hazard categorization threshold quantities for tritium...2 hazard categorization threshold...

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Hazard Categorization Threshold Quantities for Tritium

William C. Walker

Nuclear Facility Safety Engineer

Nuclear and Radiological Protection Division

Oak Ridge National Laboratory

May 16, 2018

2 Hazard Categorization Threshold Quantities for Tritium (May 2018)

Timeline of Tritium TQs

History of HC-2 and HC-3 TQ values for Tritium in DOE-STD-1027

Version

Category 2

TQ

Category 3

TQ Comments

DOE-STD-1027-92

(1992)

3.0E+05 Ci

3.0E+01 g

1.0E+03 Ci

1.0E-01 g

Tritium threshold was lowered from its calculated

value to 1000 curies based on a recommendation of

the Tritium Task Force.

DOE-STD-1027-92 CN-1

(1997)(Unch.)

1.6E+04 Ci

1.6E+00 g

TFG requested Tritium Cat 3 TQ be calculated same

as all other radionuclides.

NNSA Supplemental

Guidance (2014)(Unch.) (Unch.)

NNSA published updated TQs for all DOE-STD-1027

radionuclides except for Tritium.

DOE-STD-1027-DRAFT

(2018)(Unch.) (Unch.) Updated TQs for +1,250 radionuclides, except tritium.


Comparison of Current and Updated Cat 2 Tritium TQ

CALCULATION OF HAZARD CATEGORY 2 TRITIUM TQ

[per NRC dose exposure methodology]

ICRP Pub-119

DC

(Sv/Bq)

DOE-EH-0071

DC

(rem/mCi)

Final DC

(rem/Ci)

Release

Fraction

Skin

Absorption

Factorc/Q

(s/m3)

BR

(m3/s)

Final TQ

(Ci)

Calc. Current TQ

(w/ Skin Abs. Factor)6.30E-05 6.30E+01 1 50% 1E-04 3.5E-04 3.02E+05

Published TQ

(DOE-STD-1027-92 CN-1)3.00E+05

Updated TQ using NRC

methodology2.60E-10 9.62E+02 1 0% 1E-04 3.33E-04 3.12E+04

% Change -89.6%

1,472% increase in the tritium Dose Coefficient!

NRC & EPA use RFtritium=0.5

TFG recommendation


Comparison of Current and Updated Cat 3 Tritium TQ

CALCULATION OF HAZARD CATEGORY 3 TRITIUM TQ

[per EPA dose exposure methodology]

ICRP Pub-119

DC

(Sv/Bq)

ICRP Pub-30

ALI

(Bq per 0.05 Sv)

Final DC

(rem/Ci)

Release

Fraction

Skin

Absorption

Factor

/Q

(s/m3)

BR

(m3/s)

Final TQ

(Ci)

Calc. Current TQ

(w/ Skin Abs. Factor)3.00E+09 6.17E+01 0.5 0% 7E-02 2.7E-04 1.68E+04

Published TQ

(DOE-STD-1027-92 CN-1)1.60E+04

Updated TQ using NRC

methodology2.60E-10 1.52E+02 0.5 0% 7E-02 3.33E-04 5.45E+03

% Change -66.0%

146% increase in the tritium Dose Coefficient!

Agrees with NRC & EPA!


Chronology of Tritium Inhalation Dose Coefficients

Category 2 Tritium Inhalation Dose Coefficients

Publication DOE-EH-0071 ICRP Pub-72/119

Year 1988 1996 (Pub-72) | 2012 (Pub-119)

Bounding Chem/Phys. Form Tritiated Water Tritiated Water"S" Particulate Lung

Clearance

ALI (Bq per 0.05 Sv) -- -- --

DC (rem/mCi) 6.30E-05 -- --

DC (Sv/Bq) -- 1.80E-11 2.60E-10

FINAL DC (rem/Ci) 63.0 66.6 962

DCnew:DCold 14.27

Category 3 Tritium Inhalation Dose Coefficients

Publication ICRP Pub-30 ICRP Pub-68/119

Year 1979 1994 (Pub-68) | 2012 (Pub-119)

Bounding Chem/Phys. Form Tritiated Water Tritiated Water OBT Gas

ALI (Bq per 0.05 Sv) 3.00E+09 -- --

DC (rem/mCi) -- -- --

DC (Sv/Bq) -- 1.80E-11 4.10E-11

FINAL DC (rem/Ci) 61.7 66.6 152

DCnew:DCold 1.46

Water vapor is no longer the

bounding dose exposure case!

1 mm Particulate

Organically Bound Tritium


Summary• Tritium TQs will remain the same in DOE-STD-1027-DRAFT (2018).

• Not using updated TQs at this time.

• Updated TQs for tritium will decrease upon incorporation into future revision to DOE-STD-1027.

• Cat 2: -89.6%

• Cat 3: -66.0%

• Lower TQs attributed to tritiated water vapor as no longer being the bounding inhalation exposure case.

• Category 2: 1mm particulate (“Slow” Lung Clearance Type)

• Category 3: Organically Bound Tritium

• Issues for Consideration– Current and draft DOE-STD-1027 specify RFtritium = 1.0 for Category 2.

• RFtritium = 0.5 per NRC and EPA guidance.

– Is skin absorption still an issue? • Bounding exposure cases no longer involve tritiated water.


THANKS!

• Questions???

hazard categorization threshold quantities for tritium...2 hazard categorization threshold...

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