Tritium in The Demin Water System --

An IE Bulletin 80-10 Challenge

Ken SejkoraEntergy Nuclear Northeast – Pilgrim Station

Presented at the 12th Annual RETS-REMP WorkshopAtlantic City, NJ: 24-26 Jun 2002

Problem Identification Detected tritium in October sample from

station heating system: 3E-6 uCi/mL Previous samples historically showed

NDA; follow-up sampling indicated upward trend

Response delayed by lack of on-site H-3 analysis capabilities… delays through vendor lab

Initiated IE80-10 sampling of interfacing systems

Problem Scoping IE80-10 sampling detected H-3 in

demineralized water system: 9E-6 uCi/mL DW system analyzed monthly for gamma;

no previous H-3 analysis Follow-up sampling indicated upward trend Initially suspected backflow from interfacing

system; extensive sampling in various legs of DW system yielded ~ equal concentrations… no smoking gun!!

Problem Assessment DW used as makeup to clean systems (diesel

generators, stator cooling); top off lead-acid batteries (mixed waste?); mix chemical standards for clean-area use

Lack of previous H-3 sampling of DW system gave us nothing to compare to… i.e., had the problem existed before, or was it “new”?

Review of system design revealed shared vent line with condensate storage tanks… could we exchange activity through a vent line? H-3…YES!

PNPS has had an eight-fold increase in reactor coolant boron and tritium in past 2 years from control blade leakage… coincidence?

Condensate Storage Tank(one of two)

Demin Water Storage Tank

16” Underground Ventilation Header to Radwaste Building

12” Vent Pipe Internal to CST

4” Vent Pipe Internal to DWST

El. 40’6”

El. 22’2”

275,000 gal.

50,000 gal.

Diagram of Tank Ventilation Cross-connection

Condensate Storage Tanks Two tanks at 275,000 gal each Tritium Concentration = 7E-2 uCi/mL,

total H-3 inventory in CST = 146 Ci Average daily water flux = 33,000

gal/d, 4,400 cu.ft/day Nominal temperature at 80 deg.F,

airborne H-3 = 1.8E-6 uCi/cc air Daily airborne tritium flux = 220

uCi/day

Demin Water Storage Tank One tank at 50,000 gal Tritium Concentration = 2E-5 uCi/mL,

total H-3 inventory in DWST = 0.0038 Ci

Average daily makeup = 2,300 gal/day, 308 cu.ft/day

Nominal temperature ~ outside ambient (45 deg. F in winter)

DWST is heat sink compared to 80 deg. CSTs… effective condensation trap!!

Air Exchange From CSTs

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Proposed Solution Remove source term to DWST by

removing ventilation cross-tie Maintain venting of CSTs to radwaste

building, capture as monitored release Vent DWST to atmosphere, as

radiological concerns disappear following modification

Cannot effectively remove H-3 through treatment… dilution, bleed & feed

Radiological concerns following mod?

Condensate Storage Tank(one of two)

Demin Water Storage Tank

16” Underground Ventilation Header to Radwaste Building

12” Vent Pipe Internal to CST

4” Vent Pipe Internal to DWST

El. 40’6”

El. 22’2”

275,000 gal.

50,000 gal.

Capped End DWST Vent open to Underground Valve Pit

Modified Tank Ventilation Scheme

Projected Dose Consequences Catastrophic failure of DWST, entire

volume released in 20 min as liquid effluent release: 7E-6 mrem to maximum-exposed individual

Evaporation of tank volume released as airborne effluent following vent modification: 6E-6 mrem to maximum-exposed individual

Questions Raised: IE80-10 Do we control station heat and demin systems

as ‘contaminated’ systems… negligible dose impact, impossible to measure activity by normal survey methods; posting requirements?

What LLDs do we need to achieve to call the system “clean”? Effluent? Environmental?

ALARA considerations… negligible dose consequences to leave as is (DWST concentration is at EPA drinking water standard); real dose is incurred to fix the “problem”

Summary Don’t overlook the obvious! Tritium can pose special concerns What other systems could have similar cross-

ties? Which LLDs does one use to declare victory

and call a IE80-10 system “clean”? How much time, effort, money, and REAL

DOSE should be expended to fix a problem that has no dose impact?