Multi-layer Protection Strategy for

Manufacturing Facilities

Multi-layer Protection Strategy for

Manufacturing Facilities

Vasilis FthenakisNational Photovoltaic EH&S Assistance Center

Brookhaven National Laboratory

SSA 2001 Annual Symposium

New Orleans, LA

National Photovoltaic EH&S Assistance Center www.pv.bnl.gov

National Photovoltaic EH&S Assistance Center www.pv.bnl.gov

Preserve safe & environmentally friendly facilitiesPreserve safe & environmentally friendly facilities

– (S&E audits, SAR, HAZOP, FTA) Identify/characterize potential EHIdentify/characterize potential EH&&S hazards before full-scale S hazards before full-scale

commercialization of new technologies, processes commercialization of new technologies, processes && materials materials

– (Si, x-Si, a-Si, CdTe, CIS, CGS, GaAs, ZnP) End-of-Life PV module recycling feasibility (with DOE-SBIR)End-of-Life PV module recycling feasibility (with DOE-SBIR) Pb-free solder technology transferPb-free solder technology transfer Toxicology of new materials e.g., CdTe, CIS, CGS, (with NIEHS)Toxicology of new materials e.g., CdTe, CIS, CGS, (with NIEHS) Integrated energy-environmental-economic market penetration Integrated energy-environmental-economic market penetration &&

COCO22 reduction forecasts (MARKAL model) reduction forecasts (MARKAL model)

Sample of Hazardous Materials Used in Manufacturing

Sample of Hazardous Materials Used in Manufacturing

Material OSHA-PEL

(ppm)

ACGIH-STEL(ppm)

NIOSH-IDLH(ppm)

AIHA-ERPG-2(ppm)

OSHA-PSM-TQ

(lb)

Comments

Arsine 0.05 3 3 - 100 Highly toxic,potential carcinogen

Arsenic 0.01 mg/m3

(inorganic)5 mg/m3 Highly toxic, potential

carcinogen

Cadmiumcompounds

0.005 mg/m3

(fumes)- - NA Potential carcinogen

Carbontetrachloride

10 25 200 100 Toxic, potent greenhouse gas

Silane 5 - - - 10,000 High fire & explosion hazard

Diborane 0.1 - 15 1 Highly toxic

BoronTrifluoride

1 25 250 Toxic

Hydrogen - - - 10,000 Fire hazard

Hydrogenfluoride

3 30 20 1,000 Noxious, corrosive

Hydrogenselenide

0.05 2 150 Highly toxic, flammable

Hydrogensulfide

10 15 - 30 1,500 Toxic, flammable

Phosphine 0.3 1 50 - Highly toxic, flammable

Elements of EH&S Hazard AssessmentElements of EH&S Hazard Assessment

Process & Material Options

Exposure &ConsequenceAnalyses

Evaluation of Prevention & Mitigation Strategies

Cost-Benefit Analysis

Biomedical Research

Identification of Physical & ChemicalHazards

Dose-Response Assessment

Process LevelScreening of Hazards

R &D Hazard Hazard Hazard Identification Characterization Management

Choice of TechnologyProcess & Materials

Material Utilization

Inherently Safer OptionsInherently Safer Options

Safe Delivery, Dilute Mixtures, SDS, High Utilization, Reduced Inventories

Detection, O&M Procedures,Training, SRA, HAZOP, FTA

Accident Initiating Event

Emergency Scrubbing

External Release

HAZARD DEVELOPMENT PREVENTION/MITIGATION LAYERS

Contained Release

Human Exposure

Flow Restrictors, Auto-shut offDouble Containment

Remote Site, Separation Zones , Emergency Planning

Defense in DepthDefense in Depth

Selection of Technology, Processes and MaterialsSelection of Technology, Processes and Materials

Technologies and processes that do not require the use of large quantities of hazardous materials; especially important for new technologies

Consider:•Type & form of material used •Utilization rate•Process emissions•Life-cycle

If a hazardous material must be used, then try safer forms and minimum quantities.

Safer Material Utilization Safer Material Utilization

•Substitution (use safer materials or environmentally more benign ones)

•Attenuation (use a safer, less mobile form of a hazardous material)

•Intensification (reduce the quantity of a hazardous material in process and storage)

•Dilution (reduce its concentration) •Point-of-use generation

Alternatives need careful evaluation

Material Substitution ExamplesMaterial Substitution Examples

• Wet etching with plasma etching • Wet wafer cleaning with gas-phase cleaning

• Silane (in epitaxial Si and Si3N4 deposition) with organosilanes and chlorosilanes

• AsH3 & PH3, with TBA & TBP

• AsH3, PH3 & H2Se, with solid As, P, & Se compounds

Safer Material FormsSafer Material Forms

• Subatmospheric pressure gas sources (AsH3, PH3, BF3)

• VAC -Internally pressure regulated sources (SiH4)‡ Twofold benefit; it reduces the probability for an explosion

and the overpressure resulting from one

• For hazardous solid materials (e.g., Cd compounds) using the material in pelleted form instead of a fine (respirable size) powder, reduces the severity of exposure.

DilutionDilution

• Wafer cleaning processes that do not require concentrated chemical solutions

• Diluted inorganic hydrides reduce consequences of leaks.

• For toxic gases (e.g., PH3, B2H6), is a trade-off between frequency and maximum consequences of an incident.

• For explosive gases, the benefit of dilution is twofold; it reduces the probability for an explosion and the overpressure resulting from one.

• Productivity issues

Reduced Quantities on SiteReduced Quantities on Site

• High rate of material use & strict control of inventories.

•Deposition processes that use materials more efficiently:

(Hot-wire deposition vs. plasma-discharge deposition in a-Si;

Electrodeposition vs. spray pyrolysis in CdTe and CdS deposition).

•Higher material utilization rates offers safety advantages and lower costs; processes with low efficiency will have to be improved or unused materials be captured, purified, and reused.

Mini-Bulk or Bulk Deliveries vs. Cylinder Deliveries

Mini-Bulk or Bulk Deliveries vs. Cylinder Deliveries

• Bulk gas delivery advantages: – Better purity, lower cost, reduced probability of a leak.

• Disadvantages: – Much greater potential consequences

• The safety issue is controversial• A decision is facility specific;

– it depends on facility location and size.

• Standards/Guides applicable to bulk SiH4

– NFPA 318, FM, SEMI, CGA

Choice of TechnologyProcess & Materials

Material Utilization

Inherently Safer OptionsInherently Safer Options

Safe Delivery, Dilute Mixtures, High Utilization, Reduced Inventories

Detection, O&M Procedures,Training, SRA, HAZOP, FTA

Accident Initiating Event

Emergency Scrubbing

External Release

HAZARD DEVELOPMENT PREVENTION/MITIGATION LAYERS

Contained Release

Human Exposure

Flow Restrictors, Auto-shut offDouble Containment

Remote Site, Separation Zones , Emergency Planning

Prevention of Initiating EventsPrevention of Initiating Events

Once specific materials and systems have been selected, strategies to prevent accident-initiating events need to be evaluated & implemented.

• US facilities that handle listed hazardous chemicals in quantities above certain thresholds are required to comply with

OSHA Process Safety Rule (PSM)

EPA Risk Management Program (RMP).

Some Listed materials:

AsH3, BCl3, BF3,B2H6, H2Se, H2S, HF, NH3 PH3, SiH2Cl2, H2, SiH4, SiHCl3

Components of the EPA -RMPComponents of the EPA -RMP

1. Hazard Assessment1. Hazard Assessment Analyze transientsAnalyze transients Review documentation of past releasesReview documentation of past releases Identify worst-case & likely release scenariosIdentify worst-case & likely release scenarios Estimate maximum impact zonesEstimate maximum impact zones

2. Accident Prevention2. Accident Prevention Safety precautions and management systemsSafety precautions and management systems Operating procedures.Operating procedures. Employee safety trainingEmployee safety training Process Hazard AnalysisProcess Hazard Analysis Safety auditsSafety audits · Incident investigation & report · Incident investigation & report Control and mitigation systemsControl and mitigation systems

3. Emergency Preparedness and Response3. Emergency Preparedness and Response

Prevention of Initiating EventsPrevention of Initiating Events

Be Proactive!Be Proactive! Conduct Process Hazard Analysis (PHA) even when it is not Conduct Process Hazard Analysis (PHA) even when it is not

required. required. PHA must be formal & rigorous.PHA must be formal & rigorous. PHA focus on equipment, instrumentation, utilities, human PHA focus on equipment, instrumentation, utilities, human

action, external factors that may impact a process & cause an action, external factors that may impact a process & cause an accident initiating event. accident initiating event.

Example: SAR conducted proactively as a result of a self-Example: SAR conducted proactively as a result of a self-appraisal at NRELappraisal at NREL

Safety Analysis Review (SAR)Safety Analysis Review (SAR)

–Reviewed operations

–Identified 30 potential accident-initiating events

–Characterized risks

–Implemented administrative and engineering controls to

ensure safe operation, e.g.

•Control systems to avoid cross-contamination, elimination of single-point failures, safeguards against process deviations and monitoring systems.

• Safe operating & maintenance procedures & training.

Risk Assessment MatrixRisk Assessment Matrix

PROBABILITY

CONSEQUENCE

AFrequent

BReasonblProbable

COccasional

DRemote

EExtremely

Remote

FImpossible

ICatastrophic

HIGH RISK

IICritical

LOW

IIIMarginal

MODERATE

IVNegligible

ROUTINE

Risk Assessment MatrixRisk Assessment MatrixEvent probability classification

A: Frequent (>1.0). Likely to occur many times during the life cycle of the system(test/activity/operation).

B: Reasonably probably (0.1-1.0). Likely to occur some time during the life cycle of the system.C: Occasional (0.01-0.1). Likely to occur some time during the life cycle of the system.D: Remote (10-4-10-2). Not likely to occur in the life cycle of the system, but possible.E: Extremely remote (10-6-10-4). Probability of occurrence cannot be distinguished from zero.F: Impossible (<10-6). Physically impossible to occur.

Hazard consequence classification I: Catastrophic (loss >$1 million). May cause death or system loss. II: Critical ($100,000-$1 million). May cause severe injury or occupational illness or minor systemdamage.

III: Marginal ($10,000-$100,000). May cause minor injury, occupation illness, or system damage. IV: Negligible (<$10,000). Will not result in injury, occupational illness, or system damage.

Risk categoryRoutine: Risk no different from those experienced by any individual in his or her daily life.

Low risk: Events may have impact within a facility but little or no impact to adjacent facilities,public health, or the environment.

Moderate risk:Events have potential impacts within the facility but at most only minor impacts off site.High risk: Events have the potential for on-site and off-site impacts to large numbers of persons or

major impacts to the environment.

Prevention Layers Failed!Prevention Layers Failed!

Prevention/Minimization of Releases

Prevention/Minimization of Releases

•Implement safety options to suppress a hazard when an accident-initiating event occurs•Prevention options to enhance the safety of compressed-gas cylinder systems:

a) Continuous monitoring, early detection

b) System integrity, fail-proof design

c) Outside storage or indoors explosion-proof banker

d) Remotely operated cylinder valves

e) Automated purging

f) Flow restrictors

g) Double containment

e) Redundancy of critical systems

System IntegritySystem Integrity

Operational hazards are greatly reduced by certain features that improve the system's integrity, e.g.,

•properly designed, constructed, and vented enclosures,

•welded piping joints,

•ventilation system back-up,

•alarms and interlocks for process chambers.

Outside StorageOutside Storage

• Outside storage bunkers for toxic and pyrophoric gases reduce occupational risks associated with accidental releases.

Indoors BunkersIndoors Bunkers

• Silane cylinders can be kept indoors in explosion-proof bunkers (with relief through the ceiling); however, this is an expensive option.

Remote OperationRemote Operation

• Remotely operated cylinder valves enhance safety by separating workers from hazards and allowing for remote shutdown in an emergency.

Automated PurgingAutomated Purging

• Manual purging is demanding on the operator.

• Automated purge systems reduce actions needed to complete a purge procedure, and reduce potential for human errors.

Continuous Toxic Gas Monitoring Systems

Continuous Toxic Gas Monitoring Systems

• Integrate toxic-gas detection into gas-handling systems and process tools for early warning and source & process shut down

• Set audible and visible alarms at 1/2 TLV

Flow RestrictorsFlow Restrictors

• Flow-restricting orifices (RFO) in cylinder valves for highly toxic and pyrophoric gases (e.g., AsH3, PH3, SiH4).

• RFO can reduce the flow out of an open cylinder-valve up to 100 times; they provide superb passive flow-reduction.

Double ContainmentDouble Containment

• Double co-axial distribution lines and raceways. • Double-wall storage.• Secondary enclosures to contain toxic emissions and

divert to pollution-control equipment.

Redundancy in Critical SystemsRedundancy in Critical Systems

Redundancy in Critical SystemsRedundancy in Critical Systems

• If a hazard analysis identifies accidents that can be caused by the failure of a single component, redundant components should be installed

• Examples of critical components:Flow-regulators, valves, exhaust fans, pumps, compressors.

• Redundant systems must be completely independent

• Examine conditions which may adversely affect a given layer of defense at the same time that they produce a safety challenge to that layer

(Such conditions in complex systems can be studied with Fault Tree Analysis)

Control and Minimization of Releases to the EnvironmentControl and Minimization of Releases to the Environment

• SCBA, spill control, safety equipment for quick response in all areas where there is potential for an accidental release.

• Accidental release containment and control equipment (e.g., wet or dry scrubbers)

Prevention and Minimization of Human Exposures

Prevention and Minimization of Human Exposures

• Remote location, exclusion zones• Early warning systems• Emergency preparedness and response programs• Medical preparedness

Choice of TechnologyProcess & Materials

Material Utilization

Medical Surveillance Biomonitoring)Medical Treatment

Multi-Layer Protection for Occupational Safety

HAZARD DEVELOPMENT PREVENTION/MITIGATION LAYERS

Employee Exposure

OSHA/Industry Employee ProtectionPrograms, e.g., air monitoring,ventilation, SOP

Safer Delivery, SDS, High Utilization, Reduced Pressure

Inherently Safer OptionsInherently Safer Options

Consequences

CONCLUSIONCONCLUSION

• Accidental releases of hazardous gases and vapors can cause occupational hazards.

• Prevent and minimize accidental releases of hazardous gases by choosing safer technologies, processes, and materials, using materials more efficiently and in safer forms.

• Use safety systems and procedures to reduce risks that could not be avoided with process and material selections.

• A systematic approach assists management to minimize EH&S risks

We are all partners in EH&S !Working together means winning together

We are all partners in EH&S !Working together means winning together

www.pv.bnl.gov

Point-of-use GenerationPoint-of-use Generation

Point-of-use generation of hazardous materials reduces Point-of-use generation of hazardous materials reduces the hazards of both transportation and storage on-site.the hazards of both transportation and storage on-site.

e.g., Bell Labs on-demand arsine generators e.g., Bell Labs on-demand arsine generators give better give better purity than compressed-gas cylinderspurity than compressed-gas cylinders

Risk Analysis ResultsRisk Analysis Results

Probability Consequence RiskTransient description I ER R O RP F N M C CA R L M H

Intralaboratory transportation accident * * *Missing washer in HCI or H2Se cylinder * * *Forgetting washer/gasket in gasketed gasconnection

* * *

Attempts to open sticky cylinder capToxic/pyrophoric liquid bubbler put inbackwardsToxic/pyrophoric liquid bubbler leakoutside delivery systemLeak of air in vacuum pumpFaulty seals connecting reactor vessel tosystemRupture of quartz reactor vesselHydrogen leak in purifierLoss of process control and simultaneousfailure of scram unit, exhaust scrubber, orcylinder valveHigh winds and tornadoes