1. ODH Risk Assessment underground gallery B887-EHN1
On behalf the working group EN - EP Safety offices
Marine Ellin, Alexandre Desmarest, Katalin Nikolics, Simon Cherault .

2. Risk assessment for the underground gallery of EHN1 – B887
Context: EHN1 safety file edition (887 existing part)
1st step: Identification of gas users (NA 61, SHIP, RE 21, RD 51) and gas suppliers in the area (EN-EA, TE-CRG)
2nd step: Identification of type of gas: lines, Dewars, bottles, pressure, quantity.
3rd step: Assessment of the risk: leak scenarios, air flow, condition
of the pipelines
4th step: Engineering check with HSE-XP and main stakeholders
5th step: Approbation of the mitigation measures
Risk analysis:

3. Risk assessment for the underground gallery of EHN1 – B887
Galleries volume:
Longitudinal :360m x 3m x 2.5m yielding a volume of 2700 m3
Transversal:7 x (45m x 3m x 2.5m) adding thus a volume of m3
Access to gallery

4. Risk assessment for the underground gallery of EHN1 – B887
CO2 Gas Bottles
974 m3
Lar Dewar
6000 l
LN2 Dewar l
10 bar

5. Gas network in the gallery
Air circulation : 0 m/s in the longitudinal tunnel and transversal parts

6. Current fixed ODH detection
Designed for ATLAS exp not anymore in place

7. Scenario Leak size Small (5mm2 ) 75.5 h Medium (20mm2 ) 19 h
Leak on N2 pipe (worst case)
Leak on CO2 pipe
No remote analogic monitoring on N2 DEWAR consumption thus undetectable
Leak size N2
Time to 18% O2
CO2
Time to 19.5% O2 (toxicity)
Small (5mm2 )
75.5 h
62 days longitudinal gallery
7.8 days transversal gallery
Medium (20mm2 )
19 h
16 days longitudinal gallery
48 h transversal gallery
Large (500mm2 )
45.8 min
16 hours longitudinal gallery
2 hours transversal gallery
No access control, lack of data on the exposition
Work in the gallery : EN-CV, EN- EL, EP, IT, construction, maintenance

8. Risk matrix Gravity of damage for human body
Exposure average amount of people exposed for a year
Minimal
Slights injuries
Low
Temporary reversible illness no hospitalization
Medium
Temporary reversible illness with hospitalization
High
Death
Permanent disability
Irreversible illness
Permanent
People exposed to the risk once-twice every day
Often
People exposed to the risk once-twice every weeks
Work in gallery EHN1
People exposed to the risk once-twice every month
Exceptional
People exposed to the risk once-twice a year

9. Proposed solutions Action Observation S Close access
Reliability
Cost
Timing
Ease of implementation
Remaining risk rating
Observation S
Close access
Need to access the gallery for operationnal purpose
P-O
Portable ODH and CO2 detectors for every workers + signs + IMPACT
Do not cover the CO2 aspect which remains high in transversal galleries T
Ventilation in transversal and longitudinal gallery + ODH fix detector + CO2 fix detectors+ Alarm
Technical specification need to be done O
Access control for galleries
control the awareness; not the PPEs
T-O
Periodic non-destructive verification of the pipelines
Assessment to be performed after each big work in the gallery
Monitoring automatic on the Dewar and gas bottle
Difference between small leak and normal consumption

10. Thanks !