Time Domain Reflectometry for Evaluating Detonator Cable Assemblies in the NEP

Transcription

1 Time Domain Reflectometry for Evaluating Detonator Cable Assemblies in the NEP R. M. Morey June 14, 2005 JOWOG 9 Reading, Berkshire, United Kingdom June 22, 2005 through June 24, 2005

2 Disclaimer This document was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or the University of California, and shall not be used for advertising or product endorsement purposes.

3 UNCLASSIFIED Time Domain Reflectometry for Evaluating Detonator Cable Assemblies in the NEP JOWOG 9 Meeting at AWE UK June 22-24, 2005 Rexford M. Morey Initiation Systems Group Lawrence Livermore National Laboratory EAC-Eng-R. Morey-PI-1-6/14/2005 This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng48 UNCLASSIFIED

4 NNSA ADAPT NDE TDR Program Develop Non-Destructive Evaluation (NDE) Method to Determine the Integrity of Detonator Cable Assemblies (DCAs) in Weapons. Hardware Development: Develop Time Domain Reflectometry (TDR) methods to provide a high fidelity investigative technique for DCA integrity, that Meets the safety requirements for use on nuclear weapons. Software Development: Perform an experimental program to determine various cable insults that compromise DCA integrity in the weapon, Develop analysis software to convert TDR signal to Go/No-Go information. EAC-Eng-R. Morey-PI-2-6/14/2005

5 Experimental and Development Plan Phase I (LLNL): Proof of Concept (Finished) Develop a physical breadboard system that provides a test vehicle for the proof of concept. Perform experiments to measure and evaluate know cable insults and determine impact on DCA performance. Phase II (LLNL): Development of an Engineering Prototype (Delivery 08/05) Build an engineering prototype for extensive functional and safety evaluation. Develop analysis and operational software for TDR prototype. Phase III (Pantex): Fabrication of Production Units Vendor to build TDR production DCA testers. EAC-Eng-R. Morey-PI-3-6/14/2005

6 System Block Diagram EAC-Eng-R. Morey-PI-4-6/14/2005

7 Breadboard TDR at PSPL EAC-Eng-R. Morey-PI-5-6/14/2005

8 Breadboard TDR at PSPL (cont) EAC-Eng-R. Morey-PI-6-6/14/2005

9 Pulse Insertion Unit: Design A EAC-Eng-R. Morey-PI-7-6/14/2005

10 Good Cable: Open and Short Open Short EAC-Eng-R. Morey-PI-8-6/14/2005

11 Capacitive Discontinuity Damaged Cable Good Cable EAC-Eng-R. Morey-PI-9-6/14/2005

12 Cable Insulator Lab EAC-Eng-R. Morey-PI-10-6/14/2005

13 Insulator #1 EAC-Eng-R. Morey-PI-11-6/14/2005

14 Cable Insulting Test Plan Deform cables with metal dowels of various diameters from 1/32 to 1/4 Vary the load to inflict increasing deformation Record TDR signature Hi-pot the cable to determine voltage breakdown Purpose: Determine what cable insult leads to cable failure Develop a matrix of TDR signatures for known insults Use TDR signatures for software analysis development EAC-Eng-R. Morey-PI-12-6/14/2005

15 Software Development Analysis software (LLNL) Automatically, in real time analyze TDR signature Generate a Pass or Fail display Control software (Pantex) Control TDR cable tester Insure all safety features are in place and working Apply power to cable under test Insure PIU is properly connected Command TDR measurement Turn off power EAC-Eng-R. Morey-PI-13-6/14/2005

16 Analysis Software Considerations PFA = P(False Alarm) must be very low, because the cost of a false alarm is very high PMISS = P(Miss) must be very low, because the cost of a miss is very high Model and conduct controlled experiments with various cable geometric configurations (bends, twists, routing schemes, etc.) ==> The goal is to increase our understanding of failure modes EAC-Eng-R. Morey-PI-14-6/14/2005

17 Safety Considerations With the transformer coupling there is no DC path to the DUT for the stimulus The TDR signal is an impulse of very limited duration, ~300 ps Pulse generator is an inductor-to-ground topology (no capacitive storage) The peak current in the DUT is 50 ma, the rms current is ~350µA Both source and sampler have resistive limiters EAC-Eng-R. Morey-PI-15-6/14/2005

18 Safety Considerations Operation from an energy limited source, 2850mAh, 1.5 V x 6 AA battery pack DC current limited to 10 ma to all circuit blocks closest to the Pulse Insertion Unit On demand pass/fail test of current limiters Sampling diodes are self-biased (no DC bias) EAC-Eng-R. Morey-PI-16-6/14/2005

19 Status: June 2005 TDR Proof-of-Concept successfully demonstrated Battery-powered TDR prototype scheduled for delivery by August 2005 TDR cable tester designed for use with Nuclear Explosives Pantex fully engaged in planning TDR integration during weapon disassembly and assembly EAC-Eng-R. Morey-PI-17-6/14/2005