Lesson Plan Templategonuke.org/wp-content/toolkits/Radiation Protection/chscc... · Web viewAny items removed from the reactor vessel or internals can create an airborne problem if

ACADs (08-006) Covered

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Description

Supporting Material

Radiological Hazards Associated with

Pressurized Water

HPT001.014GRevision 0Page 1 of 33

NUCLEAR TRAININGTRAINING MATERIALS COVERSHEET

RADIOLOGICAL PROTECTION TECHNICIAN INITIAL TRAININGPROGRAM SYSTEMS TRAINING HPT001COURSE

COURSE NO.

PRESSURIZED WATER REACTOR RADIOLOGICAL HAZARDS HPT001.014GLESSON TITLE LESSON PLAN NO.

INPO ACCREDITED YES X NO

MULTIPLE SITES AFFECTED YES X NO

PREPARED BY C. Daphne Stephens

______________________________________ Signature / Date

PROCESS REVIEWGale Blount

______________________________________ Signature / Date

LEAD INSTRUCTOR/PROGRAM MGR. REVIEWRoy Goodman

______________________________________ Signature / Date

PLANT CONCURRENCE - BFN ______________________________________ Signature / Date

PLANT CONCURRENCE - SQN ______________________________________ Signature / Date

PLANT CONCURRENCE- WBN ______________________________________ Signature / Date

Receipt Inspection and Distribution: Training Materials Coordinator /Date

Standardized Training MaterialCopies to:

TVA 40385 [NP 6-2001] Page 1 of 2


NUCLEAR TRAINING

REVISION/USAGE LOG

REVISIONNUMBER

DESCRIPTIONOF CHANGES

DATE PAGESAFFECTED

REVIEWED BY

0 Initial Issue All C. Daphne Stephens

TVA 40385 [NP 6-2001] Page 2 of 2


I. PROGRAM: Radiological Protection Technician Initial Training

II. COURSE: Systems Training

III. LESSON TITLE: Pressurized Water Reactor Radiological Hazards

IV. LENGTH OF LESSON/COURSE: 2 hours

V. TRAINING OBJECTIVES:

A. Terminal Objective:

Upon completion of the Nuclear Plant Systems Orientation for pressurized Water Reactors course, the participants will demonstrate their knowledge of Sequoyah and Watts Bar systems, by scoring >80% on a written examination. The examination may be based on the enabling objectives in this lesson only, or it may be part of a comprehensive examination covering multiple lesson plans.

B. Enabling Objectives:

1. Explain radiological conditions that might be present in a high radiological

hazard system.

2. List systems of high radiological hazard.

3. Explain radiological conditions that might be present in a medium radiological

hazard system.

4. List systems of medium radiological hazard.

5. Explain radiological conditions that might be present in a low radiological

hazard system.

6. List systems of low radiological hazard.

7. Identify sources of radiological hazards at pressurized water reactors.

8. Identify reactor accident categories and potential radiological consequences of

each.


VI. TRAINING AIDS:

A. Whiteboard and markers

B. Computer, projector, screen, and associated software

VII. TRAINING MATERIALS:

A. Appendices

1. Terms and Definitions

2. Summary of Operating Experience, OE 10579

3. Summary of Licensee Event Report, LER 84-016-00

B. Handouts

1. Handout 1 - Sequoyah ALARA Planning Reports (SQN APR)

2. Handout 2 - Sequoyah Visual Survey Data System Maps

VIII. REFERENCES:

A. Bevalacqua, Joseph John, Wisconsin Electric Power Company, Contemporary Health Physics: Problems and Solutions. John Wiley & Sons. New York, 1995.

B. INPO ACAD 93-008, Guidelines for Training and Qualifications of Radiological Protection Technicians. August, 1993.

C. TVAN Standard Programs and Processes, SPP-5.1, Radiological Controls, Revision 5, October 21, 2003.


IX. INTRODUCTION:

The field of health physics is concerned with protecting the health and safety of the public,

including plant workers, from a wide variety of radiation environments. These

environments include external radiation sources as well as internal sources of radiation.

The situation is often complicated by the occurrence of mixed radiation fields.

While nuclear power plants are designed to minimize radiation exposure and nuclear

power plant have established procedures and controls to protect personnel from radiation,

there are some risks involved. Health physics personnel must have an understanding of

the risks associated with plant systems and components to minimize these risks.

This lesson will give a general overview of the radiological hazards, defined in Appendix

1, associated with various plant systems under normal conditions of operation. It is not

possible to address the potential radiological hazards that could exist during emergency or

accident conditions; therefore, this lesson will only provide a general overview of accident

conditions.

In addition to the material covered in this lesson, students are encouraged to seek

historical survey data available from the Visual Survey Data System and from ALARA

planning reports to gain more knowledge about the radiological hazards at pressurized

water reactors.


X. LESSON BODY: INSTRUCTOR NOTES

A. High Radiological Hazard Systems

1. High radiological hazard systems are systems

which have, either individually or in combination,

any of the following:

a. high radiation

b. high contamination

c. hot particles

d. high levels of airborne radioactivity

Objective 1

2. High radiological hazard systems include:

a. reactor vessel and internals

b. fuel and fuel handling system

c. reactor coolant system

d. incore thermocouples

e. traveling incore probes

f. chemical and volume control system

g. rod control system

Objective 2

3. Reactor Vessel and Internals

a. The reactor vessel and internals present a

high radiological hazard primarily from high

radiation levels.

b. Dose rates from the reactor vessel or

internals could be several hundred rem/hr.

Water is used to provide shielding.

Appendix 2



c. High contamination levels and hot particles,

including fuel fleas, can be expected on tools

and other items that have contacted the

reactor vessel or internals.

d. Any items removed from the reactor vessel

or internals can create an airborne problem

if allowed to dry out.

Fuel fleas can read

several hundred rem/hr.

Items are generally

sprayed down, wiped

off, and wrapped.

4. Fuel and Fuel Handling System

a. The fuel presents a high radiological hazard

due to the extremely high dose rates

associated with spent reactor fuel.

b. Radiation levels from spent fuel bundles may

read thousands of rem/hr.

c. Fuel handling tools and equipment have very

high contamination levels and have the

possibility of having hot particles.

d. Tools and fuel handling equipment may

present a significant airborne radiological

hazard if improperly controlled.

e. Fuel is handled underwater and with

extended tools.

Appendix 3

High contamination on

the tools may get

dispersed in air.



5. Reactor Coolant System

a. The reactor coolant system contains

components that have high radiation levels.

b. Unlike the reactor vessel and internals or the

fuel and fuel handling system where water

is provided for shielding and where

extended handling tools are used, reactor

coolant system component work usually

requires a “hands on” approach.

Tens of rem/hr

Appendix 4

c. All components of the reactor coolant

system can be expected to have high

contamination.

d. All components of the reactor coolant

system can have hot particles.

e. Leaks from the reactor coolant system or

maintenance activities on reactor coolant

system components can result in the spread

of contamination and the generation of

airborne radioactivity.

Have students identify

the major components.

Discuss FME controls.

Discuss use of HEPAs.

6. Incore Thermocouple Monitoring System

a. The thermocouples themselves could be a

high radiological hazard; however, they

stay in the reactor internals.

They are disconnected

each refueling outage,

but never removed.



7. Traveling Incore System

a. The incore probes are a high radiological

hazard due to extremely high radiation

levels.

b. Dose rates associated with the incore probes

can be thousands of rem/hour.

Appendix 5

c. Maintenance activities, such as guide tube

cleaning, can cause high contamination and

result in airborne radioactivity.

d. Any foreign objects or materials can be

highly activated and present a dose hazard.

Discuss foreign objects.

8. Chemical and Volume Control System

a. The chemical and volume control system

is, for the most part, a high radiological

hazard system.

b. There are some components of the CVCS

that present significantly high radiation

levels.

(1) The volume control tank is a locked

high radiation area when the plant is

operating.



(2) The filters and demin beds for the

CVCS may read several hundred

Rem/hr.

Appendix 6

Appendix 7

(3) The regenerative heat exchanger,

letdown heat exchanger, and excess

letdown heat exchanger are locked

high radiation areas.

c. Other CVCS components, such as charging

pumps and piping, seal water injection, and

letdown orifices have low to medium

radiation levels.

d. System breaches of the CVCS components

require air sampling and radiation surveys

for both beta and gamma.

9. Rod Control System

a. The rod control system itself is not a

radiological hazard system, but is considered

a high radiological hazard because of the

radiation dose rates from the reactor head.

b. The control rods stay in the fuel assembly

and are moved during refueling outages as

a part of the fuel assembly.



B. Medium Radiological Hazard Systems

1. Medium radiological hazard systems are systems

which have, or could potentially have, either

individually, or in combination any of the following:

a. radiation

b. contamination

c. hot particles

d. airborne radioactivity

Objective 3

2. Medium radiological hazard systems include:

a. Reactor Vessel Level Indication System

b. Nuclear Instrumentation System – Excore

c. Liquid Radwaste System

d. Residual Heat Removal System

e. Emergency Core Cooling System

Objective 4

3. Reactor Vessel Level Indication System (RVLIS)

a. The reactor vessel level indication system

piping contains reactor coolant.

b. The system is a medium radiological hazard

system because of high contamination

levels.



c. Radiation levels associated with the reactor

vessel level indication system are low due to

the small diameter piping; however, due to

the location of RVLIS components in close

proximity to high radiation fields, work on

this system can result in personnel exposure.

Example: RVLIS

work in upper

containment puts the

workers near Rx head.

4. Nuclear Instrumentation System – Excore

a. The excore detectors are considered a

medium radiological hazard system because

they are located in the bottom of the reactor

cavity.

b. If the gaskets that seal the covers over the

excore detectors have leaked, there will be

high contamination levels.

c. Radiation levels from the detectors are

lower than background dose rates in the area.

5. Liquid Radwaste System

a. The liquid radiation system is a medium

radiological hazard system; however the

individual components in the system may

range from very low levels to very high

levels.



b. The reactor coolant drain tank and the

tritiated drain collector tank are generally

locked high radiation areas.

c. Components such as the hold up tanks and

the floor drain collector tank are usually

radiation or high radiation areas.

d. The monitor tank and the cask decon

collector tank are very low levels and are

usually well below the limits for a radiation

area.

e. Contamination levels associated with the

liquid radwaste system, like the tanks, vary

from very low levels to high levels.

f. Any breach of the liquid radwaste system

should include beta and gamma radiation

surveys, contamination surveys, and air

sampling.

g. Dose rates and contamination levels from

the portable Rad DI system can be high

around the filter vessels and the pressure

vessels which contain the ion exchange

media can be high.



h. Hot particles may be present in the liquid

radwaste system.

i. Floor drain covers might be contamination

areas and if the covers are removed, expect

contamination inside the drain.

6. Residual Heat Removal System

a. The residual heat removal system is a

system that presents medium radiological

risks.

b. The residual heat removal system is not often

used; however, during times of system

operation high dose rates and localized hot

spots may be present.

c. The RHR system takes a suction from the

reactor coolant system, so any system breach can result in high contamination

levels and hot particles may be found.

d. During times of plant operation, when the

RHR system is not in service the dose rates

typically create a radiation area around the

major system components.



e. When the RHR system is in service, expect

high radiation around the major system

components and piping.

f. Any breach of the RHR system may cause

airborne radioactivity.

7. Emergency Core Cooling System

a. The emergency core cooling system is a

medium radiological hazard system.

b. Components that make up the emergency

core cooling system may be extremely low

radiological hazard, such as the refueling

water storage tank, but may present a

medium radiological hazard due to the

component location, such as cold leg

accumulators which are located inside

containment.

c. The emergency core cooling system also

utilizes components from other systems,

such as RHR system pumps and CVCS

system pumps.



d. If accident conditions existed that required

use of the emergency core cooling system,

radiological hazards associated with the

system could be extremely high, depending

on the accident severity.

C. Low Radiological Hazard Systems

1. Low radiological hazard systems have little potential

for radiological hazards, or else, the radiological

hazards present are low level.

2. Low radiological hazard systems have:

a. low radiation levels

b. low level contamination

c. little possibility for airborne radioactivity

Objective 5

3. Low radiological hazard systems include:

a. ice condenser system

b. containment combustible gas control

c. containment purge system

d. ventilation and gas treatment

e. radiation monitor system

f. gaseous radwaste system

g. containment spray system

h. component cooling system

Objective 6



4. Ice Condenser System

a. There are no radiological hazards from the

ice condenser system itself; however, the ice

condenser is located inside containment.

b. There are low levels of radiation in the lower

plenum of the ice condenser when the plant

is shut down and high radiation in the lower

plenum when the plant is operating.

Upper plenum of the

ice condenser has only

low radiation levels,

even at 100% power.

c. There are low levels of contamination in the

ice condenser that has been tracked in from

other areas of containment.

d. The airborne radioactivity in the ice

condenser will be same as containment.

May also find hot

particles

5. Containment Combustible Gas Control

a. The containment combustible gas control

system itself does not cause any radiological

hazards.

b. Components of the system are located inside

containment; therefore, there may be

contamination in the area, radiation, and the

airborne radioactivity will be the same as

the general containment airborne

concentration.



6. Containment Purge System

a. The containment purge system filters the

containment air before it is exhausted.

b. The filters will have low levels of radiation

and low levels of contamination.

c. There is the potential for low levels of

airborne radioactivity inside the filter

housing during filter changeout.

7. Ventilation and Gas Treatment Systems

a. The auxiliary building gas treatment system

filters the auxiliary building air before it is

exhausted.

b. The ABGTS filters have low levels of

radiation and low levels of contamination.

c. There is the potential for low levels of


housing during filter changeout.

d. The auxiliary building ventilation system

supplies the auxiliary building ventilation

during normal operations and does not

pose any radiological hazards.



e. The emergency gas treatment system is a low

radiological hazard because it is normally

used only for annulus vacuum control.

f. The EGTS filters have low levels of

radiation and low levels of contamination.

g. There is the potential for low levels of


housing during filter replacement.

Use during an

accident would make

high hazard system.

8. Radiation Monitoring System

a. Process monitors, either in-line or off-line,

actually have a small amount of the effluent

flowing through the detector.

b. Process monitors systems of radiological

concern will have some contamination and

might have radiation.

c. Area radiation monitors and continuous air

monitors might be located in areas that some

radiological hazards.

9. Gaseous Radwaste System

a. The gaseous radwaste system poses little

radiological hazard because the decay tanks

are located in a vault under the floor and not

normally accessed.

Any system leakage

could pose a more

significant hazard.



b. Components of the gaseous radwaste system,

such as, the waste gas compressors will have

low levels of radiation and low levels of

contamination.

c. Leakage from the gaseous radwaste system

can result in airborne radioactivity.

10. Containment Spray System

a. The containment spray system poses little

radiological hazard.

b. Water circulated through the system for

pump testing has left the system with low

levels of contamination.

11. Component Cooling System

a. The component cooling system itself should

be free of any radiological hazards.

b. Any leakage of components cooled by the

system could result in low levels of

contamination.

c. The heat exchangers for the component

cooling are located in the same room as the

residual heat removal heat exchangers.

Radiation or high

radiation



D. Health Physics Hazards

1. Health physics hazards at pressurized water

reactors include a wide variety of issues.

2. Hazards include:

a. buildup of activity on filters

b. buildup of activity on demin beds

c. activation products

d. fission products

e. fuel element cladding failures

Objective 7

f. hot particles

g. reactor coolant system leakage

h. airborne radioactivity

i. leakage from radiological systems

E. Reactor Accidents

1. Reactor accidents may take a variety of forms, but

the most radiologically significant events will

involve core damage that could lead to the potential

of radioactive releases to plant areas and to the

environment.

2. Other events are less severe, but have a higher

chance of happening.

3. Reactor accidents are classified into broad

categories.



4. Reactor accident categories include:

a. Loss of Coolant Accidents, LOCA

(1) Reactor cooling water is reduced or

lost and the fuel begins to heat up.

(2) May be caused by:

(a) Pipe or line rupture

(b) Seal failure

(c) Leaks in piping, valves or

components

Objective 8

(3) Severe LOCA will result in fuel

melting or fuel cladding damage.

(4) Breaches in cladding will release

fission products into the reactor

coolant.

b. Steam Generator Tube Rupture, SGTR

(1) If a steam generator tube ruptures, the

barrier between the primary and the

secondary side is lost.

(2) The secondary side of the plant will

become contaminated.



c. Fuel Handling Accidents, FHA

(1) Spent fuel contains fission products.

(2) During fuel movement, accidents can

damage the cladding and lead to the

release of radionuclides into the

auxiliary building.

d. Waste Gas Decay Tank Rupture, WGDTR

(1) Gas decay tanks store fission gases

and permit their decay prior to release

to the environment.

(2) Failures of the tank, valves, or

associated components will release

fission gases into the auxiliary

building.

5. An accident might result in emergency equipment

being placed in service and normal flow paths may

be changed.

(1) Radiation levels from piping and components

can increase greatly.

(2) Airborne radioactivity in plant general areas

can increase greatly.


XI. SUMMARY:

This lesson has covered the general radiological hazards associated with various plant

systems, under normal conditions of operation. Experience and on-the-job training at

the plant sites will greatly enhance the student’s understanding of the radiological hazards

from each system.


Appendix 1

Terms and Definitions

Airborne Radioactivity Area - A room, enclosure, or area in which airborne radioactive materials, composed wholly or partly of licensed material, exist in concentrations - (1) in excess of the derived air concentrations specified in Appendix B to 10 CFR 20, or,(2) to such a degree that an individual present in the are without respiratory protective equipment could exceed, during the hours an individual is present in a week, an intake of 0.6 percent of the annual limit on intake or 12 DAC-hours.

Contaminated Area - A radiologically controlled area in which uncontained, removable radioactive material (contamination) is present in excess of:

20 dpm/100 cm2 Alpha1000 dpm/100 cm2 Beta/Gamma

High Radiation Area – An area, accessible to individuals, in which radiation levels from radiation sources external to the body could result in an individual receiving a dose equivalent in excess of 100 mrem in 1 hour at 30 centimeters from the radiation source or 30 centimeters from any surface that the radiation penetrates.

Hot Particle - A single discrete object (particle) generally difficult to see (usually <100 micron) with the naked eye, and at least 0.1 microcuries of radioactivity. It is either an activated corrosion/wear product or fuel fragment with high specific activity. For the purpose of an approximate field calculation, any discrete particle surveyed with a standard frisker probe (HP-260, HP-210, etc.) and found to have levels of greater than or equal to 20,000 cpm, shall be considered a hot particle.

Radiation Area – An area, accessible to individuals, in which radiation levels could result in an individual receiving a dose equivalent in excess of 5 mrem in one hour at 30 cm from the radiation source or from any surface that the radiation penetrates.

Very High Radiation Area - An area, accessible to individuals, in which radiation levels from radiation sources external to the body could result in an individual receiving an absorbed dose in excess of 500 rads in 1 hour at 1 meter from a radiation source or 1 meter from any surface that the radiation penetrates.


Appendix 2

Summary of OE 10579

Plant: Farley Unit 2

Date: November 23, 1999

Title: Crane Operator Received Higher Than Planned Radiation Dose

While moving the reactor vessel lower internals during a refueling outage, the crane operator received a radiation dose higher than planned. A laser/camera system was in place to monitor the elevation of the internals and a mini-sub camera was to be used as abackup to the laser system. During the move, the laser/camera system failed; however the internals move continued. Health physics personnel noticed the dose rates increasing to higher than expected and it was determined that the internals package was higher out of the water than expected. Rather than immediately lowering the internals, it was decided to move the internals toward the reactor vessel, lowering the load as the move progressed. The move was completed and dose rates returned to normal.The polar crane operator received 671 mrem whole body dose. The limit specified on the radiation work permit was 500 mrem. The expected dose for the crane operator was 300 mrem.

Causes: equipment failure, lack of supervisory oversight, poor communication, poor job scope delineation, inadequate pre-job brief, and lack of contingency planning. After the event, it was determined that the mini-sub camera operator did not understand his role as backup to the laser/camera system for monitoring internals elevation.

Discuss potential for similar event at TVA nuclear plant.

Discuss methods to prevent similar event.

When higher than expected dose rates were noticed, what immediate actions should the health physics technicians take?


Appendix 3

Summary of LER # 84-016-00

Plant: Sequoyah Unit 1

Date: February 25, 1984

Title: Auxiliary Building Ventilation Isolation

A high radiation alarm was actuated which caused an auxiliary building isolation to occur. A vacuum cleaner was pulled out the fuel transfer canal, after cleanup of contamination in the canal. The fuel transfer canal was being cleaned prior to beginning refueling operations.The radiation level of the vacuum cleaner was 12 rem per hour on contact.

Discuss significance of auxiliary building isolation, ABI.

Discuss how to prevent event.

What was the likely cause of the high dose rates on the vacuum cleaner?


Appendix 4

Summary of SER 32-86

Plant: Connecticut Yankee

Date: July 23, 1986

Title: Exposure of Worker Above Federal Radiation Dose Limits

Employee performing primary side steam generator repairs received a cumulative quarterly radiation dose of 3.3 Rem resulting from deficient radiation dose controls, improper stay time estimates, and inadequate monitoring of dose during the job.Steam generator workers were viewed on remote television monitors and directed by headset phones, thus permitting workers to perform tasks alone. Work was proceeding on two steam generators at the same time to expedite outage completion. A single radiation protection technician team was controlling both steam generator jobs.The pre-task (move ventilation duct and install video camera) discussion was limited, because the HP team supervisor presumed the worker was experienced.The worker’s remaining dose allowance was 880 mrem. The HP team supervisor determined the stay time for the worker by using the exposure time and records of another worker who had performed what was thought to be similar work. Direct calculations of the stay time from the radiation survey data were not performed. The available radiation survey was not clear as to the exact location of measurements taken outside the steam generator. The HP technicians on shift did not perform their own survey of radiation levels on the steam generator platform to verify their understanding of the radiation conditions.The worker wore two direct reading dosimeters and a TLD on his head and another set on his chest. Both sets were inside the plastic suit and bubble hood. In addition, a direct reading dosimeter was taped on top of his bubble hood so that dose could be easily read. For an hour and a half, the worker was on the steam generator platform moving the ventilation ducting from the hot leg to the cold leg side of the steam generator. This included two entries into the steam generator manways, up to the waist for 20 to 25 seconds each. The HP supervisor directed the worker to have the direct reading dosimeter read by a HP helper. The HP helper discovered that the direct reading dosimeter was missing.The HP supervisor consulted with a technician and they decided the loss of the direct reading dosimeter did not require the immediate evacuation of the worker. They concluded the worker could continue for another hour. The worker installed and adjusted a video camera in the steam generator hot leg. The worker completed the task and exited. The HP supervisor read the worker’s direct reading dosimeter and discovered that the worker had received 1700 mrem to his head and 800 mrem to his chest. The 1700 mrem whole body combined with the worker’s previous exposure of 1620 mrem for the quarter exceeded the federal limit of 3 Rem/quarter.

Discuss event causes and prevention.


Appendix 5

Summary of IE 86-107

Recurring event: Where workers enter the reactor vessel sump room (keyway) while the retractable incore detector thimbles were withdrawn. With the thimbles retracted, radiation levels of thousands or roentgens per hour (R/hr) can exist in the cavity beneath the reactor vessel. Between 1872 and December of 1986, 11 unauthorized entries into pressurized water reactor cavities with the retractable incore detector thimbles withdrawn occurred, leading to 6 personnel overexposures.

Information on related events can be found: INPO SOER 85-3IE Information Notice 84-19 IE Information Notice 82-51 IE Circular 76-03

On March 30, 1986, at Salem Generating Station Unit 1, the shift supervisor directed the containment equipment operator to the reactor vessel sump to check for water leaks through the inflatable cavity seal as the refueling cavity was being filled. The equipment operator, accompanied by a HP technician, attempted to enter the locked entrance door to the seal table room. The high radiation exclusion key did not open the door (wrong key) so the equipment operator jammed the door and entered the seal table room. They began a descent down the ladder with the HP technician in the lead taking radiation survey readings. When the radiation level indicated 3 R/hr, the HP technician stopped the entry, terminated the leak inspection, and both personnel exited the area.

Event causes:

The shift supervisor who directed the entry knew the thimbles were withdrawn, but did not know the thimbles presented a significant radiological hazard. The shift supervisor had checked to ensure that the movable incore detectors were safely stored.

Radiation levels of thousands of R/hr are possible within a few feet of the thimbles.

The containment HPs and operation personnel generally understand the thimble hazards, but were not informed by shift management that thimbles had been withdrawn.

Procedures for installing safety tags, high radiation key control, and the operating procedure for filling the reactor refueling cavity apparently were not followed.

Irradiated components can create radiation fields where occupational dose standards can be exceeded in < 1 minute. These extremely hazardous areas can present life threatening radiation situations where acute exposures, sufficient to cause serious radiation injury, are possible within just a few minutes exposure.

Discuss event prevention at TVA plants.


Appendix 6

Summary of OE 11720

Plant: Callaway

Date: September 25, 1999

Title: Unposted High Radiation Area Due to Inadequate Post-Job Surveys

During removal of a trash bag at the filter change area of the auxiliary building, 3 decon laborers received dose rate alarms. The immediately left the bag and notified their foreman that they were going to health physics because of the rate alarm. Each exited the RCA with 1 mrem. HP surveyed the bag and found a high radiation area. Dose rates were 300 mrem/hr at 30 centimeters, greater than 5 rem/hr on contact with the bag, and 5 rem/hr at 4 to 5 inches from the bag using a RO-2 survey meter.Follow up survey with an extendible detector dose rate instrument detected 8 rem/hr at contact and 23 rem/hr with the detector pressed into the bag. The 30 centimeter reading was 850 mrem/hr. The dose rates were not uniform around the bag.The most probable cause of the elevated dose rates is plastic and rags generated during a change out of the RCS letdown filter on 9/21/99.

Events during the filter change out: Plastic sheeting was used to drape the filter path from the filter housing to the drum. The filter housing was reading 250 rem/hr. When the filter was removed from the housing, using a long handled rod with a hook at the end, the filter slipped off the tool and dropped onto the plastic. Residual water from the filter dripped onto the plastic. After the filter was secured in the drum, dose rates were 5 rem/hr on contact.

Event Causes:

The dropped filter and RCS fluid drips were the direct cause of the high dose rates on the bag.Lack of an adequate post job survey was the direct cause of the unposted high radiation area.

Discuss post job surveys at work areas.


Appendix 7

Summary of SER 34-88

Plant: Calvert Cliffs

Date: June 21, 1988

Title: Work in Radiation Areas Subject to Changing Radiological Conditions

Two mechanics working in a valve gallery received radiation exposures of 50 mrem and 131 mrem. These exposures were much higher than anticipated for 3-5 minutes in the work area. Investigation revealed that a 70 R/hr hot spot existed about 5 feet from the work area. This hot spot developed after a routine radiation survey performed on June 9, 1988. The hot spot was a result of resin leaking through a partially open valve during a resin transfer evolution. The pre-job radiation survey did not detect the hot spot.

Prior to work, the HP technician and the mechanics discussed the radiological conditions in the work area and the work to be performed. The technician was not made aware that this work required entering the overhead area of the valve alley. The technician spot checked the valve alley from the entrance before allowing work to begin.

The mechanic had a hand held radiation dose rate instrument while in the work area, but they did not monitor it. One mechanic stated that he assumed the meter would alarm if exposure rates were too high. Upon exiting the area, the mechanics reported higher than expected exposures to the technician.

Discuss event prevention.

Discuss surveys of resin transfer paths following each resin transfer.


Handout 1

Sequoyah ALARA Planning Reports

Obtain ALARA planning reports (I:/RAD-CHEM/DATABASE/XP APR.mdb) from most recent outage for:

Refueling

Steam Generator Primary

Reactor Coolant Pump Mechanical

Seal Table


Handout 2

Visual Survey Data System Maps

View various survey maps for Watts Bar and Sequoyah located at http://tvanweb.cha.tva.gov/radchem/vsds.html

http://tvaweb.cha.tva.gov/radchem

Documents

Lesson Plan Templategonuke.org/wp-content/toolkits/Radiation Protection/chscc... · Web viewAny items removed from the reactor vessel or internals can create an airborne problem if