Technical Readiness Review of the n-3He Experiment

Seppo PenttilaORNLP-div

At SNSJan-10-2014

Seppo PenttilaORNLP-div

Technical Readiness Review of the n-3He Experiment Overall schedule

ES&H•Radiological issues•Tritium contaminated 3He gas

Flow of main tasks in the n-3He construction project

1. Design of components close to be done

2. Procurement / fabrication of components in progress

3. Testing / assembly / integration outside beamline

4. Removal of NPDGamma needs access to beamline

5. Installation in cave as soon as possible

6. IRR process1. completes the construction part of n-3He

Schedule:

Main components of n-3He experiment

Supermirror polarizer

Lead gammashielding

Solenoid

RF Spin Rotator 3He target/detector

4 x preampenclosures

Construction and Installation tasks in level 1

Preassembly

Today

Start disassemble NPDGamma

IRR

Installation Gantt chart in level 3

ES&H

Removed NPDGamma components are slightly activated

Activated especially are several Al beam windows and in some extend 48 CsI crystals.

All the removed NPDGamma components will be staged and roped in bldg 8713 for survey, disassembly, and possible shipping.

Dose Rate Calculations

We have performed preliminary dose estimates with MCNP6 using Remec’s geometry, source term, and shielding package that he used for NPDGamma.

• In NPDGamma neutrons are converted to gamma rays

• In n-3He experiment n-3He capture doesn’t produce gamma rays.

Radiation Levels - n-3He has two modes of operation

N-3He will have two modes of operation:

1.Alignment with beam – no 3He in target2.Normal production with 3He target

Dose rates have been studied for the both modes of operation

The 1st task in commissioning is alignment of the detector to beam – beam profile need tobe measured down- and upstream from the apparatuswithout target chamber and RFSR.

Neutron dose rates with 3He

Neutron dose rates with 3He

Neutron dose rates with 3He

Neutron dose rates with 3He

Neutron dose rates without 3He

Photon dose rates with/without 3He

Photon dose rates with/without 3He

Photon dose rates with/without 3He

According to these preliminary dose rate studies, the radiation levels outside the shielding meet the SNS limit.

We will complete the dose rate studies and thenthe SNS Neutronics Analysis group has to verify the results for IRR.

Tritium contaminated 3He

In experiment we are interested in reactionn +3He -> 3H + 1H

T1/2 =12.3 yr

After neutron guide neutron flux is 1011 neutrons/s- Supermirror polarizer reduces flux by 2- 5x1010 neutrons/s enter the 3He target chamber- ½-lifetime of triton is 12.3 yr- 5000 h of production

Tritium activity in chamber will be 80 mCi corresponding toabout 1018 tritons = 1.4 micro mole = 4.2 micro gr

For an upper-limit estimate for tritium amount at the end of the experiment:

How much tritium is produced ?

BL-13 flux from guide

We have to consider:

-Accidental relies of tritium into Target Hall-During experiment sensing wires can break inside the chamber

- we need to open the chamber; pump the contaminated 3He to auxiliary container at SNS/HIFR/?? to fix the problem

-When the experiment is over we want to recover 3He ($$) at USA or -Transport chamber with tritium to Univ. Manitoba / Canada for recovery.

Chamber is a strong Al vacuum chamber with sst CF flanging – beam windows1 mm thick Al. 3He gas in the chamber is at NTP.

We are in process with SNS to study issues such as;-What happens accidentally released gas-Possibility to pump contaminated 3He into a storage tank at SNS-Regulations for transportation of tritium contaminated gas inside USA and across border to Canada.

For IRR we will create a safety document to cover the tritiumissues.