect workers against unplanned exposures in High and Very High Radiation Areas. In addition, within nuclear power plants Technical Specifications also require specific controls in areas greater than 1000 mrem (10 mSv) in 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />. Toward that end, specific requirements applicable to controlling access to high radiation Areas are in 10 CFR 20.1601, and additional requirements to prevent unauthorized or inadvertent entry into Very High Radiation Areas are in 10 CFR 20.1602. This regulatory guide describes methods that the NRC staff finds acceptable for implementing these requirements.

Appendix A to this guide contains recommended procedures for good operating practices for underwater diving operations in High and Very High Radiation Areas. These practices have evolved, in part, from instances in which proper controls were not implemented. In addition, Appendix B summarizes past experience with Very High and potentially Very High Radiation Areas, so that pertinent historical information is readily accessible.

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B. DISCUSSION The provisions of 10 CFR 20.1601 and 20.1602 specify the requirements through which the NRC intends to prevent exposures in excess of regulatory limits at agency-licensed facilities. This guide complements those requirements by recommending a framework of graded radiation protection procedures to ensure that the controls for access to high and Very High Radiation Areas at nuclear power plants are appropriate to the radiation hazards during both normal operations and abnormal operational occurrences.

Dose rates in areas of nuclear power plants that are accessible1 to individuals can vary over several orders of magnitude. High Radiation Areas, where personnel can receive doses in excess of the regulatory limits in a relatively short time, require special controls. Very High Radiation Areas require much stricter monitoring and controls, because failure to adequately implement effective radiological controls can result in radiation doses that pose a significant health risk.

In some instances, the requirements of 10 CFR 20.1601(a) for access to High Radiation Areas may unnecessarily restrict plant operations by locking High Radiation Areas. Although licensees have the option to control High Radiation Areas with a control device to reduce radiation levels when an individual enters the area, or an alarm to alert the individual and his or her supervisor to an entry into a High Radiation Area, experience has shown that these options have limited practical application at nuclear power plants.

During the initial licensing phase, nuclear power reactors have implemented alternate controls in the Technical Specifications (Tech Spec) as allowed per 10 CFR 20.1601 (c). As such, for purposes of this Regulatory Guide for nuclear power plants, High Radiation, Tech Spec/Locked High Radiation and Very High Radiation Areas are defined as such:

1. High radiation Area is defined as an area, accessible to individuals, in which radiation levels could result in an individual receiving a deep dose equivalent in excess of 100 mrem (1 mSv) in 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> to less than 1000 mrem (10mSv) at 30 centimeters (cm) (11.8 in.) from the radiation source or from any surface that the radiation penetrates.
2. Tech Spec/Locked High Radiation Area2 is defined as an Area, accessible to individuals, in which radiation levels could result in an individual receiving a deep dose equivalent greater than or equal to 1000 mrem (10 mSv) but less than 500 rads (5 Gy) in 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> at 1 meter (3.3 ft)
3. Very High Radiation Area means an area, accessible to individuals, in which radiation levels could result in an individual receiving an absorbed dose in excess of 500 rads (5 grays (Gy)) in 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> at 1 meter (3.3 ft) from a radiation source or any surface that the radiation penetrates.

1 An accessible area is defined as one that can reasonably be occupied by a major portion of an individual's whole body, which is defined in 10 CFR 20.1003, "Definitions."

2 Tech Spec/Locked High Radiation Area is not specifically defined in 10 CFR Part 20, but implemented and defined as part of an alternate control as described in plant Technical Specifications.

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C. REGULATORY POSITION Program Elements In 10 CFR 20.1101, the NRC requires licensees to develop and implement a radiation protection program appropriate to the potential radiation hazards in the given facility. Because of the potential for exceeding regulatory limits in High and Very High Radiation Areas, it is important that licensees have effective programs for controlling access to such Areas. Past experience has shown that inadequate access controls have resulted in instances in which unauthorized personnel entered these Areas.

Licensees' plant procedures and practices should include the following elements: (1) Management, (2)

Procedural and (3) Physical Controls to ensure that personnel are protected in High, Tech Spec/Locked High and Very High Radiation Areas.

1. Management Control Facility management has the responsibility for developing, implementing, and enforcing access control procedures for High, Tech Spec/Locked High and Very High Radiation Areas, including training and communications. It is important to understand that as radiological conditions increase from High Radiation to Tech Spec/Locked High Radiation to Very High Radiation Areas, increased controls (administrative and physical) are necessary to protect workers from inadvertently accessing potentially fatal conditions.

1.1 Training The types of controls required for entry into High, Tech Spec/Locked High and Very High Radiation Areas (including temporary shielding) should be included in both initial and requalification training for radiation workers. Plant Areas that are known to have a potential to become Very High Radiation Areas should be specifically identified.

1.2 Communications Good communication is essential among all departments concerned with entry into High, Tech Spec/Locked High and Very High Radiation Areas to prevent excessive and unwarranted radiation exposures. This communication is especially important among personnel in known potential or existing Very High Radiation Areas, such as reactor cavities, spent fuel transfer Areas, spent fuel pools, and other reactor components and tanks. The access control program should include procedures and provisions for the use of equipment to ensure adequate communication.

The group or department responsible for radiation protection should be notified prior to any entry into a Very High Radiation Areas.

2. Procedural Controls Procedural controls are typically two types: administrative and access controls.

2.1 Administrative Procedures Administrative procedures should address the management oversight and specific control measures needed for entry into High, Tech Spec/Locked High and Very High Radiation Areas. The procedures should include the process for gaining entry to these Areas, such as the control and distribution of keys (where applicable).

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2.2 Access Control Procedures A large facility such as a nuclear power plant can institute appropriate positive access controls through the use of RWPs or procedures. These procedures that establish requirements for control and delegate responsibility to qualified individuals and should establish positive control over each entry by the following:

1. Surveys should be conducted to identify the radiation hazards in the area, and the survey results should be documented.
2. An appropriate level of supervision should determine that exposure of the individual to the hazards is warranted.
3. The nature and extent of the radiation hazards should be communicated to each individual entering the area.
4. Protective measures (e.g., shielding, time limits, protective clothing, monitoring) should be used to protect the individual from excessive or unnecessary radiation exposure.
5. Only authorized individuals should be permitted to enter High Radiation Areas, including documentation of all entries and exits.
6. Placement of alarming dosimeters.

2.3 Timely Surveys Procedures should provide for timely surveys to identify and post with precautionary notices the areas and systems that may become High, Tech Spec/Locked High or Very High Radiation Areas, especially when in-plant changes (e.g., spent fuel transfer operations) could alter ambient radiation levels.

2.4 Activities That Can Greatly Increase Radiation Levels Procedures for activities that can greatly increase in-plant radiation levels (i.e., withdrawal of in-core detectors, thimble tubes, or traversing in-core probes from the reactor) should provide for notification of personnel who are likely to authorize or have access to affected Areas.

2.5 Verification of Physical Controls Licensees should implement procedures to ensure that proper controls for restricting access to High, Tech Spec/Locked High and Very High Radiation Areas are in place and verified at least weekly.

Physical controls should be established per plant Technical Specifications in accordance with specific radiation levels for each area.

Refer to the Tech Spec/Lock High Radiation Area and Very High Radiation Area sections for additional information on verification of locks/locking mechanisms.

3. Physical Controls - Barriers and Barricades 3.1 High Radiation Areas 4

High radiation Area is defined as an area, accessible to individuals, in which radiation levels could result in an individual receiving a deep dose equivalent in excess of 100 mrem (1 mSv) in 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> to less than 1000 mrem (10mSv) at 30 centimeters (cm) (11.8 in.) from the radiation source or from any surface that the radiation penetrates.

3.1.1 Access Controls for High Radiation Areas Each High Radiation Area, as defined in 10 CFR Part 20, should be barricaded3 and conspicuously posted as a High Radiation Area, and entrance thereto should be controlled by requiring issuance of an RWP or equivalent. Individuals trained and qualified in radiation protection procedures (e.g., a health physics technician) or personnel continuously escorted by such individuals may be exempted from this RWP requirement while performing their assigned duties in High Radiation Areas provided that they are otherwise following plant radiation protection procedures, or a general radiation protection RWP, for entry into such high radiation Areas. Any individual or group of individuals permitted to enter such areas should be provided with or accompanied by one or more of the following:

1. a radiation monitoring device that continuously indicates the radiation dose rate in the area;
2. a radiation monitoring device that continuously integrates the radiation dose rate in the area and alarms when a preset integrated dose is received. Entry into such areas with this monitoring device may be made after the dose rates in the area have been determined and personnel are knowledgeable of them;
3. individual qualified in radiation protection procedures with a radiation dose rate monitoring device. This individual is responsible for providing positive radiation protection control over the activities within the area and should perform periodic radiation surveillance at the frequency specified in the radiation protection procedures or the applicable RWP.

Relatively small areas with several discrete High Radiation Areas (i.e., near several valves or components) do not require separate barricades and posting for each if the whole room (or area) is considered a High Radiation Area.

3.2 Tech Spec/Locked High Radiation Areas Tech Spec/Locked High Radiation Areas are those areas that are accessible to personnel and that have radiation levels greater than 1000 mrem (0.01 Sv) but less than 500 rads (5 Gy) at 1 meter (3.3 ft) in 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> from the radiation source, or from any surface penetrated by the radiation, should be provided with locked doors or secured using a locking mechanism (i.e. locked) to prevent unauthorized entry.

3.2.1 Access Controls for Tech Spec/Locked High Rad Areas 3 A barricade can be a rope, ribbon, or other firmly secured, conspicuous obstacle that (by itself or used with physical barriers such as existing walls or hand railings) completely surrounds the area and obstructs entry.

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Individual Tech Spec/Locked High Radiation Areas that are accessible to personnel and that are within large areas where no enclosure exists to enable locking and where no enclosure can be reasonably constructed around the individual area should be barricaded and conspicuously posted. Barriers should be established such that an individual who incorrectly assumes that they have access could not easily circumvent the barrier. Barriers should provide reasonable assurance that they cannot be easily circumvented. A fence that is approximately 6 feet high would normally be adequate to control access to a High Radiation Area at a nuclear power plant. Other barriers, such as training and signage may be used to provide additional barriers as deemed necessary. In any case, determined circumvention of a barrier, using tools such as wire cutters, etc. or an individual willing to violate safe work practices cannot be prevented absolutely. Such circumstances should be addressed with appropriate disciplinary actions.

Openings in physical barriers around a Tech Spec/Locked High Radiation Areas are not required to be controlled as entrances if accessing them requires exceptional measures (unusual or extraordinary actions taken as a means to an end). Examples of areas that do not need to be controlled as entrances are the manway to a tank or vessel that has its cover bolted in place, or an opening in a shield wall that is physically difficult to access without a ladder or mobile platform. The provisions of 10 CFR 20.1601(a)(3) require positive control over each individual entry when access is required to a Tech Spec/Locked High Radiation Area.

Doors should remain locked except during periods of access by personnel under an approved RWP that specifies the dose rates in the immediate work areas and the maximum allowable stay time for individuals in that areas. In lieu of a stay time specification on the RWP, direct or remote continuous surveillance (such as closed circuit TV cameras) may be made by personnel qualified in radiation protection procedures to provide positive exposure control over the activities being performed within the area.

Controls must be established to prevent personnel from being locked inside any High Radiation Areas [10 CFR 20.1601(d)]. Procedural controls must prevent the areas from being locked with personnel inside. If doors are self-locking, personnel must be able to open them from the inside without a key.

If allowed by the plant Technical Specifications, a flashing light may be activated as a warning device whenever the dose rate in such an areas exceeds or is expected to exceed 1000 mrem (0.01 Sv) in 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> at 30 cm (11.8 in.) from the radiation source or from any surface penetrated by the radiation.

3.2.2 Control of Keys and Locked Door Surveillance The shift supervisor or radiation protection manager (or their respective designees) should administratively control the issuance of keys to, and return of keys by, personnel requiring access to Tech Spec/Locked High Radiation Areas.

Each licensee should establish a surveillance program to verify the physical controls for each accessible Tech Spec/Locked High Radiation Area. Surveillance frequency should be at least weekly. In addition, each licensee should also consider periodic preventive maintenance program for the locks. If during a routine surveillance, a Tech Spec/Locked High Radiation Area door is discovered broken due to physical or mechanical failure (not due a human performance event such as door left unlocked or left open) then:

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1. immediately guard door,
2. keep the door guarded until the lock is repaired or replaced or otherwise control this door until problem corrected;
3. verify that no personal are in the area or have entered the area;
4. conduct an extent of condition review of the other doors;
5. repair or replace the door lock expeditiously but within 7 days; and
6. enter the event into the plants corrective action process for tracking and trending.

Note that these occurrences are not normally considered Tech Spec violations for failure to lock the areas as long as there is no a history of similar failures.

3.3 Control Practices for Large High Radiation and Locked High Radiation Areas Controls (e.g. access control and posting) for High Radiation Areas may be established at locations beyond the immediate boundaries of the High Radiation Area to take advantage of natural or existing barriers. For drywells (BWRs) and containments (PWRs), access controls can be established either at the local areas or at a natural entry boundary such as personnel hatches at a drywell or containment. The use of one control point where positive control over personnel entry is exercised, to establish control over multiple High Radiation Areas is acceptable provided the following conditions are met:

1. Control points are established sufficiently close to the High Radiation Area so that adequate supervision of access to the area can be ensured and
2. Required protective measures and other requirements for entering 4the High Radiation Area (e.g. dosimetry, monitoring) are enforced at the control point.

3.4 Very High Radiation Areas Very High Radiation Area means an area, accessible to individuals, in which radiation levels could result in an individual receiving an absorbed dose in excess of 500 rads (5 grays (Gy))

in 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> at 1 meter (3.3 ft) from a radiation source or any surface that the radiation penetrates.

Because of the potential danger of life-threatening overexposures to individuals, extremely tight control must be maintained over any entry to Very High Radiation Areas. According to 10 CFR 20.1602, licensees must institute additional measures as previously described in the High Radiation and Tech Spec/Locked High Radiation Area sections of this document. This is to ensure that an individual is not able to gain unauthorized or inadvertent access to Very High Radiation Areas. To the extent possible, entry should be forbidden unless there is a sound operational or safety reason for entering. Special consideration should be given to areas that become Very High Radiation Areas when the plant changes operational modes, such as shutdowns or startups.

3.4.1 Access Controls for Very High Radiation Areas Entrances to Very High Radiation Areas should be kept locked except during periods when access to the area is required. (See 10 CFR 20.1601(a)(3).) Posting of Very High Radiation Areas is required by 10 CFR 20.1902, "Posting Requirements."

4 Protective measures for access to an area that is not posted and barricaded as a High Radiation Area, but is within a room or area controlled as a High Radiation Area, may be relaxed commensurate with the radiological hazards existing in the area.

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Multiple Very High Radiation Areas may be controlled with one locked entrance to take advantage of natural or existing barriers. For example, several Very High Radiation Areas inside the reactor containment, with the reactor at power, may be controlled by locking the containment access port. However, each Very High Radiation Area within these areas should also be conspicuously posted and barricaded separately. Controls for personnel access to Very High Radiation Areas should be established at the locked entrance.

Authorized entries to Very High Radiation Areas may be monitored by continuous direct electronic surveillance. Unauthorized entries to Very High Radiation Areas inside a pressurized-water reactor (PWR) containment at power can be controlled by locking containment access. However, during authorized entry of the containment at power, electronic surveillance is an acceptable method to ensure that unauthorized entries do not occur into posted and barricaded Very High Radiation Areas within the containment.

3.4.2 Control of Keys to Very High Radiation Areas The following procedures should govern the administrative control of keys to Very High Radiation Areas:

1. Procedures should be established so that (a) requirements for issuance of keys to Very High Radiation Areas are stricter than those for keys to Tech Spec/Locked High Radiation Areas, and (b) the responsible operations and radiation protection supervisors are notified before personnel enter Very High or potentially Very High Radiation Areas.
2. A key for access to a Very High Radiation Areas should unlock only that area.

Master keys that unlock more than one area may be established for use during emergency situations, provided that their distribution is limited and they are not used for normal personnel access.

3.4.3 Radiation Work Permits Entries to Very High Radiation Areas should be controlled by issuance of a specific RWP or equivalent. General, standing, or blanket RWPs should not be used to control entries to Very High Radiation Areas.

3.4.4 Radiation Protection Technician A person entering a Very High Radiation Area should be accompanied to the entryway to that area by a radiation protection technician who can determine the radiation exposure conditions at the time of entry and render assistance if necessary.

3.4.5 Potential Very High Radiation Areas Areas of the plant that are not normally very hazardous during normal plant operations are known to have a high potential for becoming Very High Radiation Areas during certain operational occurrences should be controlled to provide for ready evacuation of the Areas.

For example, the upper drywell in a boiling-water reactor (BWR) may become a Very High Radiation Area if an activated fuel bundle is dropped during fuel handling or a PWR reactor cavity sump can change from a Radiation Area to a Very High Radiation Area as a result of withdrawal of the retractable in-core detector thimble tubes. (See Appendix B.)

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3.4.5.1 Administrative Procedures Administrative procedures should be established to identify these "special" plant areas and ensure that appropriate control measures for potentially Very High Radiation Areas are implemented prior to starting any operation that could create Very High Radiation Areas.

3.4.5.2 Spent Fuel Pools, Reactor Vessels, and Refueling Cavities Because of high radioactivity levels from activation and contamination, materials in the spent fuel pools, reactor vessel, and refueling cavities could create a Very High Radiation Areas when unshielded. These materials are normally covered with more than 3 meters (10 ft) of water and are inaccessible to personnel performing duties above the pool surface. (Diving operations can make the High and Very High Radiation Areas in the pools accessible. Regulatory Position 4.3 below, for guidance on access control of divers.) Therefore, these pool areas do not have to be controlled as High or Very High Radiation Areas solely because of the materials in them, provided that the following criteria are fulfilled:

1. Control measures are implemented to ensure that activated materials are not raised above or brought near the surface of the pool water.
2. All drain line attachments, system interconnections, and valve lineups are properly reviewed to prevent accidental drainage of the water.
3. Controls for preventing accidental water loss and drops in water levels that may create High and Very High Radiation Areas are incorporated into plant procedures.

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3.4.5.3 Procedures for Diving To ensure proper radiological controls, written procedures for any diving operations into pools, tanks, or cavities, or for access to plant components that contain or may contain highly radioactive materials, should be established.

Underwater divers are commonly used for inspections and maintenance in reactor cavities and spent fuel pools. These underwater operations require careful planning, proper work methods, and specific procedures because of the potential for significant exposures from irradiated fuel elements and irradiated reactor components and structures that act as high-level radiation sources.

Appendix A discusses some radiological considerations that should be incorporated into plant procedures for diving operations.

3.5 Temporary Shielding Temporary shielding (i.e., shielding that is not a permanent, unmovable part of the plant's systems or structures) may be used to ensure inaccessibility of a High, Very High, or potentially Very High 9

Radiation Areas. The following guidelines apply to shielding used for the purpose of controlling access:

1. Blankets, bricks, or other portable shielding that could be moved by hand should be secured in place by lock-wire, ties, bolts, or other fasteners that would require a tool to remove. Block walls that are designed into the plant and also provide shielding, or shielded hatches, plugs, or covers that require a hoist or crane to move, are not considered removable by hand.
2. The shielding or shielded access should be posted with an appropriate warning sign, such as "Warning, do not remove. High Radiation levels may result," or "Danger, do not remove. Very High Radiation levels may result."
3. Local audible and visible alarming radiation monitors should be installed to alert personnel if temporary shielding, used to control access to the spent fuel transfer tube or other plant areas of greater than 100 rads/hour (1 Gy) is removed.
4. The facility's routine radiological surveillance program should verify the effectiveness of the temporary shielding and/or (if appropriate) operability of the alarming radiation monitors.

3.6 Cacooning An acceptable method of excluding personnel from areas with dose rates greater than 100 mrem (1 mSv) in 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> is to provide a substantial physical barrier (e.g., chain link fencing) that completely encloses the area and has no openings or portals. This type of control is commonly called "cocooning." Since these areas are not accessible, the 10 CFR Part 20 requirements for access control and posting of High and Very High Radiation Areas do not apply. However, the requirements to instruct the worker on the radiological hazards in these areas are applicable, as specified in 10 CFR Part 19, "Notices, Instructions, and Reports to Workers: Inspection and Investigations."

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D. IMPLEMENTATION NRC Boilerplate REGULATORY ANALYSIS NRC Boilerplate 11

APPENDIX A PROCEDURES FOR DIVING OPERATIONS IN HIGH AND VERY HIGH RADIATION AREAS (1) A special radiation work permit (RWP), or equivalent, should be written to provide detailed requirements for the work.

(2) Diving operations should be continuously observed by qualified radiation protection personnel who have stop-work authority. Clear management guidance on when to exercise this control function should be included in radiation protection and diving procedures. (See the additional discussion on diving in Appendix B.)

(3) The locations of the fuel assemblies and other irradiated objects that produce dose rates greater than 1 rem (0.01 Sv) per hour at their surface should be documented and made known to the divers.

(4) Radiation surveys of diving areas should be conducted before all diving operations. Those pre-job surveys should be conducted using two independent radiation survey instruments. The diver may also perform confirmatory surveys of the work Areas, provided that the diver is properly trained to perform such surveys.

If irradiated fuel or other highly radioactive objects are moved, an underwater survey should be conducted before any diving operation resumes. A survey map of the diving areas should be prepared and updated to reflect the current status.

(5) When practical, physical barriers should be provided to prevent divers from accessing irradiated fuel elements and other high radiation items or areas. Each diver should be equipped with a safety line and continuous voice communication with surface personnel. Emergency procedures for diver rescue should be provided and understood by everyone involved in the diving operation.

(6) Divers should be equipped with a calibrated dosimeter that will function and provide an alarm underwater.

This dosimeter should be checked for operability each day before diving operations begin. Each diver should also be equipped with a remote-readout radiation detector that is continuously monitored by radiation protection personnel.

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13 APPENDIX B EXPERIENCE WITH VERY HIGH AND POTENTIALLY VERY HIGH RADIATION AREAS The following NRC documents provide information concerning past incidents in high and Very High Radiation Areas and discuss means for preventing their recurrence. They are listed here so that pertinent historical information is readily accessible:

1984/in84019.html.

1987/in87013.html.

1988/in88063.html.

Information Notice 88-79, "Misuse of Flashing Lights for High Radiation Areas Controls," October 7, 1988, http://www.nrc.gov/reading-rm/doc-collections/gen-comm/ info-notices/1988/in88079.html.

Information Notice 90-33, "Sources of Unexpected Occupational Radiation Exposure at Spent Fuel Storage Pools," May 9, 1990, http://www.nrc.gov/reading-rm/doc-collections/gen-comm/info-notices/ 1990/in90033.html.

Information Notice 95-56, "Shielding Deficiency in Spent Fuel Transfer Canal at a Boiling-Water Reactor," December 1 1, 1995, http://www.nrc.gov/reading-rm/doc-collections/ gen-comm/info-notices/1995/in95056.html.

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Information Notice 96-25, "Traversing In-Core Probe Overwithdrawn at LaSalle County Station, Unit 1," April 30, 1996, http://www.nrc.gov/reading-rm/doc-collections/gen-comm/ info-notices/1996/in96025.html.

Information Notice 97-68, "Loss of Control of Diver in a Spent Fuel Storage Pool," September 3, 1997, http://www.nrc.gov/reading-rm/doc-collections/gen-comm/ info-notices/1997/in97068.html.

These documents are available electronically through the NRC's public Web site (as indicated above). They are also available for inspection and copying for a fee from the NRC's Public Document Room, located at 11555 Rockville Pike, Rockville, Maryland. The PDR's mailing address is USNRC PDR, Washington, DC 20555-0001. The PDR can also be reached by telephone at (301) 415-4737 or (800) 397-4205, by fax at (301) 415-3548, and by email to PDR@nrc.gov.

In addition, in January 1983, the Electric Power Research Institute, Nuclear Safety Analysis Center (NSAC),

published a report, entitled "Residual Heat Removal Experience Review and Safety Analysis: Pressurized Water Reactors" (NSAC-052), which provides additional information on past incidents.

Some of the areas mentioned in the above documents have the potential to become High and Very High Radiation Areas during certain periods of operation (most frequently during refueling outages). Table B-1 lists potential radiation fields for certain operations; these are general ranges, and actual numbers may be higher or lower because of plant-specific factors.

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Table B-1 Potential Radiation Fields General Exposure Ranges Spent fuel transfer tube 10,000-50,000 rads/hr (100-500 Gy/hr)5 Letdown IX/filter 1,000-10,000 rads/hr (10-100 Gy/hr)

Spent fuel (in pool) 100,000-1,000,000 rads/hr (1,000-10,000 Gy/hr)

Radwaste resin tank 5,000 rads/hr (50 Gy/hr)

Traversing in-core probe detectors (TIPS) and cables, 1-100,000 rads/hr (0.01-1,000 Gy/hr) source and intermediate range monitor detectors and cables (SRMs, IRMs) 6 Reactor cavity with thimbles withdrawn 200-2,000 rads/hr (2-20 Gy/hr)

Thimbles 50,000 rads/hr (500 Gy/hr)

Reactor cavity (in-core) >1,000 rads/hr (>10 Gy/hr)

Steam generator channel head 7 10-40 rads/hr (0.1-0.4 Gy/hr)

Without proper controls and monitoring, personnel entering these areas when the indicated radiation fields are present could receive radiation exposures with severe or life-threatening consequences.

A study of the above documents indicates generic reasons for repeated incidents. In general, improper entry into these areas results from a lack of awareness, indicating insufficient training and administrative controls. Some of the causes are discussed below.

Entry Into Reactor Cavities When In-Core Detectors Are Withdrawn During refueling or maintenance, the retractable in-core detectors and associated thimble tubes are sometimes withdrawn from the reactor. While in the reactor core, parts of the detector system (such as the thimble tubes) become highly radioactive. These parts can create radiation fields within the reactor cavity where annual occupational dose limits can be exceeded within a few seconds. These extremely hazardous areas can present life-threatening radiation situations in which acute exposures, sufficient to cause serious radiation injury, are possible after just a few minutes of exposure. This hazard is compounded by limited visibility and access to equipment within the reactor cavity. The cavity is also a hostile physical environment in which accidents and mishaps can occur.

In the vicinity of the thimbles, general Areas dose rates can be greater than 2,000 rads per hour (20 Gy per hour), with dose rates at the surface of the guide tubes as high as 20,000-40,000 rads per hour (200-400 Gy per hour).

Acute exposures to these high dose rates are sufficient to cause clinical radiation injury effects (or possibly death) within just a few minutes [e.g., 2,000 rads/hr or 30 rads/min (20 Gy/hr or 0.3 Gy/min)]. (See Figure B-1.)

5 This is the dose rate during spent fuel transfer.

6 These doses vary considerably depending on the time after withdrawal from the core. Immediately upon withdrawal, a dose rate of >10,000 rads/hr (100 Gy/hr) may be experienced, while decay can reduce the contact dose rates to 1-10 rads/hr (0.01-0.1 Gy/hr) after about 3 days.

7 Although this is not a Very High Radiation Area, it is important because it is frequently accessed by personnel.

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17 In the past, personnel from the operations departments at several plants have entered the reactor cavity without radiation work permits, adequate surveys, or knowledge of the condition of the retractable in-core detectors and their thimble tubes. Personnel have bypassed the lock systems and ignored posted warning signs regarding the special conditions required for entry. These personnel have included managers, shift engineers, 18

shift supervisors, reactor operators, and health physics technicians. These incidents have resulted in overexposures exceeding the NRC's established regulatory limits and several near overexposures.

Fuel Movement in BWR Drywells During certain spent fuel handling operations, very high dose rates can exist in BWR drywells. All drywell containment types (Mark I, II, and III) lack complete shielding. Fuel handling must be controlled to prevent potentially fatal exposure to 4drywell6 workers from mishaps with irradiated fuel. Unshielded irradiated fuel can create radiation fields of 10 to 10 rads per hour (102 to 104 Gy per hour) at a distance of 30.5 cm (1 ft). Figure B-2 shows dose rates in several drywell areas resulting from spent fuel in various configurations.

The NRC has conducted reviews of the radiological controls for BWR drywells during spent fuel movement, which included licensees' use of temporary shielding for spent fuel transfer to the storage pool (see Figure B-3), operational considerations (e.g., restricting access to the upper drywell or evacuation procedures for the drywell during fuel movement), and employee training. These reviews identified the following conditions:

(1) Personnel were not aware of the hazards to a worker in the drywell resulting from a dropped spent fuel element.

(2) Personnel were not aware of the special shielding requirements.

(3) Radiological controls, procedures, and personnel training needed improvement.

(4) There was a lack of communication between fuel operations and personnel at radiological control points.

TOWARD SPENT FUEL POOL Figure B-3 Portable Radiation Shield

Divers in the Spent Fuel Pool and Reactor Cavity Divers are used for an increasing number of maintenance and inspection tasks. The operations these individuals perform require careful and thorough planning. The use of proper underwater work techniques can result in substantial time savings and reductions in radiation doses.

The gear that divers wear makes their out-of-water movements awkward and makes seeing and hearing more difficult, thereby hindering communications. Control of a diver's location in the pool is important to keep the diver away from areas of High Radiation levels.

Careful planning and execution of divers' work in the spent fuel pool, reactor cavity, and reactor 4

vessel 6

and piping are 2

extremely 4

important, as a single spent fuel element can create radiation fields of 10 and 10 rads per hour (10 and 10 Gy per hour) at close proximity. Other irradiated objects in the pool or cavity can produce dose rates from ten to hundreds of rads per hour.

Past experience shows that surveys and radiation work permits have sometimes been inadequate for the special nature of the divers' work environment. Continuous-readout dosimeters and dose rate survey instruments have not been widely used. Dosimeters with alarms have failed for lack of proper controls and checks of instruments. Dose rate monitoring devices that warn of unexpected changes in dose rates in the work Areas have not been used. Procedures detailing special precautions for diving operations in these areas have also been inadequate in some cases. Visibility, lighting, and performance of underwater survey instrumentation in the fuel pool have been poor.

Loss of Water from the Fuel Pool, Fuel Transfer Canal, and Reactor Cavity Complete or partial loss of water from the spent fuel pool, fuel transfer canal, or reactor cavity can result in Very High Radiation Areas. In some instances, a refueling cavity water pneumatic seal and a transfer canal pneumatic seal have failed, causing a rapid drop in the water level in the spent fuel pool. These large water losses can expose spent fuel in the fuel pool or uncover other highly radioactive objects in the fuel pool (such as irradiated control rod blades and neutron detectors) within a few minutes. These large water losses could also result in high radiation levels from components that have been suspended at insufficient depth in the spent fuel pool.

Other mechanisms that can cause water losses in the spent fuel pool, fuel transfer canal, and reactor cavity include certain misalignments of valves in the residual heat removal system while the reactor is in the shutdown cooling mode (assuming shutdown cooling is in use when the cavity is filled), leaking steam generator nozzle dams, and slow-draining lines attached to the refueling cavity.

Resin Tanks, Systems, and Chemical Decontamination Resin tanks may accumulate large inventories of radionuclides from the processing of various coolants or wastes. Resins may flow through piping in the reactor facilities because of improper valve lineups, malfunctions, etc., and may result in new High Radiation Areas.

Chemical decontamination of systems may result in movement of large quantities of radioactive materials. Activities in these areas must be carefully observed because of the potential for the areas to become Very High Radiation Areas.

Other Very High Radiation Areas Portions of the reactor piping (such as valves and loops) may become collection points for radionuclides over time. Activities in these areas must be carefully observed because of the potential for the areas to become Very High Radiation Areas.

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